Three Weekly Questions, 5/09/14

1. What tasks have you completed recently?
2. What have you learned recently?
3. What are you planning on doing next?

1. I recently completed two mandatory end-of-course exams—-one for history and one for chemistry. I also helped plant a small apple tree and an infant grape plant, read three 300+ page books in the past month, cooked some delicious steak, swept up glass from a broken window, and committed mass-murder upon a colony of tiny, red ants. I also won two certificates from my school’s “underclassmen awards ceremony” earlier this week—-one for English and one for Physics.

2. Recently, I have spent time learning about civil rights in my history class; we learned about gases, gas laws, and how they can be used, in our chemistry class; and in my physics class, I learned about heat and heat-energy: latent heats of fusion and vaporization; how to find the energy required to melt/freeze or boil/condense a substance; how to find the energy required to change a substance’s temperature if given a mass, the change in temperature, and the substance’s specific heat capacity; and how to find a specific heat capacity using calorimetry, etc. More recently, I learned about black holes, wave motion and how to find the velocity of a wave if given its frequency and wavelength, and the electromagnetic spectrum (gamma rays, x-rays, visible light, infrared rays, radio, etc.).

3. I plan on cooking some breakfast on Mother’s Day, reading some more 300+ page books, and being almost overwhelmingly busy as the school year comes to an end and last-minute stuff must still be taught. I also plan on taking multiple final exams, celebrating one of my brother’s birthdays in two weeks, and going to a park sometime soon.

Since the Friday two weeks from now, May 23rd, would be the next scheduled “weekly update” for this chemistry class, yet school also ends for us that day, chances are this will be our  last “weekly update” for this class, though that isn’t certain. But if it is, I’ll go ahead and show how much progress I’ve made on that “Library” I talked about in a blog months ago near the start of this class:

My picture

My picture

My picture

Another picture of mine. I told you it would take months; the entire building is 112 x 182 blocks, and if each block is 1m3, then the total area is 20,384m2; and if you take into account the two blocks on each of the four sides that make up walls, then there are 19,800m2 of floorspace.

I don’t plan on finishing soon.

Airbags (Blog 10)

“There is not a car made now without an airbag.  Explain the basics of how an airbag works as well as how the gas laws are applied in this technology.”

How does an airbag work? Well, they start off as simple, folded up bags connected to an inflator mechanism that is usually full of solid sodium azide (NaN3). For a steering-wheel airbag, this inflator is, in turn, connected to a crash sensor in the steering column. If it ever unfortunate enough to have to work, then the sensor will signal the inflator, which in turn will send an electric spark  to ignite the sodium azide and produce nitrogen gas, enough so fast and in such quantity, that the airbag is fully inflated in about one-thirtieth of a second. However, this happens with such force that it can occasionally cause serious damage to the driver and passengers, and even death for small children (hence why they say you shouldn’t let kids sit up front until they’re like 13).

But how does nitrogen gas increase the volume? Well, it can be explained with gas laws. Avogadro’s Law states that under constant temperature and pressure, the number of moles of a gas in a space is directly proportional to the volume of that space. Meaning that if the amount of nitrogen gas increases by one-hundred fold, then the volume will increase by one-hundredfold. But the airbag can only get so big, and pressure is also directly proportional to the amount of gas at constant temperature and volume; once the airbag reaches its maximum volume, then it will become constant and so pressure must increase instead. But, if inflating a football has taught anyone anything, it’s that a soft container will become harder and more rigid as more air/gas is added to it. So how do designers keep airbags from becoming as hard and deadly as a concrete wall? They add many small holes to the airbag to let nitrogen vent out. This also creases a cushion; as the driver/passenger skyrockets forward, the airbag absorbs shock by forcing gas out of the holes, keeping the person relatively safe and intact. Charles’s Law also states that under constant pressure and number of moles, temperature increases with volume, but this law isn’t really important here.

Links for further airbag reading:
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Also, here is a video on an airbag deploying in slow-motion, for your viewing experience (but warning: some mild language).

Water Pressure

  • What relationship seems to exist between pressure exerted on the gas and the volume it occupied?

Today, we performed a very messy minilab involving large jars, funnels and hoses, and large amounts of water. The goal was to fill the jar with water using a funnel positioned at three distinct heights, until no more water would enter into the jar under normal atmospheric pressure, and gather data such as the height from the top of the water in the funnel to the floor, the height of the water in the jar, the volume of water in the jar, etc.

