Name:______

ICE CREAM AND THE TASTY PHASE CHANGE LAB

Purpose:

  • To investigate the effects of heat transfer on phase changes
  • To investigate the effects of temperature changes on physical changes

Problem:

Will Mrs. Gaffney’s class be able to create a phase change when trying to create ice cream from milk, sugar, salt, vanilla, ice and salt?

Background Information:

In order to have a phase change in matter, heat must be gained or lost. Phase changes occur all around us in everyday life. For instance, ice melts when a drink is left in a room at normal temperature. Water freezes when placed in a really cold temperature, as in the freezer. In this experiment, we will see how fast heat is lost in order to change the milk from a liquid to a solid state. This is also an example of a physical change in matter.

Hypothesis:

If heat energy is lost while performing this lab, then there will be a phase change and ice cream will be made.

Materials: 2% milk, rock salt, measuring cups, sugar, ice, measuring spoons, vanilla, thermometer, ziplock bags (pint & quart), spoons, towel, scissors, duct tape, toppings (optional)

Procedure:

1.Place ½ cup milk and 2 Tablespoons sugar into a small ziplock bag. Be careful not to spill! Then, use 2-4 drops of the flavor(s) of your choice. Color is optional; use 1-2 drops total.

2. Close the bag securely. Tear a piece of duct tape large enough to completely seal the bag. Put it on across the seal and check other edges/corners for potential leaks. If you suspect any, seal those with duct tape as well.

3. Mix the contents thoroughly and set aside.

4. Into the larger ziplock bag, place 2 cups of ice and ¼- ½ cup water. Mix the ice and water andtake the temperature of the water-ice bath. Record the temperature in the data table.

5. Add 6 tablespoons (3/8 cup) of rock salt to the larger size bag.

6. Place the smaller small ziplock bag into the larger bag and close the quart-size bag.

7. Use the towel to knead the bag gently with your hands, noting the time you begin. You should begin to see changes occur in the milk solution. Continue kneading the bag until the mixture in the small bag is solid (approximately 5 – 10 minutes). Look at the clock when you begin so that you can time how long it takes for the mixture to freeze. You still need a thermometer, a pair of scissors, and a spoon.

8. Take the temperature of the salt-ice mixture and record the temperature in the data section. Also record the time it took for the milk mixture to freeze.

9. Remove the small bag from the large one. Cut open the small bag and use your spoon to taste the ice cream. Enjoy!

Temperature of ice-water bath before adding salt / oC
Temperature of ice-water-salt mixture / oC
Time for freezing to occur

CLEAN UP: Please throw away used duct tape, the small used bag, and spoon. Wipe up any spills. Clean your table. Rinse out the large ziplock bag, dry it with a paper towel, and give it to me. DO NOT THROW AWAY LARGE ZIPLOCK BAG!!

Conclusion Questions:

  1. What state of matter was the milk when you began?
  1. What state of matter was the milk when you were finished?
  1. In order to change the phase of milk, what had to be removed?
  1. What happened to the heat energy that left the milk?
  1. Why was the salt added to the ice? (if you have no idea, grab a laptop and look up the answer!)
  1. Why did the outside of the bag get wet?