In unit 4, we learned all about toxins. The definition of a toxin is a substance that interacts with a living thing and causes harm. Toxins can enter the body and will often react with water. They can be molecular, ionic, or metallic-bonded substances.
When we first started unit 4, we learned what it means to interpret a chemical equation. That includes basically looking at an equation and the phase changes (the italicized letters next to chemical compounds) in it and writing in words what's happening. This could possibly sound like "solid ___ reacts with an aqueous ___solution to form solutions of ___ and ___." The italicized letters can act as clues to whether a reaction is a physical or chemical change.
A huge part of this toxins unit was balancing equations. It's crucial for a chemical equation to be balanced on both sides, otherwise the reaction will be unstable. A lot of reactions will produce toxic substances. Not only do equations need to be balanced for the safety of the chemists, but also to abide by the law of conservation of mass, which states that no atoms can be lost or gained. Balancing equations and predicting products go hand in hand; there are four different types of reactions: combination, decomposition, single exchange, and double exchange. If ever an atom moves places between the reactant side and the product side, you have to make sure it's present in equal quantities on both sides.
Obviously, we also learned about toxicity in this unit. All substances can be toxic if ingested in large enough qualities, and the amount of substance needed to kill an organism or poison it is called the LD-50. LD stands for "lethal dose". To calculate how much substance you need to harm an organism of a certain weight in pounds, convert those pounds to kilograms and multiply by the LD-50.
pH is important to consider when dealing with contaminated substances or substances which you don't know the toxicity of. On a logarithmic scale, anything with a pH of lower than 7 is an acid, and anything above 7 is a base. 7 is neutral. PH is determined by the concentration of hydrogen and hydroxide ions in a solution. An acid or base can be diluted with water, and certain mL of water can decrease the acidity or basicness by tenfold.
The final, and possibly hardest, skill that we learned in this unit was stoichiometry, which uses coefficients in BALANCED chemical equations to determine the number of moles of a substance. By constantly converting moles to grams and back to moles, you can find out how much reactant is needed to make a certain amount of product and vice versa. You can also figure out limiting reactant, a reactant that puts a limit on how much product can be made.
Problems:
Jogkvsjdajfsk (to be added soon)
Friday, December 14, 2012
Monday, December 10, 2012
Disappearing Spoon, Ch. 15-17
In chapter 15, I read about William Crookes and his discovery of selenium, an element that, like most in the periodic table, is toxic in large doses. It can cause physical harm including but not limited to fevers and sores, and it can give one a kind of high if ingested. There were farmers and ranchers in Crookes' time whose cattle were prone to eating weeds rich in selenium compound. As one could guess, this harmed the cattle and the animals had to be monitored carefully. Go back to the mentioning of selenium giving highs; it was thought in those times that people could go mad if they took in a lot of selenium. People assumed that this was the cause of Crookes' "madness" that he displayed by abandoning his science to pursue a religious life path. His choice was made after the death of his brother. While it's possible that his work with selenium could have poisoned William, I think that this was a good example of what grief over death can do to a person. I also read about William Röntgen, who discovered x-rays.
In chapter sixteen, Kean talked about a man named Robert Scott who took a few of his buddies with him to the South Pole. The explorers had quite a bit of tin with them when they were on their way, and as they got closer to Antarctica, the tin began to rust. Unlike iron rust, tin rust is white. However, like anything else that can rust, the tin grew fragile. One could imagine that things began falling apart on the journey, perhaps malfunctioning. A kerosene leak along the way claimed Scott's life, and his buddies had to turn back without him. Cold conditions do strange things to metals. An example I used to relate to this chapter is how cold temps drain battery life. It was highly likely that some disaster would intervene with Scott's goal.
Chapter 17 went into greater detail about the story behind a man whose name I've actually heard a few times in school. Supposedly, Donald Glaser invented a "bubble chamber" while sitting in a pub, and the actions that he performed with his invention apparently helped him see tiny, tiny things called "kaons", "muons", and "pions". I admit, I have no idea what those are. This assumption about Glaser is false, nothing more than a tall tale. However, his bubble chamber did make one thing clear. I read in this chapter that bubbles form around the imperfections of something like a glass. Regardless of carbonation, a glass of wine or champagne will be bubbly because there are microscopic cracks in the wine glass.
In chapter sixteen, Kean talked about a man named Robert Scott who took a few of his buddies with him to the South Pole. The explorers had quite a bit of tin with them when they were on their way, and as they got closer to Antarctica, the tin began to rust. Unlike iron rust, tin rust is white. However, like anything else that can rust, the tin grew fragile. One could imagine that things began falling apart on the journey, perhaps malfunctioning. A kerosene leak along the way claimed Scott's life, and his buddies had to turn back without him. Cold conditions do strange things to metals. An example I used to relate to this chapter is how cold temps drain battery life. It was highly likely that some disaster would intervene with Scott's goal.
Chapter 17 went into greater detail about the story behind a man whose name I've actually heard a few times in school. Supposedly, Donald Glaser invented a "bubble chamber" while sitting in a pub, and the actions that he performed with his invention apparently helped him see tiny, tiny things called "kaons", "muons", and "pions". I admit, I have no idea what those are. This assumption about Glaser is false, nothing more than a tall tale. However, his bubble chamber did make one thing clear. I read in this chapter that bubbles form around the imperfections of something like a glass. Regardless of carbonation, a glass of wine or champagne will be bubbly because there are microscopic cracks in the wine glass.
Thursday, December 6, 2012
Unit 4, Lesson 26
Reactants hardly ever combine in the ratios that we see them in in chemical reactions. It's almost like the textbook writers made up problems for students to solve! Haha, fancy that. No, back to serious business, ususually there's more of one reactant than is required to burn up the other. Because of this, chemical reactions can be short-lived. The amounts of products depends on how much reactant is present. You can only have as much product as your limiting reactant will allow. The amount of product that a limiting reactant comes up with is called the % yield.
Extra notes / Practice Problems:
Extra notes / Practice Problems:
Unit 4, Lesson 25
In order to determine the mass of product produced by a certain mass of reactant (and vice versa), it is necessary to convert mass to moles and then back to mass. This process is called "the mole tunnel". The balanced chemical equations are written in moles--how is that known? Because the coefficients represent the number of moles of reactant. Sometimes a problem tells us how many grams of each reactant we have, and we have to find the mass of the precipitate or product. Sometimes, we know the mass of the product, and we have to find the mass of one of the reactants. This is where I, and a lot of others, found out that stoichiometry isn't all that easy!
Practice Problems:
Practice Problems:
Unit 4, Lesson 24
One can remove harmful substances from a water source by precipitating harmful ions from it. How does one do that, exactly? It's more of a question of how much of two reactants are needed to achieve a solid precipitate, and to answer that question, mole ratios come into play. The ratios can be identified by coefficients, the big numbers before compounds in a chemical equations. Those coefficients tell you how many moles of a certain substance are present in a reaction. They can be read by "for every __ mole(s) of reactant 1, there are __ mole(s) of reactant 2." You can also say "for every __ mole(s) of reactant one (or 2), there are __ mole(s) of product one (or two)." Sometimes we aren't given equal amounts of reactants in a reaction. In this case, one runs out first, and that reactant is called the limiting reactant. The one left over is the excess reactant.
Practice Poblems:
A convenient photo has appeared!
Practice Poblems:
A convenient photo has appeared!
Unit 4, Lesson 23
In a precipitation reaction, an aqueous solution reacts with a solution that isn't very soluble, and when combined, a solid product is formed. Precipitation reactions are double exchange reactions and their reactants are usually ionic compounds. Compounds that aren't very soluble will precipitate from aqueous solutions and show up in the product half of a chemical equation. There is a chart that says what compounds are soluble (represented by an 'S') and which compounds are not ('N'). Insoluble compounds are precipitates. There are precipitates in our own bodies: bones, teeth, and kidney stones. All three of these are made from some kind of calcium compound.
Problems:
3.) Explain what a spectator ion is. A spectator ion is an ion that is noted in a chemical equation but doesn't exactly contribute to the equation itself. More, it just kind of floats around. Or, as Ms. McDowell would say, it "chills in the beaker" with the other compounds.
4.) Which ionic solids are soluble in water? (answers in bold)
LiNO3 KCl MgCl2 Ca(OH)2 RbOH
CaCO3 Li2CO3 PbCl2 AgCl
Problems:
3.) Explain what a spectator ion is. A spectator ion is an ion that is noted in a chemical equation but doesn't exactly contribute to the equation itself. More, it just kind of floats around. Or, as Ms. McDowell would say, it "chills in the beaker" with the other compounds.
4.) Which ionic solids are soluble in water? (answers in bold)
LiNO3 KCl MgCl2 Ca(OH)2 RbOH
CaCO3 Li2CO3 PbCl2 AgCl
Monday, December 3, 2012
Disappearing Spoon, Chapters 13-14
Chapter 13:
Metals that we might find petty today were very valuable in the past. Two such metals are aluminum and bronze. Bronze stole a bit more of the spotlight when Prince Midas of Turkey discovered the secret to forging it from tin and copper. (Tin? Sounds weak, doesn't it? Maybe that's why bronze metals are the most unappreciated ones.) Perhaps because bronze was so closely associated with Midas, many considered it to be the most valuable and sought-after metal in the world. They were rather excited, as well, when the prince discovered to different colors of lead--ooh~~~~! After the fall of bronze, aluminum rose up and made people's eyes sparkle. Chapter 13 talked about gold a lot, even though it's been mentioned throughout the book several times already. Anyone who's paid a lick of attention in history already knows that gold was made famous partially because of gold rushes worldwide. A lot of people seem to think that gold is one of those motherloads, like oil, that hides in the crevices of hard rocks. Gold ore? Well, actually, since gold doesn't bond with any element other than tellurium, it's typically found solidly by itself. That's why people panned for it. When it does bond with tellurium, metals with strange names result.
Chapter 14:
A man named Johann Wolfgang von Goethe might make you think of a composer. But he was a writer, and like anyone who can put thoughts on paper, some of his inner workings were quirky. He proposed a lot of statements about colors. He claimed that color group AB, when added to group CD, would create the reaction AB + CD --> AD + BC. Look familiar? Not sure if it exactly ties into what we're learning in chem. right now, but that smells like a double exchange reaction to me! Maybe Goethe's mind was just very colorful, or maybe he just wasn't looking into anything that anyone cares about. I say this because Sam Kean doesn't seem very, well, keen on Goethe's story. He doesn't consider him legitimate. Chapter 14 also talked about pens, which at one time were extremely valuable. Like the apple products of today, and how there always seems to be a new one, many pens came out in a consecutive row and people felt compelled to buy them.
...The day I see a pen with a touch screen, I will be astonished.
Metals that we might find petty today were very valuable in the past. Two such metals are aluminum and bronze. Bronze stole a bit more of the spotlight when Prince Midas of Turkey discovered the secret to forging it from tin and copper. (Tin? Sounds weak, doesn't it? Maybe that's why bronze metals are the most unappreciated ones.) Perhaps because bronze was so closely associated with Midas, many considered it to be the most valuable and sought-after metal in the world. They were rather excited, as well, when the prince discovered to different colors of lead--ooh~~~~! After the fall of bronze, aluminum rose up and made people's eyes sparkle. Chapter 13 talked about gold a lot, even though it's been mentioned throughout the book several times already. Anyone who's paid a lick of attention in history already knows that gold was made famous partially because of gold rushes worldwide. A lot of people seem to think that gold is one of those motherloads, like oil, that hides in the crevices of hard rocks. Gold ore? Well, actually, since gold doesn't bond with any element other than tellurium, it's typically found solidly by itself. That's why people panned for it. When it does bond with tellurium, metals with strange names result.
Chapter 14:
A man named Johann Wolfgang von Goethe might make you think of a composer. But he was a writer, and like anyone who can put thoughts on paper, some of his inner workings were quirky. He proposed a lot of statements about colors. He claimed that color group AB, when added to group CD, would create the reaction AB + CD --> AD + BC. Look familiar? Not sure if it exactly ties into what we're learning in chem. right now, but that smells like a double exchange reaction to me! Maybe Goethe's mind was just very colorful, or maybe he just wasn't looking into anything that anyone cares about. I say this because Sam Kean doesn't seem very, well, keen on Goethe's story. He doesn't consider him legitimate. Chapter 14 also talked about pens, which at one time were extremely valuable. Like the apple products of today, and how there always seems to be a new one, many pens came out in a consecutive row and people felt compelled to buy them.