First and foremost, we did/are doing this minilab because gas is different than the other two normal phases of matter in a few cool ways. First, we should define “gas”: it is a fluid substance comprised of individual atoms (ex. O2), individual molecules (ex. CO2), or a mixture of both types (ex. air). Unlike solids, gases do not have a definite volume and expand to fill space. Unlike liquids, gases are compressible, meaning that the average distance between atoms in a gas can be reduced, making it pressurized. Unlike both other phases, the Intermolecular forces between gas atoms are weak, so the distances between individual atoms are often great and much larger than the size of the molecules, hence the other two differences.

When we added water to the jars (through a hose that passed through a rubber stopper to keep water and air in the jar), we concluded that the gas must have been compressed by the water because more stuff is being added to the jar; the volume that the gas can take up is decreasing and the gas has nowhere else to go, so it must be compressed.

My picture

My picture. Hopefully you can understand how the lab is set up now

After doing all three tests at the differing heights, we noticed that filling up the jar from a greater height allowed more water into the jar and pressurized the gas inside more than from a lower height. The volume of the gas higher up was, therefore, less than the volume of the gas at the lower height. Furthermore, this leads to the conclusion that the volume of a gas decreases as the pressure exerted on it increases. I think I can also assume this means that volume increases as pressure decreases. Pressure is inversely proportional to volume.

“Who cares about titration?” (Blog 8)

“Titration is the slow addition of one solution of a known concentration to a known volume of another solution of unknown concentration until the reaction reaches neutralization, which is often indicated by a color change.”

Basically, titration is the use of one chemical that you know the concentration of, to find the concentration of another chemical that you know the volume of. If you use an acid and a base, then you would add acid to the volume of base until they neutralized, which an acid/base indicator like phenolphthphthalphein (which is not recommended for use) could help show you.

From there, you could use the equation M1V1 = M2V2, which states that a substance of a known molarity and a known volume can be used to find the volume or molarity of that same substance when diluted, when you know the molar ratio in which the two chemicals react.

For example, suppose you had an antacid tablet–that nauseating, chalky magnesium bicarbonate stuff you take when you’re real sick. Normally, this shouldn’t dissolve; but let’s suppose it does, and you put 25mL of a solution into a flask. If you added a pH indicator like BTB to the tablet solution until it turned blue (and indicated a base), then dripped 12mL of nitric acid of a .75 Molar concentration into it until it turned greenish (and indicated the mixture was neutral), then you could find the concentration of the antacid solution. But you would also need the balanced equation for your work, which looks like this:
Mg(HCO3)2(aq) + 2HNO3(aq) –> Mg(NO3)2(aq) + 2H2O(l) + 2CO2(g). This tells you the antacid and acid mix in a 1:2 ratio.

First, we work with the amount of acid: (.75mol HNO3/1L) * (.012L) = .009mol HNO3
Next comes the molar ratio: (.009mol HNO3) * (1mol Mg(HCO3)2/2mol HNO3) = .0045mol Mg(HCO3)2
Finally, finding the concentration: (.0045mol Mg(HCO3)2) ÷ (.025L) = .18 Molar concentration. This means that there are .18 moles of magnesium bicarbonate in every one liter of the original solution.

 

Titration also helps when you’re adding a base to an acid, such as to determine the amount of citric acid in fruit juice. Suppose you start by taking 250mL of the fruit juice and like three drops of BTB, and assuming that everything but the citric acid is absolutely neutral. Then, drip in NaOH of 1.25 Molarity until the mixture changes from acidic yellow to neutral green, and find the amount of used–say, 589 mL. Then, balanced equation:
HC6H7O7(aq) + NaOH(aq) –> NaC6H7O7(aq) + H2O(l) (and assume citric acid has a single ionizable hydrogen atom)

So now, (.589L) * (1.25mol NaOH/1L) = .73625 mol NaOH
Then, (.73625mol NaOH) * (1mol HC6H7O7/1mol NaOH) = .73625 mol HC6H7O7
Last, (.73625 mol HC6H7O7) ÷ (.250mL) = 2.945 Molarity for the citric acid.
Or, if you wanted the mass of citric acid present, (.73625 mol HC6H7O7) * (192.124gHC6H7O7/molHC6H7O7) = 141 grams of citric acid in that 250 milliliter sample.

In conclusion, as you can see, titration is very useful.

“Cool” Chemical Reactions

In response to this six year-old web page on “chemical reactions”, I present my next blog. First order of business: determining real chemical reactions from fakes.

