Chemistry

Sahomy

Sahomy Rodriguez

May 2nd, 2014

H18

Objecive: Is the creation of ice cream a chemical reaction?

Background Info:

Certain substance affect the state of ice. When salt is sprinkled on ice, for example, it causes the ice to melt. This chemical reaction is actually a heat energy transfer. Water freezes at 0°C. A saturated saltwater solution freezes at -32°C. What happens if you sprinkle salt on ice?

Salt melts the ice into a liquid by creating an endothermic reaction, lowering the freezing point of water.

Materials:

-1/2 cup of milk
-1/2 cup whipping cream(heavy cream)
-1/4 cup sugar
-1 tablespoon strawberry flavoring
-3/4 cup sodium chloride (NaCl) as table salt or rock salt
-2 cups ice
-1 quart Ziploc bag
-1 gallon Ziploc bag
-Thermometer
-Measuring cups and spoons
-Cups and spoons for eating your treat!

Procedure:

1. Add 1/4 cup sugar, 1/2 cup milk, 1/2 cup whipping cream, and 1/4 tbsp strawberry to the quart Ziploc bag. Seal the bag securely.

2. Put 2 cups of ice into the gallon Ziploc bag.

3. Use a thermometer to measure and record the temperature of the ice in the gallon bag.

4. Add 1/2 to 3/4 cup salt (sodium chloride) to the bag of ice.

5. Place the sealed quart bag inside the gallon bag of ice and salt. Seal the gallon bag securely.

6. Gently rock the gallon bag from side to side. It's best to hold the top seal or to have gloves or a cloth between the bag and your hands because the bag will be cold enough to damage your skin.

7. Continue to rock the bag for 10-15 mins or until the contents of the quart bag have solidified into ice cream.

8. Open the gallon bag and use the thermometer to measure and record the temperature of the ice/salt mixture.

9. Remove the quart bag, open it, serve the contents into cups with spoons and ENJOY!

How To Video: https://www.youtube.com/watch?v=J3mAKzaliAI

Data:

1.) What kind of ice cream are you making?
Strawberry Ice Cream
2.) Document the temperature of the ice in the gallon bag before adding the salt.
0°C
3.) Document the temperature of the ice/salt mixture in the gallon bag when the ice cream mixture begins to solidify.
-10°C
4.) What is the temperature difference before adding the salt and after mixing for 5 minutes?
0°C
5.) What is the temperature difference before adding the salt and after mixing for 10 minutes?
0°C

Conclusion:

1.) What kind of chemical reaction is the process of ice cream making, as done in our lab? Explain why.
The process of making ice cream is a synthesis chemical reaction. Ice cream is a combination of different chemical creating a much more complex product by reacting/coming all together.

2.) Explain why salt water is harder to freeze than plain water.
Salt water's freezing point has been lowered with the salt being added. NaCl molecules break down the ice and replace the original molecules creating the ice acting as a freeze block effect. Which makes it harder for it to bond easily together once again.

3.) Is the process of making ice cream a physical or chemical change? Explain your answer.
The process of making ice is a physical change. The ice cream never made a new substance nor combusted. Through tee process of making ice cream, it simply only changes it's form (State Of Matter).

4.) Why is salt used with the ice instead of sugar?
Sugar does not dissolve completely in cold water nor allows ice to absorb energy (endothermic reaction) as salt does to melt the ice. Sugar's amount of molecules per mole are not enough to lower the water's freezing point as salt does with it's six times as much more amount of molecules in one mole.

Sources:

http://classroom.synonym.com/salt-melt-ice-faster-sugar-2454.html
http://www.sciencebuddies.org/science-fair-projects/phpBB3/viewtopic.php?f=31&t=11447
http://www.chemistryislife.com/the-chemistry-of-ice-cream-1

http://chemistry.about.com/cs/howtos/a/aa020404a.htm

http://chemistry.about.com/od/lecturenotesl3/a/chemphyschanges.htm
http://chemistry.about.com/od/chemicalreactions/a/reactiontypes.htm

http://www.chemistryislife.com/the-chemistry-of-ice-cream-1