Homemade Ice Cream Freezing Point
Ice cream can be a really cool experiment. This science experiment is useful to illustrate freezing point
depression, or as a fun introduction of chemistry. So lets do the Freezing Point Ice Cream Lab.

The physical properties of a solution and those of the pure solvent are illustrated in this experiment. The
difference in temperature between the freezing points of a solution and of the pure solvent, known as the
"freezing point depression" will be demonstrated.
Pure water freezes at 0oC and one atmosphere. The freezing point of salt and water can be lower than 0oc.
The decrease in temperature allows our milk and sugar to freeze and make ice cream. The freezing point
is the temperature at which there is an equilibrium between the solid and liquid phases of a substance.
The temperature when this occurs is specific for different substances. Freezing point depression is usually
used in climates where it snows. The salt is put on the roads to prevent ice from forming.

Freezing Point Depression

•        Large Ziploc Bag
•        Small Ziploc Bag
•        Thermometer
•        Measuring cup / Graduated Cylinder
•        Spoons
•        Ice Cubes
•        Sodium Chloride (large crystals/rock salt)
•        sugar
•        vanilla extract
•        whole milk
•        triple beam balance

Add 100 ml of milk, 17.0g sugar, 2 drops vanilla extract to small ziploc bag. Place in refrigerator for and
hour to chill.

Place small ziploc bag inside the large bag. Put 400g cubed ice and 102g sodium chloride in the large
bag. Allow the bag to rest on side for one minute. Flip the bag over, arrange the ice and allow it to remain
for another minute. Repeat this for 10 minutes. The ice needs to be moved around so that it
surrounds/covers the small bag. After 10 minutes, open bag and take temperature of ice/salt solution.
Remove small bag and rinse it off. Enjoy the treat

1.        At what temperature does water normally freeze?
2.        what was the temperature of our salt water solution?
3.        What do you think happened?
4.        What does the sodium chloride do?
5.        Where can we use this lesson in real life?

Now go and do the freezing point ice cream experiment with some friends.
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