10. This is indeed a chemical reaction, because you can clearly see a gas being produced during the first second–one indicator of reactions– and because the event produces something new: sodium chloride, produced during the bonding of chlorine and sodium, which is the very definition of a reaction.

9. This is also a reaction, because the magnesium burns and that is one sign of a chemical reaction. I don’t think in the page works, so there’s one that I found.

8. Another reaction; something burns and a gas (oxygen) is produced.

7. This isn’t a reaction. There is no indicator of a chemical reaction besides the superconductor;s change in temperature, but change in temperature is found in both physical, such as melting water, and chemical changes, like burning paper, so it isn’t really an indicator at all.

6. I’m very certain this isn’t a chemical reaction, if only because the sodium acetate stays as sodium acetate and doesn’t change into anything else. It can be present as a solution or as crystals because phase changes aren’t chemical changes.

5. Hydrogels, of which I cannot find a short video to replace the one on the page that seemingly “does not exist”, do not work by chemical reactions. If that was so, paper towels soaking up water would be chemical reactions. The hydrogels remain as hydrogels and the water remains as water.

4. Sulfur hexafluoride isn’t a chemical reaction, because there isn’t even a second chemical named here. It’s just dense air, weighing in at about 137 g/mol compared to regular air’s average molar mass of 29 g/mol; about 4.7 times as dense.

3. Superfluid helium isn’t a chemical reaction, because if you remembered from up above, phase changes, such as from gas to liquid, aren’t chemical changes, no matter how awesome.

2. Obviously there wouldn’t be any smoke or fire if it wasn’t a reaction, so it must be a chemical reaction. And to clear any confusion, I’m very certain the reaction is the thermite’s component chemicals, and the thermite reacting with the liquid nitrogen. And thirdly, since that entry’s video is telling me that the video is private and therefore un-seeable, here is another video I found of the reaction.

1. This last event is a chemical reaction, though it isn’t easy to know why–especially when color changes are also present in both chemical and physical changes and therefore aren’t of any help.

Second order of business: balancing equations to applicable reactions.

10. 2Na + Cl2 –> 2NaCl; This is synthesis, and also redox.

9. 2Mg + CO2 –> 2MgO + C; This is single-replacement metathesis.

8. 6KClO3 + C6H12O6 –> 6KCl + 6H2O + 6CO2 + 3O2, supposing the reaction is between the potassium chlorate and the glucose sugar in the gummy bear. This reaction is kind of almost like combustion, maybe.

2. Thermite comes in many different combinations, so I’ll use ferric oxide and aluminum powder: Fe2O3 + 2Al –> Al2O3 + 2Fe; this is single-replacement metathesis, and is also redox.

1. The very second that I find a full list of reactants and products for one of these reactions, I’ll update this post. I don’t even know exactly what type of reaction this would be either.

Final order of business: determining my favorite one.

It would have to be the number 1 reaction, the “Briggs-Raucsher” reaction, because I can’t imagine how rare oscillating reactions like that are, because it made a whole lot of pretty colors, and because superconductivity and the magnetic properties thereof are not considered chemical reactions.

Three Weekly Questions, 4/25/2014

1. What tasks have you completed recently?
2. What have you learned recently?
3. What are you planning on doing next?

1. I beat my friend at a game of chess, during the last three minutes of our lunch break, in the first eight moves of the game, after having paused our game about three weeks ago. I also created a container for the egg drop project that our Physics teacher assigned to us, which worked until it tipped over at the last second and broke, meaning that the egg didn’t break due to the shock of falling, but of tipping over afterwards, so the design itself was successful.

2. In my chemistry class, I learned about the various types of chemical reactions, how the products of those reactions can be predicted, and how to balance reduction-oxidation reactions.  We also finished learning about the time period of the Cold War and its nearly rampant spread of Communism in my history class, along with the Space Race that came after it. In my physics class, we learned about this energy this week; kinetic and potential energy, elastic energy, the Law of Conservation of Energy, and how it can be used (like finding out how far a spring of a known “stiffness” was compressed based on how far it shot a 1 kg ball out of a 2 meter long barrel at a 45° incline).

3. On Monday, I plan on finishing the chemistry lab we had today, which involved making a specific amount of a certain concentration of the super-dangerous and super-corrosive chemical sodium hydroxide (lye). I also plan on learning more about heat energy in my physics class next week, and I also plan on going out later tonight for dinner somewhere, for my birthday today.