...The day I see a pen with a touch screen, I will be astonished.
Friday, November 30, 2012
Unit 4, Lesson 22
Titration is the process of measuring the concentration of a strong acid in a water solution by using an indicator and adding a base to neutralize it. As stated before, neutralization reactions result in a salt and water being produced. After titration, when a point of equality is reached, there are equal moles, equal volumes, and equal molarities of the acid and the base. Get this: if you really know what you're doing, you can completely neutralize an acid with a base (or vice versa) and get a solution safe enough to drink. Granted, no one would recommend you try that at home, or even in a chemistry classroom.
If the molarity of the acid or the base is known, the molarity of the other can be found. It's crucial to find out the concentration of H+ ions and know that that number is equal to the concentration of OH- ions. Those numbers can then be divided by the volume (in L) of the substance with the unknown molarity. (If that doesn't make much sense, see the problems below)
Problems:
3.) How many mL of 0.1 M NaOH would be needed to neutralize 2.0 L of 0.050 M HCl?
First, know that 2.0 L = 2,000 mL.
0.050 M / 2,000 mL = 0.1 M / x mL
0.050 M( x mL) = 0.050x
2,000 mL( 0.1 M) = 200
200 / 0.050 = 4,000 mL
It would take 4,000 mL of NaOH to neutralize the HCl.
Another way to look at this is to realize that the molarity of the HCl is 1/2 the molarity of the NaOH solution. This means you can convert the HCl volume into mL (2,000 mL) and multiply that by 2 to get 4,000 mL.
5.) A student mixes 100 mL of 0.20 M HCl with different volumes of 0.50 M NaOH. Are these final solutions acidic, basic, or neutral?
a.) 100 mL of 0.20 M HCl + 20 mL of 0.50 M NaOH Acidic (because there's more of the solution with the lower molarity and that overpowers the base)
b.) 100 mL of 0.20 M HCL + 40 mL of 0.50 M NaOH Neutral (there is enough base to neutralize the acid, despite their different molarities)
c.) 100 mL of 0.20 M HCl + 60 mL of 0.50 M NaOH Basic (if 40 is the neutral point, anything above that as far as the NaOH is concerned should be basic.)
If the molarity of the acid or the base is known, the molarity of the other can be found. It's crucial to find out the concentration of H+ ions and know that that number is equal to the concentration of OH- ions. Those numbers can then be divided by the volume (in L) of the substance with the unknown molarity. (If that doesn't make much sense, see the problems below)
Problems:
3.) How many mL of 0.1 M NaOH would be needed to neutralize 2.0 L of 0.050 M HCl?
First, know that 2.0 L = 2,000 mL.
0.050 M / 2,000 mL = 0.1 M / x mL
0.050 M( x mL) = 0.050x
2,000 mL( 0.1 M) = 200
200 / 0.050 = 4,000 mL
It would take 4,000 mL of NaOH to neutralize the HCl.
Another way to look at this is to realize that the molarity of the HCl is 1/2 the molarity of the NaOH solution. This means you can convert the HCl volume into mL (2,000 mL) and multiply that by 2 to get 4,000 mL.
5.) A student mixes 100 mL of 0.20 M HCl with different volumes of 0.50 M NaOH. Are these final solutions acidic, basic, or neutral?
a.) 100 mL of 0.20 M HCl + 20 mL of 0.50 M NaOH Acidic (because there's more of the solution with the lower molarity and that overpowers the base)
b.) 100 mL of 0.20 M HCL + 40 mL of 0.50 M NaOH Neutral (there is enough base to neutralize the acid, despite their different molarities)
c.) 100 mL of 0.20 M HCl + 60 mL of 0.50 M NaOH Basic (if 40 is the neutral point, anything above that as far as the NaOH is concerned should be basic.)
Thursday, November 29, 2012
Unit 4, Lesson 21
A neutralization reaction, also considered a double exchange reaction, occurs when a base is used to render an acid neutral, or when an acid is used to neutralize a base. When an acid and base are mixed, an aqueous, ionic compound (a salt) and H2O (water) are produced. In pure water kept at 25 degrees C, when there are equal amounts of acid and base, there are equal amounts of H+ ions and OH- ions.
There are weak acids and bases, and strong acids and bases. Strong acids and bases dissociate (break apart) completely in water and completely disperse their ions. They are also the most dangerous acids and bases and don't mean good news when they come into contact with skin, your insides, your clothing, etc. Weak acids and bases, however, do not dissociate completely. They're generally safer. Some typical weak acids are vinegar and citric acid, which is found in fruit. Ammonia, a household cleaner, is a weak base (but, like any kind of soap or cleaner, shouldn't be ingested. Not that smart Chem Honors kids need to be reminded of that!)
Problems:
5.) Suppose you mix 1 mol of sulfuric acid, H2SO4, with 1 mol of sodium hydroxide, NaOH. Why does the pH of the solution remain below 7? There are not enough H+ ions in NaOH to neutralize the H+ ions in the sulfuric acid, which has 2 hydrogen. There are also not enough oxygen atoms. Either you need more sodium hydroxide, or a stronger base to neutralize the H2SO4.
8.) What combination of reactants would result in a neutralization reaction with sodium nitrate, NaNO3, as one of the products? (Mg(NO3)2 + NaOH, HNO3 + NaOH, CH3OH + NaOH, HNO3 + NaCl) Combination D, which is HNO3 + NaCl.
There are weak acids and bases, and strong acids and bases. Strong acids and bases dissociate (break apart) completely in water and completely disperse their ions. They are also the most dangerous acids and bases and don't mean good news when they come into contact with skin, your insides, your clothing, etc. Weak acids and bases, however, do not dissociate completely. They're generally safer. Some typical weak acids are vinegar and citric acid, which is found in fruit. Ammonia, a household cleaner, is a weak base (but, like any kind of soap or cleaner, shouldn't be ingested. Not that smart Chem Honors kids need to be reminded of that!)
Problems:
5.) Suppose you mix 1 mol of sulfuric acid, H2SO4, with 1 mol of sodium hydroxide, NaOH. Why does the pH of the solution remain below 7? There are not enough H+ ions in NaOH to neutralize the H+ ions in the sulfuric acid, which has 2 hydrogen. There are also not enough oxygen atoms. Either you need more sodium hydroxide, or a stronger base to neutralize the H2SO4.
8.) What combination of reactants would result in a neutralization reaction with sodium nitrate, NaNO3, as one of the products? (Mg(NO3)2 + NaOH, HNO3 + NaOH, CH3OH + NaOH, HNO3 + NaCl) Combination D, which is HNO3 + NaCl.
Unit 4, Lesson 20
The process of "watering down" an acidic or basic solution is called dilution. It simply entails adding water to an acid or base to, in an acid's case, raise the pH toward 7, or in a base's case, lower the pH toward 7. 7 is considered "neutral" for any substance. Diluting a substance makes it weaker, or less concentrated, since adding water lowers the molarity. When the molarity of an acid or base is lowered, the pH increases by 1. This is because the pH scale is logarithmic, and a tiny change in pH makes for a huge change in concentration. For example, changing an acid from a pH of 3 to a pH of 4 makes that acid 10x less acidic. Changing it to pH 5 is 100x more acidic. pH 6, 1000x more acidic, and so on.
Though diluting an acid or base is meant to make it more neutral, one cannot achieve full neutrality. Rather, they can get very close. An acid can only be diluted to a pH between 6 and 6.9. A base can only be diluted to a pH around 7.1 (or 8, because any pH above 7 is basic).
Problems:
2.) Explain why you can't turn an acid into a base by diluting with water. You can't eliminate the acid completely--you can only neutralize it, because water is neutral. However, if you were diluting with a base, you could change the acid, because the pH would gradually raise until it was high enough to be a base.
4.) How much water do you need to add to 10 mL of a solution of HCl with a pH of 3 to change it to a pH of 6? 999 mL of water.
pH of 3 = .0010 M
pH of 4 = .00010 M (10x less acidic) (+9 mL of water)
pH of 5 = .000010 M (100x less acidic) (+99 mL of water)
pH of 6 = .0000010M (1,000x less acidic) (+999 mL of water)
...I don't know if that's correct. I'm a bit fuzzy on this myself.
Though diluting an acid or base is meant to make it more neutral, one cannot achieve full neutrality. Rather, they can get very close. An acid can only be diluted to a pH between 6 and 6.9. A base can only be diluted to a pH around 7.1 (or 8, because any pH above 7 is basic).
Problems:
2.) Explain why you can't turn an acid into a base by diluting with water. You can't eliminate the acid completely--you can only neutralize it, because water is neutral. However, if you were diluting with a base, you could change the acid, because the pH would gradually raise until it was high enough to be a base.
4.) How much water do you need to add to 10 mL of a solution of HCl with a pH of 3 to change it to a pH of 6? 999 mL of water.
pH of 3 = .0010 M
pH of 4 = .00010 M (10x less acidic) (+9 mL of water)
pH of 5 = .000010 M (100x less acidic) (+99 mL of water)
pH of 6 = .0000010M (1,000x less acidic) (+999 mL of water)
...I don't know if that's correct. I'm a bit fuzzy on this myself.
Sunday, November 25, 2012
Disappearing Spoon- Ch. 8-9
Chapter 8:
Attention to detail plays a humongous role in science. Making sure you have the correct information in an experiment, or while researching, prevents you from having to deal with a bunch of skewed data in the end. Unfortunately, the scientists Pauling and Segre didn't quite grasp this concept. In a feverish race to catch a Nobel Prize, they were doing research in their own fields and working together at Berkeley. Pauling was studying DNA and its ability to carry genetic information. He made a big mistake and observed a dry sample of DNA rather than a wet one. The two had different numbers of helixes, and in studying the dry one, he missed out on his shot at the Nobel Prize. Some students at Cambridge discovered Pauling's mistake and claimed the prize for their own. Segre was among the many who wanted to discover new elements. He took to experimenting with strips of molybdenum, hoping to find some element hidden inside of it. He did: technetium. Technetium is element 43, and was perhaps the most elusive of all the elements in the table. Several claimed they'd discovered it for the "first time", only to be proved wrong.
Chapter 9:
This chapter discussed toxic elements that are present in our everyday lives, and how they can harm us. Sometimes we don't even realize that radioactive, unstable, and in other ways toxic elements are around us. One such element is cadmium. Cadmium was a product of warfare, specifically Japanese warfare. After the battles had been fought, remnants of the toxic element could be found in the water. There were some rice farmers near the Kamioka mines that ate what they harvested and fell sick with mysterious illnesses. These illnesses seemed to be chronic, and it was discovered later that cadmium is toxic when ingested. In spite of this, cadmium is not the most poisonous element--no, those are lead, thallium, and polonium. There are other elements, like the alkali metals, that would literally explode inside someone once they came into contact with any moisture. Chapter 9 also talked about how troublesome kids can be when they get their heads into science. David Hahn, described by Kean as a sixteen year old boy scout, spent a lot of time in his mother's shed playing with something crude. Something he called a nuclear reactor. It was his wish to end the world's hunger for oil by offering them an alternative. His young research didn't go very far; he got stuck doing chore-like work.
Attention to detail plays a humongous role in science. Making sure you have the correct information in an experiment, or while researching, prevents you from having to deal with a bunch of skewed data in the end. Unfortunately, the scientists Pauling and Segre didn't quite grasp this concept. In a feverish race to catch a Nobel Prize, they were doing research in their own fields and working together at Berkeley. Pauling was studying DNA and its ability to carry genetic information. He made a big mistake and observed a dry sample of DNA rather than a wet one. The two had different numbers of helixes, and in studying the dry one, he missed out on his shot at the Nobel Prize. Some students at Cambridge discovered Pauling's mistake and claimed the prize for their own. Segre was among the many who wanted to discover new elements. He took to experimenting with strips of molybdenum, hoping to find some element hidden inside of it. He did: technetium. Technetium is element 43, and was perhaps the most elusive of all the elements in the table. Several claimed they'd discovered it for the "first time", only to be proved wrong.
