Vanilla Ice Cream Chemical Reaction

Deja Vasquez         Date: 4/29/14       Hmrm/Period: H-23/ 3rd

Background:

Certain substances affect the state of ice. When salt is sprinkled on ice, for example, it causes the ice to melt. The chemical reaction is actually a heat energy transfer. Water freezes at 0 degrees celsius. A saturated saltwater solution freezes at -32 degrees celsius. 

Question: 

What happens if you sprinkle salt on ice?

It melts because it changes the point at which the substance freezes.

Objectives: 

To develop observation skills, understand the scientific process through active experimentation and comparison, and understand that chemicals can change the properties of water.

Materials:

• 1/2 cup milk
• 1/2 cup whipping cream (heavy cream)
• 1/4 cup sugar
• 1/4 teaspoon vanilla or vanilla flavoring (vanillin)
• 3/4 cup sodium chloride as rock salt
• 2 cups ice
• 1-quart Ziploc bag
• 1-gallon Ziploc bag
• Thermometer
• Measuring cups and spoons
• Cups and spoons for your ice cream!

Source: http://assets.kitchendaily.com/

Procedure:

1. Add 1/4 cup sugar, 1/2 cup milk, 1/2 cup whipping cream and 1/4 teaspoon vanilla to the quart Ziploc bag. Seal bag securely.
2. Put 2 cups of ice into the gallon Ziploc bag.
3. Use the 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 it by 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 minutes or until the content 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!

Source: Youtube video by Jessica Kim.

Data:

1. What kind of ice cream are you making? Vanilla 
2. Document the temperature of the ice in the gallon bag before adding the salt. n/a
3. Document the temperature of the ice/salt mixture (not the ice cream) in the gallon bag when the ice cream mixture begins to solidify. -5˚ celsius 
4. What is the temperature difference before adding the salt and after mixing for 5 minutes? -5˚ celsius 
5. What is the temperature difference before adding the salt and after mixing for 10 minutes? -9˚ celsius 

Conclusion: 

1. What kind of chemical reaction is the process of ice cream making, as done in our lab? Explain why. Endothermic because the substances that are reacting are gaining energy in order to react. As salt mixes with water an endothermic process occurs. Heat is coming from the cream and sugar, causing the once liquid milk and sugar to lose energy and become solid ice cream.
2. Explain why salt water is harder to freeze than plain water. Salt water is harder to freeze because salt water has a much lower freezing point than plain water. Plain water has no other substances in it so it is quicker to freeze. Salt in salt water lowers the freezing point of water which takes longer to freeze.
3. Is the process of making ice cream a physical or chemical change? Explain your answer. The process of making ice cream is a physical change because only the appearance is changing with the change of temperature. No chemical changes are being made. All that we make with ice cream can be reversed back to what it was.
4. Why is salt used with the ice instead of sugar? Salt is used because the property it has is that it lowers the freezing temperature of water. Salt has ions and sugar does not. Salt is melted at a much higher temperature because of its ionic bond. Sugar does not have that effect.

Works-Cited: 

http://curiosity.discovery.com/question/why-there-salt-ice-cream
http://www.kentchemistry.com/links/Matter/PhysicalChemicalChanges.htm
http://chemistry.about.com/cs/howtos/a/aa020404a.htm