Solutions Minilab

Today, we made solutions of sugar-water and saltwater. Now, you might be wondering, “what’s a solution?” So let’s define a solution as a heterogeneous mixture of two or more pure substances. The first compound is called a solute, and it is the one that is dissolved when dropped into the other substance. The second compound is called the solvent, it is present in the largest quantity, and it is the one that actually does the dissolving part and breaks down the solute into either individual molecules or ions. Additionally, to be dissolved basically means “to be surrounded by water or some other liquid.”

Moving on, we couldn’t differentiate between the salt mix and the sugar mix with 100% certainty, so we decided to do some thinking. We reasoned that salt, NaCl, was an ionic compound while the sugar sucrose, C12H22O11, was not. We hypothesized that the salt itself might break down into its individual Na+ and Cl ions, and therefore it would conduct electricity if a current was passed through it. This also meant that the sugar wouldn’t conduct electricity, and also pure water wouldn’t either, since it isn’t really made out of ions, either. So, we used a little light bulb with metal prongs on it, stuck the prongs into the solutions, and found that saltwater conducted and made the bulb glow, and neither sugar water nor pure/deionized water didn’t conduct.

My picture

My first picture; This is sugar water.

 

My picture

My second picture; This is saltwater.

We also learned that a solution like saltwater was called an electrolyte, whose definition is “a solution composed of dissolved ions, which will conduce electricity.” By extension, a non-electrolyte is just “a solution that isn’t composed of ions, and so which doesn’t conduce electricity.”

Furthermore, here are some particle diagrams of our two solutions:

my picture

my picture

One of water’s properties is what is known as polarity: it has both positive and negative charges, depending on which side it faces; the side with the oxygen on it has a partial negative charge, and the side with the two hydrogens on it has a partial positive charge. This means that the oxygen atoms will face in towards the positive Na cations, while the hydrogen atoms will face in towards the negative Cl anions. However, the sugar molecules weren’t made out of ions, so they simply broke down into individual sucrose molecules instead of into ions, and so each molecule was still electrically neutral and didn’t attract any particular side of the water molecules.

Chemical Reactions Lab

Combustion, a type of chemical reaction. Also, my picture.

Combustion, a type of chemical reaction. Also, my picture.

This lab was actually one giant lab made out of 11 smaller labs, whose objective was to show us the various types of chemical reactions that can happen. Here are the balanced chemical equations for those 11 labs:

1. 4Fe(s) + 3O2(g) –> 2Fe2O3(s)

2. CaO(s) + H2O(l) –> Ca(OH)2(aq)

3. 2H2O2(l) —MnO2–> 2H2O(l) + O2(g)

4. 2NaHCO3(s) –> H2O(l) + Na2CO3(s) + CO2(g)

5. Ca(s) + 2H2O –> H2(g) + Ca(OH)2(aq)

6. Zn(s) + Pb(NO3)2(aq) –> Pb(s) + Zn(NO3)2(aq)

7. Na2CO3(aq) + Ba(NO3)2(aq) –> 2NaNO3(aq) + BaCO3(s)

8. Pb(NO3)2(aq) + 2KI(aq) –> 2KNO3(aq) + PbI2(s)

9. CaCO3(s) + 2HCl(aq) –> CO2(g) + H2O(l) + CaCl2(aq)

10. CH4(g) + 2O2(g) –> CO2(g) + 2H2O(g)

11. 4C2H5O2(l) + 9O2(g) –> 8CO2(g) + 10H2O(g)

But so all of those equations above were not painstakingly written in vain, how do we know for certain that they are actually chemical reactions? Well, there are three major indicators: a color change, the appearance of bubbles or fizzing, and a precipitate forms. And, at least one of each was seen during each minilab.For example, my partner and I observed bubbles appear during our first minilab (#3), which meant a gas was being produced that wasn’t already there. During our second minilab (#11), we burned ethanol and watched the liquid’s color change from clear to a brilliant blueish flame as it combusted (which is also another indicator of a chemical reaction).

My picture

My picture; bubbles are the tiny and fuzzy dots

Furthermore, the reactions were divided up into five sections: Section 1 (1, 2); Section 2 (3, 4); Section 3 (5, 6); Section 4 (7, 8, 9); and Section 5 (10, 11). This was done based on similarity, which is so reliable that I can even show simple, general example reactions, too:

Section 1: Two reactants that produced one product.  Ex: AB + C –> ABC
Section 2: One reactant that produced two or more products.  Ex: ABC –> AB + C
Section 3: One element or ion is replaced by another element/ion in a compound.  Ex:  A + BC –> AB + C
Section 4: Two compounds exchanged their elements/ions for those of the other compound.  Ex: AB + CD –> AD + CB
Section 5: Combustion, which usually results in only water and carbon dioxide.  Ex: CxHyOz + O2 –> CO2 + H2O

From those examples above,  I’m pretty certain that the products of reactions can be predicted because the reactants can just be plugged into one of the example reactions and a product(s) can be predicted based on the reactants’ ions, charge, and otherwise chemical composition.

