Homework 1/18/11

Water Expansion with Salt Water

I had 3 cups, each filld with 2/3 c of water.  I put the cups outside and I checked them after 2 hours, 4 hours (which I did not put on my graph) and 9 hours.  One was my control which had no salt and froze within 3 hours.  At 2 hours the control was semi-frozen with just some water.  When I checked 9 hours later the water was completely solid and had some bubbles.  It was pretty smooth and had no excess water. 
The second cup I had I put just 1 Tsp in and when I checked it at the 2 hour point the water had started to form slush.  After 9 hours it was semi-frozen and a little more rough than the control cup.  This cup was the warmest cup at this point. 
The third cup I put in 3 Tsp and when I checked it after 2 hrs, it was the coldest of all of the cups.  It however, was barely slushy.  It was the cloudiest looking one, which makes sense.  When I checked it after 9 hours, it looked partially frozen and was very rough looking.  It was also the coldest at this time. 

It was hard for me to scientifically measure if the cups expanded, however I did notice that the control cup did expand after about 3 hours.  However, I could not really tell if the other two expanded. 

When salt is added to water the freezing point decreases.  So that is why the cup with salt was colder, but not frozen.  The more salt, the colder it must be to freeze.  The molecules interfere with one another making it difficult for the elements to freeze together. So yes, the amount of salt affects the freezing point. 

Activity 3 - 1/20/11

Make observation of excited gases.

Neon: Bright orange. When looking through the glasses I see two different color spectrums.  Much brighter, can see all colors, they are very close together.  A lot more lines than Helium

Helium: Dull yellow. the spectrum colors are more spread out, fewer lines, and not as bright.

Argon: is purple-ish. The colors are much more dull than the others.

Nitrogen: pink.  Lines are very close together and pretty bright. 

Carbon dioxide: very pale blue: The colors are dull and and very close together.

Activity 2 - 1/20/11

Write the formula for Tums?  How does Tums chmeically react with water and stomach acid?
CO3^-2 + H^+ ---> HCO3^- + H^+ ---> H2CO3 <----> H20 +CO2 = Evolution of Gas

How many Tums are needed to neutralize a can of coke?
1 tab?

Activity 1 - 1/20/11

Reflect on the expansion of water and salt water experiments you and your classmates performed.  What are some of the interesting results and struggles with this experiment. 
I found this activity pretty interesting, however, slightly predictable.  I knew that water with the most salt was not going to freeze as quickly as the control, if at all.  I did think it was cool to see the differences in the control (no salt), the water with 1tsp, and the water with 3 tsp and how they froze or turned to slush.

The thing about this experiment that I found the most difficult, was measuring the expansion.  I wish I would have bought the plastic see-through cups so I could have measured before and made a starting line and then it would have been a little easier.  Instead I used plastic colored cups that were slightly funny shaped, with a few curves and it was difficult to see a difference. 

Relate your thoughts on this experiment to the scientific question "Is the earth warming?"
The greenhouse effect is the idea that gases in the atmosphere is the reason the temperature gets hot, and can become freezing.  The gases trap the air such as a greenhouse for plants.  In the study of the greenhouse effect, there is no control unlike our experiment. 

http://www.epa.gov/climatechange/kids/greenhouse.html

Activity 5 - 1/19/11

PH 3 compared to PH 4
1. Which is more acidic? PH 3
2. By how many times? 10X

Activity 4 - 1/19/11

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

Sodium Chloride is ionic, so when it dissolves water molecules attatch to the sodium and chloride ions and they then seperate.  The positive Hydrogen molecules are attracted to the negatively charged Chloride ions and the negatively charged Oxygen is attracted to the positive Sodium ions. 

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

The Na+ and the Cl- get in the way of the water molecules making it harder for them to rearrange and become crystals.  Meaning, the salt water remains in a liquid state longer as the temp reduces. 

Activity 3 - 1/19/11

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

Sodium Chloride = the melting point is 1472*F

Calcium Carbonate melts at 1517*F