Chapter 9:
This chapter discussed toxic elements that are present in our everyday lives, and how they can harm us. Sometimes we don't even realize that radioactive, unstable, and in other ways toxic elements are around us. One such element is cadmium. Cadmium was a product of warfare, specifically Japanese warfare. After the battles had been fought, remnants of the toxic element could be found in the water. There were some rice farmers near the Kamioka mines that ate what they harvested and fell sick with mysterious illnesses. These illnesses seemed to be chronic, and it was discovered later that cadmium is toxic when ingested. In spite of this, cadmium is not the most poisonous element--no, those are lead, thallium, and polonium. There are other elements, like the alkali metals, that would literally explode inside someone once they came into contact with any moisture. Chapter 9 also talked about how troublesome kids can be when they get their heads into science. David Hahn, described by Kean as a sixteen year old boy scout, spent a lot of time in his mother's shed playing with something crude. Something he called a nuclear reactor. It was his wish to end the world's hunger for oil by offering them an alternative. His young research didn't go very far; he got stuck doing chore-like work.
Thursday, November 15, 2012
Unit 4, Lesson 19
Suppose you have a solution whose pH you know, but whose concentration of H+ ions and OH- ions you don't know. There's a simple formula you can use to find any of your missing links, and it is as follows:
pH = -log[ H+]
[ H+] = 10^-pH
The first equation is used to find the pH of the substance if the number of hydrogen ions (which is listed in scientific notation) is known. The second, scientists use to find hydrogen ions by taking the pH, making it a negative number, and writing it in scientific notation.
To find OH- ions, know that the product of hydrogen and hydroxide ions is always equivalent to 1 x 10^-14. If you know one value of ions, divide 1 x 10^-14 by it to find the other value.
Problems:
7.) What is the pH of a 2.5 M HCl solution? The pH of this solution is 0, because the decimal is after the 2, not before. Its H+ concentration is 1 x 10^0.
8.) What is the pH of a 0.256 M NaOH solution? 11. The H+ concentration is 1 x 10^-11, the OH- concentration is 1 x 10^-3.
Unit 4, Lessons 17 and 18
Lesson 17:
Substances can be classified as acids, bases, or neutral solutions. Whether or not a solution gets classified as one of those three depends on its pH, which is a measure of the concentration of hydrogen and hydroxide ions. Acids have a very low pH number (anything less than 7). Bases sit on the complete other side of the scale and have pHs above 7. Any solution with a pH of exactly 7 is neutral. Table salt and pure water are neutral; lemon juice is an acid (FUN FACT: so is milk!), and soap is a base. Acids and bases are both very corrosive and sometimes unsafe to handle. How exactly does one tell if a solution is acidic or basic? Through the use of an indicator, a molecular substance that changes colors in acidic and basic environments. There are two common types of indicators: cabbage juice (easily accessible at home) and Universal Indicator (not as easily acquired, but much more accurate).
Problems:
1.) What are some observable properties of acids and bases? Acids are typically sour, if they're safe to eat. Bases, like soap, taste bitter and sometimes foam up in water. Both acids and bases can be corrosive.
2.) What is the pH scale? The pH scale is a colored number line, essentially, that associates different types of solutions with colors to help one determine if they're basic or acidic. Basic solutions are usually in darker greens, blues, and purples on the scale; acids show up as vibrant reds, oranges, and yellows.
Lesson 18:
The laws for identifying basic, neutral, and acidic solutions have changed over time. Most of the laws, though, have always involved the hydrogen and hydroxide ions that pH measures. In a chemical reaction, acids give away one H+ ion, which shows up in the products. The product that has one more H+ ion than before is the starting acid (reactant)'s corresponding base. Oppositely, bases give off OH- ions in their reactions, and the product that receives the base's OH- is its corresponding acid. In these processes, which are defined Arrheniously, Bronsted-Lowry's law comes into play. It states that acidic solutions are proton donors (since H+ ions are simply stray protons) and basic solutions are proton acceptors.
Problems:
2.) How is the Bronsted-Lowry theory of acids similar to the Arrhenius theory? How is it different? These two theories are similar in that they both deal with the identification of solutions as acids/bases through whatever ions are present. They're different in that the Arrhenius theory doesn't explain how solutions without OH- ions in their chemical formulas can be bases, too.
7.) Explain why aqueous washing soda, NaCO3, is a basic solution. It is a basic solution because it has one OH- ion in its composition. (Also, it's a kind of soap, which is also a giveaway).
Substances can be classified as acids, bases, or neutral solutions. Whether or not a solution gets classified as one of those three depends on its pH, which is a measure of the concentration of hydrogen and hydroxide ions. Acids have a very low pH number (anything less than 7). Bases sit on the complete other side of the scale and have pHs above 7. Any solution with a pH of exactly 7 is neutral. Table salt and pure water are neutral; lemon juice is an acid (FUN FACT: so is milk!), and soap is a base. Acids and bases are both very corrosive and sometimes unsafe to handle. How exactly does one tell if a solution is acidic or basic? Through the use of an indicator, a molecular substance that changes colors in acidic and basic environments. There are two common types of indicators: cabbage juice (easily accessible at home) and Universal Indicator (not as easily acquired, but much more accurate).
Problems:
1.) What are some observable properties of acids and bases? Acids are typically sour, if they're safe to eat. Bases, like soap, taste bitter and sometimes foam up in water. Both acids and bases can be corrosive.
2.) What is the pH scale? The pH scale is a colored number line, essentially, that associates different types of solutions with colors to help one determine if they're basic or acidic. Basic solutions are usually in darker greens, blues, and purples on the scale; acids show up as vibrant reds, oranges, and yellows.
Lesson 18:
The laws for identifying basic, neutral, and acidic solutions have changed over time. Most of the laws, though, have always involved the hydrogen and hydroxide ions that pH measures. In a chemical reaction, acids give away one H+ ion, which shows up in the products. The product that has one more H+ ion than before is the starting acid (reactant)'s corresponding base. Oppositely, bases give off OH- ions in their reactions, and the product that receives the base's OH- is its corresponding acid. In these processes, which are defined Arrheniously, Bronsted-Lowry's law comes into play. It states that acidic solutions are proton donors (since H+ ions are simply stray protons) and basic solutions are proton acceptors.
Problems:
2.) How is the Bronsted-Lowry theory of acids similar to the Arrhenius theory? How is it different? These two theories are similar in that they both deal with the identification of solutions as acids/bases through whatever ions are present. They're different in that the Arrhenius theory doesn't explain how solutions without OH- ions in their chemical formulas can be bases, too.
7.) Explain why aqueous washing soda, NaCO3, is a basic solution. It is a basic solution because it has one OH- ion in its composition. (Also, it's a kind of soap, which is also a giveaway).
Monday, November 12, 2012
Disappearing Spoon, Ch. 5-7
Chapter five taught me that The Disappearing Spoon is an excellent choice of reading material for long car rides between states. Kean talked at length about Fritz Haber and his ground-breaking chemical contributions to German warfare. I found myself a bit resentful toward Haber when I read how he treated his wife and his friends. I suppose that it really is possible to devote every speck of your soul to science. Fritz's specialty when tinkering with his chemicals was creating deadly gas weapons that could wipe out entire armies of enemy men. His formulas were potent, containing elements of chlorine, bromine, and nitrogen. Ironically, this man of scientific genius got what was coming to him in throwing away his personal relationships. He ended up being captured for being Jewish by Nazis, and a watered-down version of one of his gases was used in concentration camps to eradicate other Jews. Right in the feel-bads, huh? I have to say, one of my favorite elements of this book so far is the heavy amount of German history in it.
In chapter six, the material focused on how the last few spots in Mendeleev's periodic table were filled. It's tragic to look at dear promethium, with its dark and mysterious name, and know that it wasn't good for much but taking a seat among other relatively useless elements. As I (and Kean) mentioned before, Mendeleev's table underwent tons of changes after the time of its creation. Everything from rearranging the order of Mendeleev's elements, to changing the degree at which the table sits, happened. A man named Henry Moseley helped sort out some crucial kinks in the table, like switching elements that didn't make sense. He was the one to propose that elements should be placed in order of increasing atomic number, along with mass. After Moseley joined the army and was killed in action, a sequence of finding new elements for the table began, and after that, the neutron was discovered and used to explain isotopes. Scientists and the public now understood that two elements could have different weights, but still keep their identity, which kept some people from throwing elements out of the table. The rest of the chapter sort of went on about the Manhattan Project and the team's unorthodox experimentation. Kean's tone seemed interested (as it always has, up to this point) in the method of throwing random numbers into a sequence, calculating, and hoping a good product would emerge. This kind of testing, I realized, is sort of like the scientific method that we're taught today: observe, hypothesize, conduct the experiment. If something doesn't turn out right, change a variable and do it all again.
In chapter seven, Kean frantically went on about Berkeley and its feverish endeavor to find as many elements for the table as possible. Of course, they couldn't have all the elements out there to themselves, so other countries outside the U.S., like Russia, were quick to try their hand at the synthesizing process. When someone other than Berkeley came up with a new element, the lab checked their work. They didn't take kindly to seeing correct data different than theirs. (Like a kid who thinks they always have to be right!) Naming elements proved, challenging, too, because some names were either dry or offensive to the public. Believe it or not, communism in Russia affected the scientists that were trying to fill the table. Joseph Stalin and his followers were among perhaps the most stubborn of men and didn't believe that what the scientists were trying was legitimate. He thought it traitorous to his socialist government and tried to have the process shut down, executing physicists and chemists alike or forcing them to work in unimaginable conditions. So many people tried to get in on naming/synthesizing new elements that the endeavor became more of a game than a race to fill the table, and when people started fighting over who could earn a square on the periodic table, a high-and-mighty, official team of people had to sift through all the B.S. and decide.
Friday, November 9, 2012
Unit 4, Lessons 15 and 16
Lesson 15:
One can create a solution with a specific molarity by using the molar mass of the solid. If the amount of solid you have is given, you can find out how many moles of that substance are needed with a chart (which we've already gone over) and the molar mass. If the concentration or the volume is given, you can substitute it into the molarity concentration to find the other value you need. For example, if you need .01 L of a 0.5 M solution, you would need 0.5 grams of your solute. How did I get this? Plug the known values into the molarity equation to get 0.5 = n / 0.01. Multiply each side by 0.01 to get n = 0.005 moles of solute. Convert moles to grams of solute by using the molar mass of, in this case, NaBr, to get 0.515 g. That rounds to 0.5!
Problems:
1.) Explain how you would create a solution of sucrose with a molarity of 0.25. I think I would first need to know the volume of solution I am making. Then, I would multiply that volume by the molarity, 0.25 M, to get my # of moles. I would convert the moles to grams and that would tell me how much sucrose I need to make this solution.
6.) How many grams of fructose, C6H12O6, are in 1 L of soft drink if the molarity of fructose in the drink is 0.75 M? First off, the molar mass of fructose is about 180 g. In the equation 0.75 M = n / 1, I find that this solution has 0.75 moles of fructose. Converting moles to grams, I multiply 0.75 by 180 and get 135 grams of fructose in this soft drink.
Lesson 16:
We really didn't have many notes for this lesson, since we really just perfected our skills from 15. The gist of lesson 16 is that the type of substance being dissolved in a solution affects the whole solution's mass. The mass of one mole of one substance could be very different than the mass of one mole of another substance.
Problems:
1.) Explain how you might use mass to determine if a sample of water is contaminated. You might be able to figure out if the water is contaminated by finding its density/mass and then comparing the sample to a sample of "normal" water. If the results are different, one sample of water probably has some extra substances in it, like minerals or toxins.
3.) Explain why 0.10 M CuCl2 has a greater density than 0.10 M KCl. The densities are different because the solutions contain two different compounds, and CuCl2 has a greater molar mass than KCl.
One can create a solution with a specific molarity by using the molar mass of the solid. If the amount of solid you have is given, you can find out how many moles of that substance are needed with a chart (which we've already gone over) and the molar mass. If the concentration or the volume is given, you can substitute it into the molarity concentration to find the other value you need. For example, if you need .01 L of a 0.5 M solution, you would need 0.5 grams of your solute. How did I get this? Plug the known values into the molarity equation to get 0.5 = n / 0.01. Multiply each side by 0.01 to get n = 0.005 moles of solute. Convert moles to grams of solute by using the molar mass of, in this case, NaBr, to get 0.515 g. That rounds to 0.5!
