Name:______Per:____
Tasty Phase Change Lab
Students will investigate phase change by making ice cream from milk, sugar, vanilla, salt and ice. In order to have phase change, heat must be lost or gained. Phase change occurs around us in our daily lives. In this experiment, we will see how fast heat is lost to change milk from its liquid state to a solid state. Write a hypothesis about how milk will turn into ice cream.
Hypothesis: ______
Materials:
· 1 cup Milk
· ¼ cup Sugar
· 1/3 cup Salt
· 1 tsp. Vanilla
· 2 cups of Ice
· Ziploc bags (1 gallon & 2 quart)
· Towel
· Thermometer
Procedure:
1) Place a dishtowel over your work area. Keep your work on your towel.
2) Measure and pour milk, sugar, and vanilla flavor into the small Ziploc bag. Carefully seal the bag, tape it closed and shake up the mixture.
3) Fill the large Ziploc bag half full of ice and take the temperature. Record the temperature in the data table below.
4) Add the salt to the ice and carefully mix together. Take the temperature of the ice/salt mixture and record the temperature.
5) Put the small bag into the larger Ziploc bag.
6) CAREFULLY SEAL THE BAG!!!
7) Take turns flipping the bag. Hold the bag by the corners. Keep flipping it over and over. Remember to keep the bag over the towel at all times. It should take about 15 minutes to freeze.
8) When you have ice cream, take the smaller bag out and wipe it dry.
9) Dump the contents of the larger bag as directed by the teacher.
10) Dish out the ice cream equally into the cups and ENJOY!
Procedure Step / Description / Measurement (C)1 / Temperature of ice in Ziploc Bag
2 / Temperature of Milk
3 / Temperature of flavor plus milk
4 / Temperature of ice with salt added
5 / Temperature of milk after shaking 1 minute
6 / 5 minutes
7 / 10 minutes
8 / 15 minutes
Conclusion Questions:
1) Was your hypothesis correct or incorrect and why?
2) What state of matter was the milk when you began the lab? When you finished the lab?
3) In order to change the phase of milk, what had to be removed?
4) What do you think happened to the heat energy that left the milk?
5) Why was the salt added to the ice? What effect do you think this had on turning the milk into ice cream?
6) Water in the ocean does not freeze at 0oC like pure water, why is this?
7) If you did not add the sugar would the ice cream have frozen faster? Why?
8) Why did the outside of the bag get wet? (Assuming the bag didn’t leak)
9) Heat energy is needed to change phase from solid to liquid. List the possible source of the heat needed for this phase change to occur. Which source do you think is the best possibility and why?