Three Weekly questions, 4/11/14

1. What tasks have you completed recently?
2. What have you learned recently?
3. What are you planning on doing next?

1. I recently finished mapping out the classes that I will be taking next year, I 100%-completed the video game which I have been playing almost exclusively for the past ¾ of a year, and I (hopefully) found the area of this type of shape ( a semicircle with two semicircles in it, with half the first circle’s radius, repeated forever),

My picture

My drawing,

where the areas of all the black semicircles are subtracted from the areas of the blue semicircles; it should be (2π*r2) ÷ 5, where r is the radius of the largest circle. For example, if the radius of the largest circle was 7 inches, the area should be 98π/5 in.2, or about 61.575 in.2

2. I learned about World War II in my History class and how terrible it was, especially the invention of the atomic bomb, which is credited with ending the War. I also learned about limiting reactants in my Chemistry class, along with how to use them to calculate other information. In my Physics class, I learned more about angular/circular motion, how fast a satellite must travel to stay in orbit around the Earth if its height above the Earth is known, how to calculate how long it takes for that satellite to complete one orbit, and we translated the kinematic equations for straight travels into angular kinematic equations for angular travels.

3. I plan on playing some other video games, reading some of the huge stack of National Geographic magazines I was recently given, and I plan on trying to prepare for a small chess competition that will probably (not) be held here soon.

“White Powder & Unknown Liquid”, 4/01/14

My picture; Baking Soda and Vinegar

My picture; Baking Soda and Vinegar

Today and yesterday, we mixed sodium bicarbonate and sodium carbonate with acetic acid (vinegar) and sulfuric acid. Here are the balanced equations of those mixes (except for the last one, which we didn’t experiment with), with coefficients in bold:

Sodium bicarbonate + acetic acid: NaHCO3 + HC2H3O2 -> CO2+ H2O+ NaC2H3O2

Sodium carbonate + acetic acid: Na2CO3 + 2HC2H3O2 -> CO2+ H2O+ 2NaC2H3O2

Sodium bicarbonate + sulfuric acid: 2NaHCO3 + H2SO4 -> 2CO2+ 2H2O+ Na2SO4

Sodium carbonate + sulfuric acid: Na2CO3 + H2SO4 -> CO2+ H2O+ Na2SO4

My picture, a reaction

My picture, a reaction

 

In each one, the mass of the lost gas (carbon dioxide) must be calculated from other masses taken if the reaction isn’t in a sealed container, and the mass depends on the amount of solid present in the reaction. Here are the relationships for each mix:

1. 44.01g CO2 / 84.008g NaHCO3
2. 44.01g CO2 / 105.98g Na2CO3
3. 88.02g CO2 / 168.016g NaHCO3. Or, 44.01g CO2 / 84.008g NaHCO3
4. 44.01g CO2 / 105.98g Na2CO3

My picture; dangerous Sulfuric Acid :D

My picture; dangerous Sulfuric Acid 😀

 

So from this data, seemingly, the only factor in the ratio of gas produced is the type of solid in the reaction, whether sodium bicarbonate or carbonate or any other solid and gas, and so a solid-to-gas ratio would probably apply to any/all chemical reactions of this nature.

One final thing that is important to say, and that is that because a fixed amount of solid produces a fixed amount of gas, then a fixed number of solid molecules will produce a fixed number of gas molecules, so their molar quantities are also in a relationship. Their molar quantities must also be related because equal masses of solid and gas have different numbers of molecules, so we can’t know how many solid molecules will be left over after the reaction unless we know the actual number of atoms or moles of each substance there is. That is also evident in the coefficients of the equations above; one mole of sodium bicarbonate and one mole of acetic acid will produce one mole each of carbon dioxide, water, and sodium acetate; two moles of sodium bicarbonate and one of sulfuric acid begets two moles of carbon dioxide, two of water, and one of sodium sulfate, etc. That also explains why the molar relationships above use the molar masses of the solids and gases (and why the third one had two ratios: the first, based on the molar masses and the coefficients, and the second one, because they are both reducible by 2).