Problems:
1.) Explain how you would create a solution of sucrose with a molarity of 0.25. I think I would first need to know the volume of solution I am making. Then, I would multiply that volume by the molarity, 0.25 M, to get my # of moles. I would convert the moles to grams and that would tell me how much sucrose I need to make this solution.
6.) How many grams of fructose, C6H12O6, are in 1 L of soft drink if the molarity of fructose in the drink is 0.75 M? First off, the molar mass of fructose is about 180 g. In the equation 0.75 M = n / 1, I find that this solution has 0.75 moles of fructose. Converting moles to grams, I multiply 0.75 by 180 and get 135 grams of fructose in this soft drink.
Lesson 16:
We really didn't have many notes for this lesson, since we really just perfected our skills from 15. The gist of lesson 16 is that the type of substance being dissolved in a solution affects the whole solution's mass. The mass of one mole of one substance could be very different than the mass of one mole of another substance.
Problems:
1.) Explain how you might use mass to determine if a sample of water is contaminated. You might be able to figure out if the water is contaminated by finding its density/mass and then comparing the sample to a sample of "normal" water. If the results are different, one sample of water probably has some extra substances in it, like minerals or toxins.
3.) Explain why 0.10 M CuCl2 has a greater density than 0.10 M KCl. The densities are different because the solutions contain two different compounds, and CuCl2 has a greater molar mass than KCl.
Unit 4, Lessons 13 and 14
Lesson 13:
A solution is a mixture of two or more substances that is uniform throughout. You can keep track of what you're putting into a solution by measuring the number of particles. That said, we call the total number of particles the concentration of the solution, which is simply how densely saturated a solution is with something. (Example: how much hot chocolate powder is in a mug of hot water. More powder= higher concentration, more chocolateness. Less powder = lower concentration, less chocolateness. Ew.) Another, more science-y word for concentration is molarity, represented by the following equation:
A solution is a mixture of two or more substances that is uniform throughout. You can keep track of what you're putting into a solution by measuring the number of particles. That said, we call the total number of particles the concentration of the solution, which is simply how densely saturated a solution is with something. (Example: how much hot chocolate powder is in a mug of hot water. More powder= higher concentration, more chocolateness. Less powder = lower concentration, less chocolateness. Ew.) Another, more science-y word for concentration is molarity, represented by the following equation:
Molarity (M) = number of moles (n) / Volume (L)
Problems:
1.) What does it mean when a solution is "uniform throughout"? This means that the solute. Has been thoroughly dissolved in a solvent and there are no random particles or "floaties" in the liquid.
5.) Put these three solutions in order of increasing molarity.
A.) 4.0 mol per 8.0 L: molarity is 0.5 mol/L
B.) 6.0 mol per 6.0 L: molarity is 1 mol/L
C.) 1.0 mol per10 L: molarity is 0.1 mol/L
Order: C, A, B.
1.) What does it mean when a solution is "uniform throughout"? This means that the solute. Has been thoroughly dissolved in a solvent and there are no random particles or "floaties" in the liquid.
5.) Put these three solutions in order of increasing molarity.
A.) 4.0 mol per 8.0 L: molarity is 0.5 mol/L
B.) 6.0 mol per 6.0 L: molarity is 1 mol/L
C.) 1.0 mol per10 L: molarity is 0.1 mol/L
Order: C, A, B.
Lesson 14:
In this lesson, we learned the relation of concentration to volume. The concentration does not change if the volume of the solution changes. If a solute is dissolved thoroughly and evenly in the solvent, the number of particles, or the molarity, should not change. Because of this, the equation mentioned in lesson 13 can be used to find molarity, volumes, and the moles in just about any solution.
Problems:
2.) How can you figure out how many moles of solute you have in a solution with a specific concentration? In the equation molarity = moles / volume, finding the number of moles requires multiplying both sides by the volume.
5.) Glucose and sucrose are two different types of sugar. Consider these aqueous solutions: 1.0 L of 1.0 M C6H12O6 (glucose), 1.0 L of 1.0 M C12H22O11 (sucrose), 500mL of 1.0 M C12H22O11 (sucrose):
A.) Which solution has the most molecules? Explain. The glucose solution, because it has the lowest molar mass for the given volume of solvent.
B.) Which solution is most concentrated? Explain. The glucose solution, because it has more molecules for a given volume and is more saturated with glucose.
C.) Which solution has the most mass? Explain. The first sucrose solution has the most mass, because it has a larger volume than the last sucrose solution and sucrose has a larger molar mass than glucose.
Problems:
2.) How can you figure out how many moles of solute you have in a solution with a specific concentration? In the equation molarity = moles / volume, finding the number of moles requires multiplying both sides by the volume.
5.) Glucose and sucrose are two different types of sugar. Consider these aqueous solutions: 1.0 L of 1.0 M C6H12O6 (glucose), 1.0 L of 1.0 M C12H22O11 (sucrose), 500mL of 1.0 M C12H22O11 (sucrose):
A.) Which solution has the most molecules? Explain. The glucose solution, because it has the lowest molar mass for the given volume of solvent.
B.) Which solution is most concentrated? Explain. The glucose solution, because it has more molecules for a given volume and is more saturated with glucose.
C.) Which solution has the most mass? Explain. The first sucrose solution has the most mass, because it has a larger volume than the last sucrose solution and sucrose has a larger molar mass than glucose.
Sunday, November 4, 2012
Disappearing Spoon, Ch.3-4
Reading about a man who toiled with arsenic is, to say the least, a bit disturbing. Arsenic has an explosive love-hate relationship with just about anything, it seems, even Robert Bunsen. As anyone well knows, arsenic is deadly stuff. Robert Bunsen loved messing with elements and, like most chemists would be, enjoyed finding new ones. He invented the first spectroscope a tool that identifies unknown substances by color. It resembles a cowbell, almost. A page or two into the chapter, Kean switches gears and starts talking about the periodic table again, this time disputing who made it. Great minds think alike, and when Mendeleev first began piecing together the structure that we know today, many others were doing the same. Mendeleev is given credit for the periodic table even though he did not discover all the elements needed to complete it, like the lanthanides.
In chapter 4, a reader learns just how silly humanity can be. That might seem cynical, but the reality that humans like to make [expletive] up is quite comical. When sticking their heads together to try and find out where elements hailed from, or if they could be forged, some pretty ridiculous theories arose. A giant comet landing on Earth and wiping out the dinosaurs was proposed as an explanation, most likely for the amount of heat and energy that resulted upon impact. Since those phenomena happen patterns an ungodly amount of years apart, it's possible that new elements could result from whatever comes to destroy the human race. Perhaps UFOs could give us our next set of tinker toys! Most know that elements like gold can only be forged in celestial explosions, a.k.a. supernovas, and don't appear on earth by human means. Supernovas are logically the producers of other elements, just like we're starchildren made of cosmic dust.
In chapter 4, a reader learns just how silly humanity can be. That might seem cynical, but the reality that humans like to make [expletive] up is quite comical. When sticking their heads together to try and find out where elements hailed from, or if they could be forged, some pretty ridiculous theories arose. A giant comet landing on Earth and wiping out the dinosaurs was proposed as an explanation, most likely for the amount of heat and energy that resulted upon impact. Since those phenomena happen patterns an ungodly amount of years apart, it's possible that new elements could result from whatever comes to destroy the human race. Perhaps UFOs could give us our next set of tinker toys! Most know that elements like gold can only be forged in celestial explosions, a.k.a. supernovas, and don't appear on earth by human means. Supernovas are logically the producers of other elements, just like we're starchildren made of cosmic dust.
Disappearing Spoon: Intro, Ch.1-2
The Disappearing Spoon begins by likening the periodic table to some kind of ancient treasure. A holy grail of ordinary people and scientists. Though Sam Kean chooses to focus on the element mercury throughout the introduction, he always ties his points back to a central idea, that the periodic table stands as the basic building block, as atoms do, for all scientific play. He begins his story by retelling for the reader a childhood memory of catching strep throat and having his mouth full of mercury thermometers. Living in an age where it appears taboo to handle the stuff, I was eager to read about his early experiences with mercury. By describing the silvery metal as though it's living, breathing, and existing as humans do, Kean creates an atmosphere that clearly lays out the importance--and interest--of the periodic table.
Like fat and happy kings on thrones, the elements live in a castle called the periodic table. The only reference to this analogy is in the beginning of chapter 1 (which, might I add, was painfully tedious to read). While Kean doesn't go too in depth in explaining why the elements situate themselves how they do, he does describe how the castle would crumble if one was removed from its spot. The chapter talks about the properties of each part of the periodic table, like how alkali metals react easily and quickly with halogens. Kean throws in some nifty scientific history, sarcastically spinning the tales of under-appreciated chemists from Germany.
If ever someone has tried to read a really long word and gotten discouraged enough to shut the book, it happened in chapter two, with the tongue-twister that is the tobacco mosaic virus. Its word is just that--a mosaic. For only the most artful of tongues. Kean seems flirtatious with carbon in this chapter, diving into its properties in forming amino acids. He takes a breath and tells the reader what an amino acid is, as well. (This book might as well be a Chemistry lesson; Darcy, I can see where you found it dry.) The chapter ends with a sweet little description of silicon and germanium integration in technology.
Like fat and happy kings on thrones, the elements live in a castle called the periodic table. The only reference to this analogy is in the beginning of chapter 1 (which, might I add, was painfully tedious to read). While Kean doesn't go too in depth in explaining why the elements situate themselves how they do, he does describe how the castle would crumble if one was removed from its spot. The chapter talks about the properties of each part of the periodic table, like how alkali metals react easily and quickly with halogens. Kean throws in some nifty scientific history, sarcastically spinning the tales of under-appreciated chemists from Germany.
If ever someone has tried to read a really long word and gotten discouraged enough to shut the book, it happened in chapter two, with the tongue-twister that is the tobacco mosaic virus. Its word is just that--a mosaic. For only the most artful of tongues. Kean seems flirtatious with carbon in this chapter, diving into its properties in forming amino acids. He takes a breath and tells the reader what an amino acid is, as well. (This book might as well be a Chemistry lesson; Darcy, I can see where you found it dry.) The chapter ends with a sweet little description of silicon and germanium integration in technology.
Thursday, November 1, 2012
Unit 4, Lessons 11 and 12
Lesson 11:
Like I've already touched on, you can find out how many moles of molecules are in a sample or how many grams that sample weighs by the use of these two tables:
x moles (sample) | y grams
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Sometimes, the unit isn't grams, but milligrams, or perhaps micrograms. Some simple conversions can help with that inconvenience. For example, 1000 milligrams = 1 gram. It's very important to have all your masses in the same units before you try to find moles or grams.
Problems:
2.) Why might a 200 mg tablet of aspirin not have the same effect as a 200 mg tablet of ibuprofen? They are two different medications and their dosages may be different depending on how old the person taking the medication is.
5.) Which has more moles of oxygen atoms, 153 g of BaO or 169 g of BaO2? BaO2 has more moles of oxygen atoms because the number of moles is always equivalent to the value of the subscript. Since there are two atoms of oxygen in BaO2 vs. only one atom in BaO, BaO2 has two moles of oxygen.
Lesson 12:
This lesson talked about how the LD50 doesn't take into consideration the long-term effects of certain toxins. If a substance's molar mass is large, it takes less of that substance to achieve a lethal does. If it has a small mass, it takes more of it. Even if it takes less to poison one with a substance, it doesn't necessarily negate the fact that there can be pretty nasty side effects. For example, an easily-achieved overdose, if it fails, can leave one with severe liver damage, ulcers, and perhaps even neurological damage.
Problems:
2.) What evidence shows that it would be difficult to exceed the lethal dose of aspartame? The LD50 for aspartame is 10 g/kg. Depending on how much aspartame is used in a can of soda, or any other artificially-sweetened drink, it takes a long time to drink a ton of diet soda. You will not achieve a lethal dose of aspartame in a short time.
4.) The LD50 for saccharin, C7H5NO3S, is 14.2 g/kg. If you have 1 mole of aspartame and 1 mole of saccharin, which would be more toxic? Show your work. The LD50 for aspartame is 10g/kg, which is less than the LD50 for saccharin. It's easy to look at those two numbers and decide that aspartame is the more toxic of the two, because it takes less of it to both sweeten a drink, or poison someone.
