Ice Cream Lab
Assignment: Chemical Reactions of Making Ice Cream
Background: Certain substances 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 zero degrees celsius. A saturated saltwater solution freezes at negative thirty-two degrees celsius.
What happens if you sprinkle salt on ice?
It changes the point at which your 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 of milk
1/2 cup of whipping cream (heavy cream)
1/4 cup sugar
1/4 teaspoon vanilla or vanilla flavoring (vanillin)
3/4 cup sodium chloride (NaCl) as table salt or rock salt
2 cups ice
1-quart Ziploc bag
1-gallon Ziplac bag
Thermometer
Measuring cups or spoons
Cups and spoons for eating your treat!
Procedure: (Follow the directions carefully). *Video LINK- highlight the ingredient that is different.
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 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 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 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!
1. What kind of ice cream are you making? The ice cream that I made was vanilla ice cream.
2. Document the temperature of the ice in the gallon bag before adding the salt. -10 degrees Celsius.
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. 1 degree Celsius. *DO NOT PUT THE THERMOMETER IN THE ICE CREAM BAG.
4. What is the temperature difference before adding the salt and mixing for 5 minutes? -10 degrees Celsius
5. What is the temperature difference before adding the salt and after mixing for 10 minutes? -10 degrees Celsius
1. What kind of chemical reaction is the process of ice cream making, as done in our lab? Explain why.
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. 1 degree Celsius. *DO NOT PUT THE THERMOMETER IN THE ICE CREAM BAG.
4. What is the temperature difference before adding the salt and mixing for 5 minutes? -10 degrees Celsius
5. What is the temperature difference before adding the salt and after mixing for 10 minutes? -10 degrees Celsius
1. What kind of chemical reaction is the process of ice cream making, as done in our lab? Explain why.
The chemical reaction that was taken place in the process of ice cream making was endothermic reaction. It was an endothermic reaction because endothermic really means is occurring or formed with the absorption of heat. The ice absorbs the energ to melt so the heat is transferred for the environment to the ice, which is the explanation to why the the ice gets so watery so fast, and the ice cream forms into a solid state.
2. Explain why salt water is harder to freeze than plain water.
Salt water is harder to freeze than plain water because of something called "freezing point depression". Dissolving any solute in a solvent causes that solvent to to freeze at lower temperatures than usual than it would if it were pure, plain, water. The salt in the salt water causes this to happen.
3. Is the process of making ice cream a physical or chemical change? Explain why
The process of making ice cream is a physical change. It is a physical change because you are not changing it's chemical properties, you are only changing it's appearance. It is still ice cream but in a different state.
4. Why is salt used with ice instead of sugar?
Salt is used with ice instead of sugar because salt makes ice melt. Salt actually lowers the the freezing point of the ice, which is making it colder than what it is normally. Water normally freezes at 32 degrees Fahrenheit, or 0 degrees Celsius.
Sources:
http://www.kentchemistry.com/links/matter/physicalchemicalchanges.htm
http://science.howstuffworks.com/nature/climate-weather/atmospheric/road-salt.htm
http://antoine.frostbug.edu/chem/senses/101/solutions/faq/why-salt-melts-ice.shtml
http://engineering.oregonstate.edu/momntum/k12/jul04/
