ice cream, make, chemical engineering, chemistry, chemical reaction, molecules, 1 Hour Total, 4-6
4, 5, 6
1 Hour Total
In this lesson, students make ice cream while learning about chemical engineering.
Learn a little bit about chemistry and chemical engineering.
Watch a chemical reaction in action.
For a class of about 20 students:
20 quart sized zip-lock bags
20 gallon sized zip-lock bags
2 large bags of ice
5 cups of salt.
For each group put the following ingredients into one zip-lock bag. When the bag is full place doubled-up the zip-locked bag with another bag to be sure that the ice cream does not leak out.
1/2 cup whole milk
1/2 cup of heavy cream
1/4 cup of sugar
1 tsp of vanilla or vanilla flavoring
Students will want to eat the ice cream so you should have a cup and a spoon for each students
You can also use the worksheet and PowerPoint attached to explain the science behind making ice cream.
Preparation and Set Up:
This lesson has the potential to be very messy, so it is really helpful if you
think out how you are going to organize it before hand.
Break students into groups of two
Give each group an ice cream bag.
Give each group 2 gallon sized zip-lock bags
Give each group a worksheet
Set up the PowerPoint
Chemical engineers use chemistry to solve problems. Chemical engineers create many
of the substances we used today, such as cleaning products, explosives, and even
toys (silly putty!). Chemical reactions are the tools that chemical engineers use.
Chemistry is also used in the production of many food products. The action of
bread rising is actually a chemical reaction. In ice cream, you use the chemical
interaction between water and salt to freeze the cream.
To make ice cream you must make the ice cream mixture of cream, milk and sugar
lower than 32 degrees F or 0 degrees C. This can be done by surrounding the ice
cream in a solution of water and ice that is lower that 32 degrees.
When salt is dissolved in water, the salt crystals break into smaller pieces. These small
pieces, or atoms get in the way of water molecules that are trying to stick together to
form a solid (ice). When the temperature of water is 32 degrees water molecules are
able to slow down enough to form a solid. When salt is added, the salt molecules get
in the way of the water forming a solid, so it must be even colder for all the molecules
to slow down enough to freeze. This is why salt lowers the freezing point of water.
This means that the ice will thaw at a temperature lower than 32 degrees in the
mixture around the ice cream.
Show the students a PowerPoint or explain what chemical engineering is.
Also explain the chemistry behind mixing salt and ice. What happens to the temperature of the solution even though it is liquid (it is colder than 32 degrees).
If you can, it would be good to have a thermometer available to measure the temperature of ice/salt/water.
Have the students fill out a worksheet.
Now it is time to make ice cream.
Have the students place the ice cream mixture bag inside one of the gallon sized bags.
Place about 2 cups of ice (or more) into each gallon sized bag.
Add 1/2 cup of salt to each groups gallon sized bag.
Seal the bag.
Place the gallon sized bag into a second gallon sized bag and seal that bag as well.
Have the students hold the bags upright as they shake the bag.
The ice should melt and get very cold because of the salt.
Students should shake their bags for about 10 -20 minutes. Long enough for the ice to begin to melt, but not long enough that the water starts to warm up.
When the students have finished shaking, have them empty their salt/water mixture into a sink. Have a teacher divide each bag of ice cream and let the students try their homemade dessert.
Use a thermometer to measure the temperature of the ice and water as the