Like I've already touched on, you can find out how many moles of molecules are in a sample or how many grams that sample weighs by the use of these two tables:
x grams (sample) | 1 mole
------------------------------------------------------ = # of moles
| y grams (molar mass)
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Sometimes, the unit isn't grams, but milligrams, or perhaps micrograms. Some simple conversions can help with that inconvenience. For example, 1000 milligrams = 1 gram. It's very important to have all your masses in the same units before you try to find moles or grams.
Problems:
2.) Why might a 200 mg tablet of aspirin not have the same effect as a 200 mg tablet of ibuprofen? They are two different medications and their dosages may be different depending on how old the person taking the medication is.
5.) Which has more moles of oxygen atoms, 153 g of BaO or 169 g of BaO2? BaO2 has more moles of oxygen atoms because the number of moles is always equivalent to the value of the subscript. Since there are two atoms of oxygen in BaO2 vs. only one atom in BaO, BaO2 has two moles of oxygen.
Lesson 12:
This lesson talked about how the LD50 doesn't take into consideration the long-term effects of certain toxins. If a substance's molar mass is large, it takes less of that substance to achieve a lethal does. If it has a small mass, it takes more of it. Even if it takes less to poison one with a substance, it doesn't necessarily negate the fact that there can be pretty nasty side effects. For example, an easily-achieved overdose, if it fails, can leave one with severe liver damage, ulcers, and perhaps even neurological damage.
Problems:
2.) What evidence shows that it would be difficult to exceed the lethal dose of aspartame? The LD50 for aspartame is 10 g/kg. Depending on how much aspartame is used in a can of soda, or any other artificially-sweetened drink, it takes a long time to drink a ton of diet soda. You will not achieve a lethal dose of aspartame in a short time.
4.) The LD50 for saccharin, C7H5NO3S, is 14.2 g/kg. If you have 1 mole of aspartame and 1 mole of saccharin, which would be more toxic? Show your work. The LD50 for aspartame is 10g/kg, which is less than the LD50 for saccharin. It's easy to look at those two numbers and decide that aspartame is the more toxic of the two, because it takes less of it to both sweeten a drink, or poison someone.
Unit 4, Lessons 9 and 10
Lesson 9:
Scientists use scientific notation to express numbers that are very big or very small. Correct scientific notation has only 1 digit before the decimal point! We've studied the use of scientific notation to express how many molecules are in a test sample. Once again, we looked at moles. One mole, 602 sextillion, is written in scientific notation as 6.022 x 10^23. The term "molar mass" refers to how much of a substance is needed to achieve 1 mole of molecules. The molar masses for all the known elements are the same as the atomic masses on the periodic table. Molar mass helps scientists convert between moles of atoms and grams of atoms. That's where the two tables I mentioned in lesson 7 come into play.
Problems:
4.) Give the molar mass for these elements:
A.) nitrogen, N - 14.0 g
B.) neon, Ne - 20.2 g
C.) chlorine, Cl - 35.5 g
D.) copper, Cu - 63.5 g
6.) Which contains more atoms?
A.) 12 g of hydrogen, H, or 12 g of carbon, C? 12 g of hydrogen. Hydrogen has the smaller molar mass.
B.) 27 g of aluminum, Al, or 27 g of iron, Fe? 27 g of aluminum. Aluminum has the smaller molar mass.
C.) 40 g of calcium, Ca, or 40 g of sodium, Na? 40 g of sodium. Sodium has the smaller molar mass.
D.) 40 g of calcium, Ca, or 40 g of zinc, Zn? 40 g of calcium. Calcium has the smaller molar mass.
E.) 10 g of lithium, Li, or 100 g of lead, Pb? 100 g of Pb, because it has the larger sample size.
Lesson 10:
Because individual atoms cannot be counted easily by themselves, scientists compare moles of substances rather than masses of substances. If one was given 50 moles of one element and 50 moles of another, their molar masses are significant, but only in telling which element would be lighter. Then, it's up to us to decide which sample is larger based off of how many more/less atoms it takes to make an equal sample. If given a compound, where the molar mass isn't clear but rather a bunch of molar masses thrown together, one must add the masses of each element in the compound, multiply by the subscripts (if there are any) and add all the masses together to find the compound's whole mass.
Problems:
5.) Which has more moles of metal atoms?
A.) 10.0 g of calcium, Ca, or 10.0 g of calcium chloride, CaCl2? Calcium chloride, CaCl2
B.) 5.0 g of sodium chloride, NaCl, or 5.0 g of sodium fluoride, NaF? Sodium fluoride, NaF
C.) 2.0 g of iron oxide, FeO, or 2.0 g of iron sulfide, FeS? Iron oxide, FeO
7.) What is the mass of 5 mol of iron (III) oxide, Fe2O3?
Mass of iron: 55.8, x2 = 111.6 g
Mass of oxygen: 15.9, x3= 47.7 g
111.6 g + 47.7 g = 159.3 g <--- ONE MOLE
159.3 g x 5 moles = 796.5 g
Scientists use scientific notation to express numbers that are very big or very small. Correct scientific notation has only 1 digit before the decimal point! We've studied the use of scientific notation to express how many molecules are in a test sample. Once again, we looked at moles. One mole, 602 sextillion, is written in scientific notation as 6.022 x 10^23. The term "molar mass" refers to how much of a substance is needed to achieve 1 mole of molecules. The molar masses for all the known elements are the same as the atomic masses on the periodic table. Molar mass helps scientists convert between moles of atoms and grams of atoms. That's where the two tables I mentioned in lesson 7 come into play.
Problems:
4.) Give the molar mass for these elements:
A.) nitrogen, N - 14.0 g
B.) neon, Ne - 20.2 g
C.) chlorine, Cl - 35.5 g
D.) copper, Cu - 63.5 g
6.) Which contains more atoms?
A.) 12 g of hydrogen, H, or 12 g of carbon, C? 12 g of hydrogen. Hydrogen has the smaller molar mass.
B.) 27 g of aluminum, Al, or 27 g of iron, Fe? 27 g of aluminum. Aluminum has the smaller molar mass.
C.) 40 g of calcium, Ca, or 40 g of sodium, Na? 40 g of sodium. Sodium has the smaller molar mass.
D.) 40 g of calcium, Ca, or 40 g of zinc, Zn? 40 g of calcium. Calcium has the smaller molar mass.
E.) 10 g of lithium, Li, or 100 g of lead, Pb? 100 g of Pb, because it has the larger sample size.
Lesson 10:
Because individual atoms cannot be counted easily by themselves, scientists compare moles of substances rather than masses of substances. If one was given 50 moles of one element and 50 moles of another, their molar masses are significant, but only in telling which element would be lighter. Then, it's up to us to decide which sample is larger based off of how many more/less atoms it takes to make an equal sample. If given a compound, where the molar mass isn't clear but rather a bunch of molar masses thrown together, one must add the masses of each element in the compound, multiply by the subscripts (if there are any) and add all the masses together to find the compound's whole mass.
Problems:
5.) Which has more moles of metal atoms?
A.) 10.0 g of calcium, Ca, or 10.0 g of calcium chloride, CaCl2? Calcium chloride, CaCl2
B.) 5.0 g of sodium chloride, NaCl, or 5.0 g of sodium fluoride, NaF? Sodium fluoride, NaF
C.) 2.0 g of iron oxide, FeO, or 2.0 g of iron sulfide, FeS? Iron oxide, FeO
7.) What is the mass of 5 mol of iron (III) oxide, Fe2O3?
Mass of iron: 55.8, x2 = 111.6 g
Mass of oxygen: 15.9, x3= 47.7 g
111.6 g + 47.7 g = 159.3 g <--- ONE MOLE
159.3 g x 5 moles = 796.5 g
Unit 4, Lessons 7 and 8
Lesson 7:
The lethal dose of a substance, also referred to as its LD50, is the amount of substance that it takes to kill 50% of test specimens. All substances have their own LD50, and that number corresponds to kilograms, which means that the amount it takes for a toxin to be very harmful might be more or less. As LD50 increases, so does the amount needed, and vice versa. The truth is, everything on Earth is a toxin, even water and sugar. However, in moderation, some substances, such as vitamins, can be therapeutic and helpful to the body's processes.
Problems:
4.) Ethanol is grain alcohol. The LD50 for ethanol is 7060 mg/kg (rat, oral).
A.) How many milligrams of ethanol would be lethal to a 132 lb adult?
B.) How many glasses containing 13,000 mg of ethanol would be lethal to a 22 lb child?
132 lbs. | 1 kg | 1510 mg
-------------------------- = 90,600 mg would be lethal
2.2 lbs. | 1 kg
Lesson 8:
We've already discussed the mole, and know that 602 sextillion atoms = 1 mole. The mole is just a fancy unit used to measure incredibly large amounts of small objects. One can find how many moles of a substance are present in a sample if they have the molar mass (in grams) of the substance, and the amount of grams of sample that they have. It works the other way around, as well, as illustrated here:
x moles (sample) | y grams
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Scientists weigh large amounts of small objects using mass and basic operations because it isn't possible to count atoms individually. If they are oh-so-curious scientists who want to find out how off their results are, they find percent error, represented by this formula:
The lethal dose of a substance, also referred to as its LD50, is the amount of substance that it takes to kill 50% of test specimens. All substances have their own LD50, and that number corresponds to kilograms, which means that the amount it takes for a toxin to be very harmful might be more or less. As LD50 increases, so does the amount needed, and vice versa. The truth is, everything on Earth is a toxin, even water and sugar. However, in moderation, some substances, such as vitamins, can be therapeutic and helpful to the body's processes.
Problems:
4.) Ethanol is grain alcohol. The LD50 for ethanol is 7060 mg/kg (rat, oral).
A.) How many milligrams of ethanol would be lethal to a 132 lb adult?
132 lbs. | 1 kg | 7060 mg
-------------------------- = 423, 600 mg would be lethal
2.2 lbs. | 1 kg
22 lbs. | 1 kg | 7060 mg
---------------------------- = 70,600 mg
| 2.2 lbs. | 1 kg
70,600 mg / 13,000 mg = 5.43, or about 5 glasses.
5.) The LD50 for Vitamin A is 1510 mg/kg (rat, oral).
A.) How many mg of vitamin A would be lethal to a 132 lb adult?
-------------------------- = 90,600 mg would be lethal
2.2 lbs. | 1 kg
B.) How many vitamin tablets containing 0.40 mg of vitamin A would be lethal to an adult?
90,600 mg / 0.40 mg = 226, 500 tablets
We've already discussed the mole, and know that 602 sextillion atoms = 1 mole. The mole is just a fancy unit used to measure incredibly large amounts of small objects. One can find how many moles of a substance are present in a sample if they have the molar mass (in grams) of the substance, and the amount of grams of sample that they have. It works the other way around, as well, as illustrated here:
x grams (sample) | 1 mole
------------------------------------------------------ = # of moles
| y grams (molar mass)
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Scientists weigh large amounts of small objects using mass and basic operations because it isn't possible to count atoms individually. If they are oh-so-curious scientists who want to find out how off their results are, they find percent error, represented by this formula:
estimated value - actual value
---------------------------------------------- x 100
actual value
Problems:
8.) What is the mass, in grams, of one copper atom? About 64 g if you rounded, 63.54 if you didn't.
10.) Suppose you have 50 grams of copper and 50 grams of gold. Which of these has more atoms? Explain. Since the mass of one copper atom is roughly 64 and the mass of a gold atom is about 170, a 50 g sample of copper has more atoms. Since the samples are equal in size, it takes more, lighter copper atoms to equal as many gold atoms.
Thursday, October 25, 2012
Unit 4, Lessons 5 and 6
Lesson 5:
For a chemical equation to demonstrate a chemical reaction that's actually possible, it must represent a true mathematical relationship between products and reactants. Simply put, there must be an equal number of atoms on each side of the equation. This ties into the law of conservation of mass and that of matter. "True mathematical relationship" is synonymous with "balanced." You can balance an equation by adding coefficients, and coefficients only. Not the little numbers at the bottom, subscripts. Coefficients let scientists know how many molecules or single atoms of a substance there are in an equation. They're measuring tools!
