Activity 4 1-19-11 Dissolving

Show an image or animation or description of what is happening when water dissolves NaCl.

The water is a lot of H2O molecules with the H's being positively charged and the O's being negatively charged. When you add salt to water it is also negatively charged on one end and positively charged on the other end. The Na is positive and the Cl is negative because the Cl has a much higher electronegativity and so it gets the electrons. So the H2Os go and grab salt molecules and runs off with them. The H's grab the Cl's and the O's gran the Na's and it pulls the solid salt apart.

Why is the freezing point lowered when salt is added to water?

The freezing point is lowered because the heat is being put into the salt molecules so the water can pull them apart.  With the higher heat the salt is pulling, the freezing point goes down because you need it to get colder with the salt pulling in more heat. So because the salt is pulling in more heat and moving the molecules faster it causes melting to happen more than freezing. So had I had my water at exactly 32 F and put and ice cube in it it would stay the same size because the water is freezing and the ice is melting at the same rate. If you add salt though then the salt brings in heat and it begins to melt faster than freeze, so with salt the freezing point goes down because with salt it can't freeze as fast because the salt is busy keeping it warm.

Activity 3 1-19-11 Crystal Structures

Show crystal structures for NaCl (sodium chloride)and CaCO3 (calcium carbonate). what is the melting point for these two materials.

Melting point = 801 °C, 1074 K, 1474 °F

Melting point = 825 °C, 1098 K, 1517 °F

Activity 2 1-19-11 Weather and Bernoulli's principle

Describe some common weather occurrences in relation to the gas laws and characteristics we have been exploring.

This explains why there is always a strong wind off of a lake. I mostly just assumed it came off lakes because it was a large open area where wind could really get going or something, but now I see that it's because the lake is a much different temperature. There is an expansion of the molecules because of the heat of the sun and the temperature changes and differences.
As the water comes from the pacific over the west mountain ranges it drops lots of water as it starts to go up the mountain because it gets cooler as you go up. Then as you get over the mountain there is desert on the opposite side for the same, but opposite reason. With this you get chinook winds coming down the mountain. All the air comes down the mountain, and as it gets warmer it expands, and as it expands it needs more room so it goes faster.

What is the Bernouli Principle, provide an example or application of this.

If you decrease the pressure, you will increase the speed. And if you increase the pressure you will decrease the speed.

With the wing of an airplane you have air going over and under the wing. The air on the top goes over the wing much faster than the air on the bottom, but the slow moving air under the wing also pushes up on the wing. The air on the top has a lower pressure, which is why it goes over faster, and there is more pressure on the air under the wing, so it goes slower.That is Bernoulli's principle, that more density makes air move slower and less density allows air to move faster.

Activity 1 1-19-11 Ideal Gas Law

Gases
-The molecules are far apart. We know this because when you cool a balloon it will shrink because the molecules inside get colder, start moving slower and thus, get more dense.
-Different gases have different densities.
-Lots of movement.
-Diffuses rather slowly.

More temp= more volume (Direct)
Less pressure= more volume (Inverse)
Add molecules= more volume (Direct)

 32psi/305K = x/244k
(32psi/305K)(244K) = x
 25.6psi=x

Homework 1-18-11

How much does water expand?

Water is at a different density depending on the temperature. The relation between temperature and density is not linear. It expands as it gets less dense. It does this because it has to become less dense to expand; it only has so much matter. It also expands because the molecules are moving faster because they are warmer. By moving faster they bounce on the outside of the molecule faster and push outwards on it, making it larger.

Density of liquid water

Temp (°C)	Density (kg/m3)[17][18]
+100	958.4
+80	971.8
+60	983.2
+40	992.2
+30	995.6502
+25	997.0479
+22	997.7735
+20	998.2071
+15	999.1026
+10	999.7026
+4	999.9720
0	999.8395
−10	998.117
−20	993.547
−30	983.854
The values below 0 °C refer to supercooled water.

When is water the smallest?

At 4C water is the most dense. As you can see in the chart above it begins to expand to a gas as it gets warmer, and expands to a solid as it gets colder. When I froze the water I froze cold and hot water because I have heard hot water freezes faster and cold water boils faster. When my hot water froze it stayed at the same level in the cup, but my cold water froze and the level rose showing that it expanded. I think the hot water was less dense than the cold water, so when i froze it the level went down first and then up to its original level. Whereas the cold water was more dense at first so the level didn't go down as much before it went up, and thus had a higher level in the end.

What happens when salt is added to the water?

Adding salt lowers the freezing point of water. The salt is taking heat from the water to dissolve so the boiling point would also go up.

Does the amount of salt added affect the freezing point?

 The more salt, the more heat that would be required to dissolve it, so yes. 

No salt	salt	tons of salt
15	15	15
0	3	4
-4.5	-5	-5

I found that at first my no salt got colder sooner, with the saltiest getting colder the slowest. It would have more heat in it because of all of the dissolving salts, and so it would get colder slower. The one with no salt got colder fastest because it didn't have the salt  pulling in heat.

Activity 2 1-18-11 Molecular Masses

List the molecular masses of carbon dioxide, oxygen and helium.

carbon dioxide(CO2) = 44 g/mol

<sup>Oxygen(O2) = 32 g/mol

Helium(H) = 4 g/mol

Carbon = 12 g/mol

Molecular Mass is the relative atomic mass. So for Helium you can just see what the molar mass is easily. Oxygen is 2 oxygens so that is easy too and you just double it. For Carbon Dioxide I had to add up the mass of a carbon and 2 oxygen. 


H2O is 2 hydrogens and one oxygen. 16+1+1=18. so H20 is 18 g/mol. Thus, making it lighter than air. This is very important to us and the water cycle, especially evaporation, since if water wasn't lighter than air it couldn't float up to make clouds.</sup> 

Activity 1 1-18-11 Burning Candle Observations

What is burning? Show the chemical formula and an image of the structure.
Gases our burning. Our butane, CH3CH2CH2CH3, once given a spark will ignite and turn to flame if it has oxygen to burn. Then after you have your butane fire you turn it towards the wood and begin to try and start that on fire. It won't light at first because it is not hot enough to burn wood off turning it into a gas, as illustrated below.

 So only gases burn, and to get wood on fire you have to get it hot enough so that the wood starts to turn to gas, just like when you boil a pot of water to a certain heat and it starts to turn into a gas as parts of the water go shooting out of the pot into the air.

Write the chemical reaction.

 

So you take your fire, which in our case is C4H10 and not CH2O, but we are still burning a gas to make fire.

 

C₂₅H₅₂ + O₂ → CO₂ + H₂O

You burn the candle wax, which is the farthest to the left, and the burning also consumes oxygen. Water and carbon dioxide are both burned off from the fire and they are what is left.

Write the balanced chemical reaction.

 C₂₅H₅₂ + O₂ → CO₂ + H₂O unbalanced

C₂₅H₅₂ + 38 O₂ → 25 CO₂ + 26 H₂O balanced

I added 25CO2 to balance for the carbon on the left. I also had to add 26 H2O to the right to balance out for the H on the left. Then I added 38O to the left side to balance out for the new C and the new H to the left side, and now we have a balanced equation where we burn off as much stuff as we put in, because matter just doesn't disappear.

This is the balanced chemical reaction for when you burn butane.

2C4H10 + 13CO2 --> 10H2O + 8CO2

 

 I added a 2 to the first C4H10 because when balancing I would have been left with a half, which isn't possible, and I added a 2 so the half would become a whole.