Problems:
1.) Why do chemical equations need to be balanced? Chemical equations that aren't balanced make for reactions that either don't work properly or don't happen at all. When they are balanced, the reactions are easier to control, and typically give one their desired result!
2.) How are subscripts and coefficients different from one another in chemical equations? If there is a substance with an atom that has a subscript, that tiny number only applies to the element that it hugs. The coefficients, however, must be distributed, and thus multiply everything in a compound.
Lesson 6:
Chemical reactions can be classified to a degree further than just "chemical" or "physical". When one looks at a chemical equation, they might notice that some elements or molecules switch places in the products. The new types of classification we learned in Lesson 6 are as follows:
For a chemical equation to demonstrate a chemical reaction that's actually possible, it must represent a true mathematical relationship between products and reactants. Simply put, there must be an equal number of atoms on each side of the equation. This ties into the law of conservation of mass and that of matter. "True mathematical relationship" is synonymous with "balanced." You can balance an equation by adding coefficients, and coefficients only. Not the little numbers at the bottom, subscripts. Coefficients let scientists know how many molecules or single atoms of a substance there are in an equation. They're measuring tools!
Problems:
1.) Why do chemical equations need to be balanced? Chemical equations that aren't balanced make for reactions that either don't work properly or don't happen at all. When they are balanced, the reactions are easier to control, and typically give one their desired result!
2.) How are subscripts and coefficients different from one another in chemical equations? If there is a substance with an atom that has a subscript, that tiny number only applies to the element that it hugs. The coefficients, however, must be distributed, and thus multiply everything in a compound.
Lesson 6:
Chemical reactions can be classified to a degree further than just "chemical" or "physical". When one looks at a chemical equation, they might notice that some elements or molecules switch places in the products. The new types of classification we learned in Lesson 6 are as follows:
Combination: A + B --> AB
Single exchange: A + BC --> AC +B
Double exchange: AB + CD --> AD + CB
Decomposition: AB --> A + B
In combination reactions, reactants combine and form one single product.
In single exchange reactions, reactants combine and one factor from either the first compound or the second switches to create two different products.
In double exchange reactions, two factors, one from both compounds, switch places and make two different products.
In decomposition reactions, an already existing substance breaks apart into its components.
Problems:
4.) List four molecules and four ionic compounds from the reactions in exercise 3.
MOLECULES IONIC COMPOUNDS
HNO3(aq) MgBr2(s)
Cl2(g) NaOH(aq)
C2H4(g) NaNO3(aq)
Br2(s) MgCl2(s)
6.) Solid lithium reacts with aqueous hydrochloric acid to produce hydrogen gas and aqueous lithium chloride: 2Li(s) + 2HCl(aq) --> H2(g) + 2LiCl
^ There are 2 lithium atoms, 2 hydrogen atoms, and 2 chlorine atoms on both sides
Unit 4, Lessons 3 and 4
Lesson 3:
Although the interactions between substances are considered chemical reactions, the changes that the substances go through can be either physical or chemical. A physical change implies that the products (what happens after two or more factors are combined) can be altered in order to regain the reactants. A bowl of trail mix is a good example; you can throw together some pretzels, some cracker chips, some raisins (but who likes raisins in their trail mix anyway?), and some M&Ms in a bowl and then pick out each individual food afterward. A chemical change, on the other hand, can't be so easily reversed. If you mix together eggs, oil, cake mix, and throw that sucker in the oven, you most certainly won't get eggs, oil, and cake mix when you take it out. All the ingredients combine to form a new substance with new (and in this case, delicious) properties.
Problems:
2.) Explain how dissolving can be described as either a physical change or a chemical change. Dissolving is a physical change because a solid changes forms and seems to disappear in a liquid. The liquid can be boiled and the solid will be left behind, such as in the case of salt water. However, also using salt water as an example, sodium and chlorine atoms break apart in water and conduct electricity. Technically, this is the product, which has new properties. Solid salt doesn't conduct electricity.
6.) Classify the following two changes as physical or chemical. Explain your reasoning.
A.) CaCO3(s) + H2SO4(aq) --> CaSO4(aq) + CO2(g) + H20(l) Chemical change, because the products are both different substances and in different phases than the reactants.
B.) NaCl(s) --> NaCl(l) This is just a physical change. The product still has its identity; it is still salt, but it's in liquid form. Now it's salt water.
Lesson 4:
The law of conservation of mass states that, in a chemical reaction, or any action for that matter, mass cannot be created or destroyed. It can, however, go somewhere else. In a chemical equation, the mass of the products is the same as the reactants, even if one of the products is a gas, unless the gas is trapped in a sealed-off container. The mass does not change, regardless of the phase change or the factors being combined, because all atoms are accounted for.
Problems:
2.) Explain how the law of conservation of mass applies to garbage. The law of conservation of mass applies to garbage in that garbage sits in landfills for years, and only some of it biodegrades. What doesn't biodegrade still has matter--and mass, because it exists. We recycle that garbage by taking it and making it into usable products, like bottles, recycled paper, whatever have you. The mass of the garbage is not lost, but it changes forms.
7.) What would you have to do to prove that matter is conserved when a piece of paper is burned? The paper would have to be burned in sealed-off container, such as a glass box or something of that sort. That way, once the paper is burned, both its ashes and any gas released from the burning process is still present. Just find out the mass of the box with a scale.
Although the interactions between substances are considered chemical reactions, the changes that the substances go through can be either physical or chemical. A physical change implies that the products (what happens after two or more factors are combined) can be altered in order to regain the reactants. A bowl of trail mix is a good example; you can throw together some pretzels, some cracker chips, some raisins (but who likes raisins in their trail mix anyway?), and some M&Ms in a bowl and then pick out each individual food afterward. A chemical change, on the other hand, can't be so easily reversed. If you mix together eggs, oil, cake mix, and throw that sucker in the oven, you most certainly won't get eggs, oil, and cake mix when you take it out. All the ingredients combine to form a new substance with new (and in this case, delicious) properties.
Problems:
2.) Explain how dissolving can be described as either a physical change or a chemical change. Dissolving is a physical change because a solid changes forms and seems to disappear in a liquid. The liquid can be boiled and the solid will be left behind, such as in the case of salt water. However, also using salt water as an example, sodium and chlorine atoms break apart in water and conduct electricity. Technically, this is the product, which has new properties. Solid salt doesn't conduct electricity.
6.) Classify the following two changes as physical or chemical. Explain your reasoning.
A.) CaCO3(s) + H2SO4(aq) --> CaSO4(aq) + CO2(g) + H20(l) Chemical change, because the products are both different substances and in different phases than the reactants.
B.) NaCl(s) --> NaCl(l) This is just a physical change. The product still has its identity; it is still salt, but it's in liquid form. Now it's salt water.
Lesson 4:
The law of conservation of mass states that, in a chemical reaction, or any action for that matter, mass cannot be created or destroyed. It can, however, go somewhere else. In a chemical equation, the mass of the products is the same as the reactants, even if one of the products is a gas, unless the gas is trapped in a sealed-off container. The mass does not change, regardless of the phase change or the factors being combined, because all atoms are accounted for.
Problems:
2.) Explain how the law of conservation of mass applies to garbage. The law of conservation of mass applies to garbage in that garbage sits in landfills for years, and only some of it biodegrades. What doesn't biodegrade still has matter--and mass, because it exists. We recycle that garbage by taking it and making it into usable products, like bottles, recycled paper, whatever have you. The mass of the garbage is not lost, but it changes forms.
7.) What would you have to do to prove that matter is conserved when a piece of paper is burned? The paper would have to be burned in sealed-off container, such as a glass box or something of that sort. That way, once the paper is burned, both its ashes and any gas released from the burning process is still present. Just find out the mass of the box with a scale.
Unit 4, Lessons 1 and 2
Lesson 1:
A chemical equation illustrates what happens, and what substances are involved, in chemical reactions. They are a way that scientists keep track of matter. Most chemical equations write out the substances involved in a reaction in the same way that mathematicians do. One one side of the equation, two reactants are added together, and on the other side, addition is also used. A further example is:
A chemical equation illustrates what happens, and what substances are involved, in chemical reactions. They are a way that scientists keep track of matter. Most chemical equations write out the substances involved in a reaction in the same way that mathematicians do. One one side of the equation, two reactants are added together, and on the other side, addition is also used. A further example is:
2HCl(aq) + Cr(s) --> CrCl2(aq) + H2(g)
Which is read aloud as:
"An aqueous solution of hydrochloric acid reacts with solid chromium to produce an aqueous chromium chloride solution and hydrogen gas."
Not everything about a chemical reaction can be observed through the senses, which is why these equations exist! Two substances, like hydrochloric acid and water, water and salt water, things like that...can all be clear, and therefore we might not be able to tell the difference between them.
Problems:
1.) What is the difference between reactant and a product? A reactant is what is combined with another substance (another reactant) in a chemical equation. The product is what the reactants make, and usually marks the end of the reaction.
6.) Describe at least three types of effects that a toxic substance can have on the body. If ingested, a toxin can cause severe nausea, diarrhea, blood acidosis, or possibly even kidney stones. If taken in through the nose, perhaps even the skin, hallucinations can occur.
Lesson 2:
In addition to specifying which substances are what, chemical equations also clue us in to possible phase changes. From them, we can predict what we might observe during a reaction. For example, the equation in Lesson 1 tells us that an aqueous solution and a solid come together to create a liquid with a solid precipitate (another aqueous solution) and a gas. There will probably be some bubbling, some evaporation, to produce the hydrogen. If we have bubbles rising, we might need some heat, so a temperature change could also be observed.
Problems:
2.) Use chemical equations to describe the difference between sugar melting and sugar decomposing. The formula for sugar is C12H22O11. The melting process of sugar is a physical change, because sugar molecules don't have to change their identity. The chemical equation or melting sugar is C12H22O11(s) --> C12H22O11(l), and vice versa as sugar sets afterwards. Decomposing sugar, however, involves the splitting of sugar molecules. They break apart, as the word suggests. The chemical equation for decomposing sugar is C12H22O11(s) --> 12C(s) + 11H20(g).
4. Write a chemical equation for these reaction descriptions:
A.) Solid sodium chloride dissolves in water. NaCl(s) + H2O(l) --> NaCl(aq)
B.) Solid magnesium sulfide is heated to produce solid magnesium and sulfur gas. MgS(s) --> Mg(s) + S(g)
C.) Solid titanium is heated in oxygen gas to produce titanium dioxide. Ti(s) + O2(g) --> TiO2(s)
Friday, October 12, 2012
Unit 3, Lesson 19
Hurricanes form in stages, the first being a tropical depression, which is simply an area of low pressure that has the potential to produce heavy precipitation. The tropical depression has the power as it makes its way toward land to develop into a tropical storm, which is a phenomenon that can drop lots of rain with lots of wind. At the hurricane stage, rain causes flooding and winds become so violent that homes can be destroyed, sometimes even leveled. The eye of a hurricane, which has been speculated to be the safest place in the storm, is a core of cold air around which clouds spin continuously. The spinning, and winds around the storm, push it in different directions.
Problems:
1.) What conditions are necessary for hurricane formation? For a hurricane to form, the following conditions must be present: low air pressure, winds of or above 75 mph, moist, warm air rising from the ocean, and cloud formation high in the sky in a spiral pattern.
Problems:
1.) What conditions are necessary for hurricane formation? For a hurricane to form, the following conditions must be present: low air pressure, winds of or above 75 mph, moist, warm air rising from the ocean, and cloud formation high in the sky in a spiral pattern.
Unit 3, Lessons 17 and 18
Lesson 17:
This unit tacked on another gas law to the three we've already learned about. It's called the ideal gas law, and it's described by this formula!:
This unit tacked on another gas law to the three we've already learned about. It's called the ideal gas law, and it's described by this formula!:
PV = nRT
Check my summary for lesson 16 to remember what the letters stand for. This equation is helpful in finding almost anything you need and is closely associated with STP: standard temperature and pressure. Typically we use the ideal gas law to find out the volume or or the number of moles present in a sample of gas.
Problems:
3.) How many moles of hydrogen, H2, gas are contained in a volume of 2 L at 280 K and 1.5 atm?
PV = nRT
(1.5)(2) = n(0.082)(280)
3 = n(22.96)
n = 0.13 mol, there are 0.13 moles of hydrogen in his sample.
Lesson 18:
Humidity is defined as the amount of water present in an air (see: Florida). Humidity increases or decreases by evaporating from a larger body of water or by condensing onto a solid object, such as a glass of ice water (why glasses of tea "sweat"). The total number of moisture in the air is called relative humidity and cannot exceed 100%, but can be determined by finding the difference between the readings on a dry-bulb and wet-bulb thermometer. Warm air can hold more water than cold air, which explains why clouds form on cold days.
Problems:
1.) What does humidity measure? The amount of water present in the air.
Unit 3, Lessons 15 and 16
Lesson 15:
A plane in flight gains elevation after lifting off the runway. Passengers in the plane's pressurized cabin don't feel the change, but outside the plane, the pressure and temperature of the air decreases and breathing becomes difficult. There aren't as many molecules at high elevations to support life or respiration, so gases are lighter and, ultimately, colder. Hence, the relationship between altitude, pressure, and density. The number of molecules, however many there may be, can be described by the term number density, which is represented by the following formula:
A plane in flight gains elevation after lifting off the runway. Passengers in the plane's pressurized cabin don't feel the change, but outside the plane, the pressure and temperature of the air decreases and breathing becomes difficult. There aren't as many molecules at high elevations to support life or respiration, so gases are lighter and, ultimately, colder. Hence, the relationship between altitude, pressure, and density. The number of molecules, however many there may be, can be described by the term number density, which is represented by the following formula:
n/V
where n is the number of moles--a fancy term used to describe how many atoms there are in a sample of gas.
Problems:
2.) Use the kinetic theory of gases to explain the relationship between number density and gas pressure. As I stated in my summary of this lesson, as pressure increases, there are more molecules condensed into a space, and vice versa. If the pressure drops, there are less molecules. The molecules don't change the speed at which they fly, but there are less of them, which means they don't bump into one another/change direction as often.
Lesson 16:
Our friend the mole is represented by the number 6.022x10^23, or 602 sextrillion--huge! Moles are measurements of how many atoms, particles, whatever-you-want-to-call-them there are in a sample of gas. If you don't know how many moles are present, use this nifty equation to figure it out:
PV = nRT
where P = pressure, V = volume, n = moles, R = the constant (0.082) for all gases, and T = tempterature (in Kelvin.) Though any value can be plugged in for those variables to find another, it's more common to see the equation used at STP, the standard temperature and pressure, which are 273 K and 1.0 atm.
Problems:
5.) Which has more atoms: 8.0 g of helium, He, or 40.0 g of argon, Ar? Explain. Both of these elements are noble gases, but argon is in a larger quantity, so I'd say 40.0 g of Ar has more atoms.
7.) At 25 degrees C, which balloon has the greater volume: an oxygen, O2, balloon at 1.2 atm with a mass of 16.0 g, or a helium, He, balloon at 1.2 atm with a mass of 2.0 g? By Avogadro's law, two samples of gas at the same temperature and pressure are said to have the same number of particles regardless of their mass. This, in turn, should make their volumes the same. The two balloons have an equal volume, but you'll need 8x as more He to equal O.
Sunday, October 7, 2012
Unit 3, Lessons 13 and 14
Lesson 13:
Sometimes all the variables in your sample of gas change. Say that your pressure increased or decreased, making for a rise or drop in temperature, and that influenced the sample's volume. What ever would you do to find that one missing piece? You'd use the Combined Gas Law, of course, which is as follows:
Sometimes all the variables in your sample of gas change. Say that your pressure increased or decreased, making for a rise or drop in temperature, and that influenced the sample's volume. What ever would you do to find that one missing piece? You'd use the Combined Gas Law, of course, which is as follows:
k = P(V) / T
Typically, we see this formula being used to solve equations like what I've described; the need to find a volume. It can also be called for in altitude problems, where say a balloon has risen to a higher altitude than sea-level and the pressure has changed.
Problems:
(WILL BE ADDED LATER)
(WILL BE ADDED LATER)
Lesson 14:
We've already found out that warm and cold fronts are associated with different kinds of weather, but whether you have a sunny day or a rainy day is also dependent upon what the air pressure is. Areas of low pressure are, as you could probably guess, associated with colder temperatures and more snow/rain. This happens because the cold air means that particles move slower, which allows for condensation, then clouds, and eventually precip. High pressure areas are warmer, sunnier, and more pleasant. When high and low pressure areas meet, the high pressure air rises above the denser cold pressure air.
Problems:
(WILL BE ADDED LATER)
(WILL BE ADDED LATER)
Unit 3, Lessons 11 and 12
Lesson 11:
Gay-Lussac's law tells us that the pressure of a given amount of gas is proportional to its temperature and that the volume of that sample will never change. Temperature, usually expressed in Kelvin, plays a role in this equation:
(WILL BE ADDED LATER)
Gay-Lussac's law tells us that the pressure of a given amount of gas is proportional to its temperature and that the volume of that sample will never change. Temperature, usually expressed in Kelvin, plays a role in this equation:
k = P/T
where k is the proportionality constant, as it was in Boyle's law. A simpler way to describe this law, and if you could picture it on a graph you'd see why, is to say that as temperature rises, the pressure increases, and while the pressure decreases, the temperature drops as well.
Problems:
(WILL BE ADDED LATER)
Lesson 12:
This lesson was relatively self-explanatory. The kinetic outlook on gases tells us that gas molecules are already in motion--which we knew. We can take this outlook and apply it easily. The more pressure you put on a sample of gas, the more you restrict the movement of the molecules inside. When you release pressure, those molecules move around quicker, at greater distances and speeds, resulting in a more flowy...I guess that's the world...yeah, more flowy gas.
Problems:
(WILL BE ADDED LATER)
(WILL BE ADDED LATER)
Unit 3, Lessons 9 and 10
Lesson 9:
This lesson told us all about pressure, which can be defined simply as the force with which particles in a sample of gas hit the sides of their container. Pressure is related to temperature and volume through the use of three laws: Boyle's, Charles's, and Gay-Lussac's. There exists a thing called atmospheric pressure, or atm, which is pressure that constantly weighs on everything on a planet's surface. Earth's typical atm is around 14.7 and can increase/decrease when you're at sea level or on top of a mountain.
Problems:
(WILL BE ADDED LATER)
Lesson 10:
You can use Boyle's law to help calculate varying pressures when volume is constant. When volume doesn't change, it's greatly possible that a gas sample is in a rigid container, or one that doesn't change size/shape, like a graduated cylinder, a bowl, box, or a beaker. The following equation represents Boyle's law:
(WILL BE ADDED LATER)
This lesson told us all about pressure, which can be defined simply as the force with which particles in a sample of gas hit the sides of their container. Pressure is related to temperature and volume through the use of three laws: Boyle's, Charles's, and Gay-Lussac's. There exists a thing called atmospheric pressure, or atm, which is pressure that constantly weighs on everything on a planet's surface. Earth's typical atm is around 14.7 and can increase/decrease when you're at sea level or on top of a mountain.
Problems:
(WILL BE ADDED LATER)
Lesson 10:
You can use Boyle's law to help calculate varying pressures when volume is constant. When volume doesn't change, it's greatly possible that a gas sample is in a rigid container, or one that doesn't change size/shape, like a graduated cylinder, a bowl, box, or a beaker. The following equation represents Boyle's law:
k = PxV
where k is your proportionality constant, or a value that stays the same in all calculations using Boyle's law. With this equation, you know that pressure and volume are indirectly proportional. When pressure increases, volume decreases, and vice versa.
Problems:
(WILL BE ADDED LATER)
Unit 3, Lesson 8
We've already discussed how molecules in samples of matter are in constant motion. However, some move slower than others, and particle speeds mean that we get these nifty things called phases. A phase is a physical change that matter goes though and can be solid -> liquid (melting), liquid -> solid (freezing), liquid -> gas (evaporation), or solid -> gas (sublimation.) Matter also has density. Depending on its phase, a sample can have a different density. For example, as I've already briefly touched on, ice is a phase of water and it is more dense than liquid water. Snow is less dense than water, even though it's frozen, because it has smaller pieces and you'd need more of it to equal the volume or density of its solid/liquid counterparts.
Problems:
(WILL BE ADDED LATER)
Problems:
(WILL BE ADDED LATER)
Sunday, September 30, 2012
Unit 3, Lesson 7
Weather fronts act as the forces that push high and low pressure systems around all over the country and all over the globe. These high and low pressure systems are called air masses, and they can either be warm and dry and nice or cold and snowy and miserable. They are called cold fronts and warm fronts and bring with themselves unique traits--and densities. The density of a cold front is greater than that of a warm front because of the expansion of gases in warm fronts that cause them to rise above cold fronts. Sometimes, these two air masses meet and clouds form, dropping precipitation. We often hear about tornadoes forming in areas where cold fronts and warm fronts collide. Cold fronts tend to spit out precipitation in violent bursts whereas a warm front might only drop a slight drizzle over a region. Almost always, the location of an air mass is also the location of cloud cover and high/low pressure.
Problems:
4.) A cold front is approaching your town, expected to arrive tomorrow. What kind of weather can you expect? The cold front will most likely cause a drop in temperature, thicker clouds, and the potential for either a lot of drenching rain or a lot of snow. I'd best set out my beanie!
5.) A warm front is approaching your town, expected to arrive tomorrow. What kind of weather can you expect? I might prepare for an increase in temperature, perhaps slight rain, and possible cloud cover. If clouds do form, they might be light and airy rather than thick and clumpy and overcast.
Problems:
4.) A cold front is approaching your town, expected to arrive tomorrow. What kind of weather can you expect? The cold front will most likely cause a drop in temperature, thicker clouds, and the potential for either a lot of drenching rain or a lot of snow. I'd best set out my beanie!
5.) A warm front is approaching your town, expected to arrive tomorrow. What kind of weather can you expect? I might prepare for an increase in temperature, perhaps slight rain, and possible cloud cover. If clouds do form, they might be light and airy rather than thick and clumpy and overcast.
Unit 3, Lesson 6
This was quite a gassy lesson!
...No...? Oh, alright. Moving on...
We discussed Charles' Law. Charles' Law simply states that the volume and temperature of a gas sample are proportional to each other through the use of a constant, which we represent as a lowercase k. The equation for finding the constant, k, the volume, or the temperature of a sample is as follows:
...No...? Oh, alright. Moving on...
We discussed Charles' Law. Charles' Law simply states that the volume and temperature of a gas sample are proportional to each other through the use of a constant, which we represent as a lowercase k. The equation for finding the constant, k, the volume, or the temperature of a sample is as follows:
V= kT
k = V/T
T = V/k
The proportionality constant varies depending on the size of the sample of gas that you have.
Problems:
1.) Explain how to find the proportionality constant for a sample of gas. If you know that you can find volume by multiplying k and the temperature of your sample, you can scramble the equation (which I have so graciously done above) and divide volume by temperature to get your constant.
4.) A sample of gas in a cylinder has a volume of 980 mL at a temperature of 27 degrees Celsius. If you allow the piston to move while you heat the gas to 325 K, what will the volume of the gas be at 130 degrees C?
27 degrees C = 300 K. 130 degrees C = 403
980/300 = 3.26
403(3.26) = 123.6 or about 124 mL
Unit 3, Lesson 5
Here, we were introduced to the third and final temperature scale (remember how I mentioned there being three in my lesson 4 post?). It's called the Kelvin scale. It does not require the use of a degree mark, only a capital K. Associated with Kelvin is the term 'absolute zero', which is a temperature we haven't been able to reach, but have gotten quite close to. To find a Kelvin temperature, you can use these formulas:
K = C + 273
C = K - 273
As a side-note, keep in mind that molecules/particles in a sample of gas are always moving. An object in motion will stay in motion unless an outside force interferes with it. Particles travel in straight lines until they bump into each other or into a wall.
Problems:
5.) Which unit is the smallest: one Celsius degree, one Kelvin, or one Fahrenheit? You find a Kelvin degree by adding 273 to a Celsius degree, which makes Kelvins the biggest units of temperature and Celsius the next step down. Because a Celsius degree can encompass many Fahrenheit degrees, Fahrenheit is the smallest unit of temperature measurement.
9.) Convert these temperatures to the Kelvin scale.
A.) 95 degrees F (hot day)
95 = 1.8(C) + 32 K = C + 273
-32 -32 K = 35 + 273
------------------- K = 308
63 = 1.8(C)
-------------------
C = 35
B.) 350 degrees F (oven temperature)
350 = 1.8(C) +32 K = C _273
-32 -32 K = 176.6666666666667 + 273
----------------------- K = about 450
318 = 1.8(C)
-----------------------
C = 176.6666666666667 (didn't round yet!)
C.) 5 degrees F (freezer temperature)
5 = 1.8(C) + 32 K = C +273
-32 -32 K = -15 + 273
------------------ K = 258
-27 = 1.8(C)
------------------
C = -15
5.) Which unit is the smallest: one Celsius degree, one Kelvin, or one Fahrenheit? You find a Kelvin degree by adding 273 to a Celsius degree, which makes Kelvins the biggest units of temperature and Celsius the next step down. Because a Celsius degree can encompass many Fahrenheit degrees, Fahrenheit is the smallest unit of temperature measurement.
9.) Convert these temperatures to the Kelvin scale.
A.) 95 degrees F (hot day)
95 = 1.8(C) + 32 K = C + 273
-32 -32 K = 35 + 273
------------------- K = 308
63 = 1.8(C)
-------------------
C = 35
B.) 350 degrees F (oven temperature)
350 = 1.8(C) +32 K = C _273
-32 -32 K = 176.6666666666667 + 273
----------------------- K = about 450
318 = 1.8(C)
-----------------------
C = 176.6666666666667 (didn't round yet!)
C.) 5 degrees F (freezer temperature)
5 = 1.8(C) + 32 K = C +273
-32 -32 K = -15 + 273
------------------ K = 258
-27 = 1.8(C)
------------------
C = -15
Saturday, September 29, 2012
Unit 3, Lesson 4
Though Chemistry includes three temperature scales, this lesson only touched on two: Celsius and Fahrenheit. Substances become hot or cold depending on how fast their molecules are moving. Keep in mind as a side note that fast-moving particles usually result in gas that expands to take up more space. Hence, "excited" particles make for hotter temperatures. Alternatively, however, some particles move sluggishly and tend to cause gases to compact, or contract, which means that they get smaller. Similar to the way that a person curls into a ball with a blanket when they're cold, the compacted molecules make for cooler temperatures. At that point, we get ice.
Hotness and coolness are measured in Fahrenheit and Celsius through the use of the term degrees. The two scales are drastically different from one another. One increment in Celsius accounts for an enormous jump in degrees Fahrenheit, which means that you could easily screw up a measurement if you don't pay attention!
A formula for converting Celsius from Fahrenheit is as follows:
Hotness and coolness are measured in Fahrenheit and Celsius through the use of the term degrees. The two scales are drastically different from one another. One increment in Celsius accounts for an enormous jump in degrees Fahrenheit, which means that you could easily screw up a measurement if you don't pay attention!
A formula for converting Celsius from Fahrenheit is as follows:
F = 1.8 (C) + 32
OR
F = 9/5 (C) + 32
Problems:
1.) Explain how the height of a liquid can be used to measure temperature. As the temperature of a substance increases, the particles in that substance begin to move faster and faster, growing more "excited" if you will, and that causes the liquid, gas, whatever you might have, to expand. If in a container, the expanding substance will grow and its height will increase. Liquid inside a thermometer rises to a certain tic mark on the side of a glass tube to tell the temperature of something.
5.) Convert -40 degrees C to F. Show your work.
F = 1.8 (-40) +32
F = -38.2 + 32
F = -6.2
F = -6 degrees
1.) Explain how the height of a liquid can be used to measure temperature. As the temperature of a substance increases, the particles in that substance begin to move faster and faster, growing more "excited" if you will, and that causes the liquid, gas, whatever you might have, to expand. If in a container, the expanding substance will grow and its height will increase. Liquid inside a thermometer rises to a certain tic mark on the side of a glass tube to tell the temperature of something.
5.) Convert -40 degrees C to F. Show your work.
F = 1.8 (-40) +32
F = -38.2 + 32
F = -6.2
F = -6 degrees
Unit 3, Lessons 2 and 3
Lesson two explained to us the proportionality between volume and height for different containers. In a container with a base shaped similar to the top, with parallel sides, volume and height are exactly proportional. If you change the size of your container, your height might change, but your volume won't. Lesson 3 gave us a more in-depth look at this. We learned the densities of rain and snow, which are as follows:
Rain - D = 1 g/mL
Snow - D = 0.5 g/mL
This occurs because snow is lighter, fluffier if you will, than liquid rain when you put it in a container. If you were to watch snow melt (wouldn't that be exciting) you'd have the same density as rain.
Certain formulas come in handy when you're trying to figure out mass, density, and volume. They are as follows:
Volume: V= M/D
Density: D= M/V
Mass: M= V x D
Lesson 2 Problems:
2.) Explain in your own words why meteorologists prefer to measure rain in inches or centimeters, not in milliliters or cubic centimeters. Meteorologists prefer to measure rain in inches or centimeters as opposed to milliliters or cubic centimeters because the last two units typically refer to volume, which can fluctuate depending on what type of container liquid is being kept in. Height, on the other hand, which is measure in inches or centimeters, does not depend on the diameter of a rain gauge or other container.
5.) If a large washtub, a dog's water dish, and a graduated cylinder were left outside during a rainstorm, would the three containers have the same volume of water in them after the storm? Explain why or why not. The three containers would not have the same volume of water in them after the rainstorm. While they all probably have circular bases and parallel walls, the base of the washtub is most certainly larger in diameter than that of the graduated cylinder, and the water dish falls between those two. Since volume is related to diameter and fluctuates based on the amount of space needed to be filled, the three containers might not collect the same volume. (I'm prepared for this answer to be terribly wrong.)
5.) If a large washtub, a dog's water dish, and a graduated cylinder were left outside during a rainstorm, would the three containers have the same volume of water in them after the storm? Explain why or why not. The three containers would not have the same volume of water in them after the rainstorm. While they all probably have circular bases and parallel walls, the base of the washtub is most certainly larger in diameter than that of the graduated cylinder, and the water dish falls between those two. Since volume is related to diameter and fluctuates based on the amount of space needed to be filled, the three containers might not collect the same volume. (I'm prepared for this answer to be terribly wrong.)
Lesson 3 Problems:
3.) How are snow and ice different? While they're both made of water, snow is often times fluffier and lighter than ice. Because snow crystals are like ice that's been shredded up, they have a lower density than solid ice, which you can hold in chunks in your hand. You can feel ice's weight. Density changes with physical changes, which means that the densities of liquid water, ice, and snow are all different.
8.) Suppose you have a box that is full and contains 500 grams of a substance.
A.) What is the volume of the box if the substance inside is corn oil? (The density of corn oil is 0.92 g/mL)
3.) How are snow and ice different? While they're both made of water, snow is often times fluffier and lighter than ice. Because snow crystals are like ice that's been shredded up, they have a lower density than solid ice, which you can hold in chunks in your hand. You can feel ice's weight. Density changes with physical changes, which means that the densities of liquid water, ice, and snow are all different.
8.) Suppose you have a box that is full and contains 500 grams of a substance.
A.) What is the volume of the box if the substance inside is corn oil? (The density of corn oil is 0.92 g/mL)
V = M/D
V = 500/0.92
V = 543. 47
The volume of your box is most likely about 543 mL.
Unit 3, Lesson 1
If you're ready for this new unit, put your hands up!
Anyone else excited...? No...?
Ah, well, I tried.
Today we discussed lesson 1 of unit 3. The lesson talked about weather maps and how meteorologists use them to predict what conditions a given region will experience. There are maps that chart out cloud cover, precipitation, temperatures for different areas, and where pockets of high and low pressure are found. In addition to these helpful tools, there are also maps that display fronts and the jetstream. The jetstream, a constant current of wind (similar to the current you might've heard about running through the ocean) that divides the country in half, travels at about 57 mph, 4 miles above the ground, in a west-to-east motion. It gives flights head-winds and tail-winds, which mean that if you're flying, you might arrive at your destination earlier or a tad late. Fronts are "waves" if you will that push temperature, cloud cover, and precipitation into areas north or south of the jetstream. The type of precipitation that falls varies in areas of high or low pressure, which means that the southern United States will generally be more humid, overcast, and wet than the north and midwest regions.
Problems:
1.) What substances are necessary in order for a planet to have weather? Substances that make up the atmosphere, like gases and water vapor, must be present in order for a planet to have weather. An atmosphere creates an apparatus around the planet in which weather phenomena can occur.
3.) What is a physical change? A physical change is any form that a substance takes after conditions around that substance change. An example of a physical change would be ice melting into liquid water on a hot day or when sitting at room temperature.
Anyone else excited...? No...?
Ah, well, I tried.
Today we discussed lesson 1 of unit 3. The lesson talked about weather maps and how meteorologists use them to predict what conditions a given region will experience. There are maps that chart out cloud cover, precipitation, temperatures for different areas, and where pockets of high and low pressure are found. In addition to these helpful tools, there are also maps that display fronts and the jetstream. The jetstream, a constant current of wind (similar to the current you might've heard about running through the ocean) that divides the country in half, travels at about 57 mph, 4 miles above the ground, in a west-to-east motion. It gives flights head-winds and tail-winds, which mean that if you're flying, you might arrive at your destination earlier or a tad late. Fronts are "waves" if you will that push temperature, cloud cover, and precipitation into areas north or south of the jetstream. The type of precipitation that falls varies in areas of high or low pressure, which means that the southern United States will generally be more humid, overcast, and wet than the north and midwest regions.
Problems:
1.) What substances are necessary in order for a planet to have weather? Substances that make up the atmosphere, like gases and water vapor, must be present in order for a planet to have weather. An atmosphere creates an apparatus around the planet in which weather phenomena can occur.
3.) What is a physical change? A physical change is any form that a substance takes after conditions around that substance change. An example of a physical change would be ice melting into liquid water on a hot day or when sitting at room temperature.
Thursday, September 20, 2012
Unit 1 review
In this unit, we learned about almost everything under the sun that relates to atoms, atomic bonding, and reactions. We began by learning about significant figures, which are a sidenote of sorts but still important when doing math in Chemistry. From there we touched on the periodic table, discussing its groups and their properties and the patterns that cause the table to look how it does today. By learning the groups, we acquired knowledge of what elements are quick to bond and which are not, and how violently some react with other substances (such as the elements in Group 1A in water). For a brief while we discussed what atoms are made up of, constantly reminding ourselves that atomic numbers are equal to the numbers of protons. Our plethora of lessons helped us learn about bonds, what keeps atoms together, and how things like electrons are found (their arrangement) in atoms.
Problems:
4.) Describe nuclear fission and nuclear fusion. While nuclear fusion implies that two nuclei are joined together in a display of heat and energy to create a new, bigger nucleus and a new element, nuclear fission requires one nucleus to be split apart into two smaller nuclei. The two products are usually of the same element, but are different from the atom that was split apart. Fission also requires generous amounts of heat and energy to occur.
7.) What are cations and anions? They are the positively and negatively charged atoms in a compound. Typically, their charges are balanced to come out with something neutral. The cations are positive, while the anions are negative (remember that nifty trick I mentioned a few posts back? No? Oh well...)
11.) A substance does not dissolve in water and does not conduct electricity. What kind of bond keeps it together? It is most likely bonded with network covalence.
Problems:
4.) Describe nuclear fission and nuclear fusion. While nuclear fusion implies that two nuclei are joined together in a display of heat and energy to create a new, bigger nucleus and a new element, nuclear fission requires one nucleus to be split apart into two smaller nuclei. The two products are usually of the same element, but are different from the atom that was split apart. Fission also requires generous amounts of heat and energy to occur.
7.) What are cations and anions? They are the positively and negatively charged atoms in a compound. Typically, their charges are balanced to come out with something neutral. The cations are positive, while the anions are negative (remember that nifty trick I mentioned a few posts back? No? Oh well...)
11.) A substance does not dissolve in water and does not conduct electricity. What kind of bond keeps it together? It is most likely bonded with network covalence.
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