Science Lessons for Summer School
Ice Cream Activity Joins Math & Chemistry Curriculum with Recipe Fun
Jun 24, 2007
July is National Ice Cream Month! Treat your summer school students to a lesson that includes measurement, freezing points, and a bowl of fresh homemade ice cream.
Content Areas: Physical Science, Math (fractions), Consumer Science
Supplies: Each pair or small group will need a zipper-style sandwich bag and a zipper-style gallon freezer bag, enough ice to fill the the larger bag twice, paper towels, a paper cup, a large measuring cup, measuring spoons, half-and-half, sugar, vanilla, a towel, a thermometer, small plastic bowls for the serving ice cream
Advanced Organizer:
- Break students into pairs or threes. Build on prior knowledge by asking students the freezing point of water. Students will likely already know that 32 degrees Farenheit (Zero Celsius) is the temperature at which water turns to ice. Write that temperature on the board. Then ask, "Always?" If students don't come to the conclusion themselves, remind them that, in colder climates freezing water can be melted using salt. Then tell them that, in fact, a 20% salt / 80% brine (salt water) solution will not freeze until -16.6 degrees Celsius.
- Now ask whether they can think of any practical uses of this knowledge. Undoubtedly students will respond that salt is used to melt ice on roads and sidewalks during the winter in Northern climes.
- As you pass out the ice cream ingredients to each group, explain this phenomenon also applies to making ice cream. In fact, it is through melting ice that the ingredients can be frozen.
- Distribute the ice cream recipe below.
Recipe:
- Fill the gallon freezer bag with three cups of ice. Place the thermometer into the ice bag and set aside.
- In the small bag, add 1/2 c. of half-and-half, two tablespoons of sugar, and 1/2 teaspoons of vanilla. (Optional: Groups may also add 1/4 c. mini-chocolate chips to the mixture.) Seal the bag and shake to mix the ingredients.
- Record the temperature of the ice in the larger bag, and remove the thermometer.
- Seal the smaller bag inside of the larger.
- Wrap the bags in towel and have students take turns shaking the mixture for five minutes. If the ingredients are not yet fully solidified, students may add more ice and salt to the larger bag and shake again for another five minutes or until the mixture has fully thickened into ice cream.
- Remove the smaller bag, and, use a paper towel to wipe any salt water from the outside of the bag.
- Record the temperature of the melted ice inside of the larger bag.
Conclusion:
As students serve and enjoy the ice cream, explain the science:
- When salt is added to the ice, the orderly arrangement of the ice crystals is disturbed.
- As the melting ice combines with the salt, the resulting brine solution has a lower freezing point. Ask students to share their end temperatures. They should not be surprised to see that the melted ice solution is actually colder than the original ice.
- The colder temperature freezes the food ingredients and creates ice cream.
Allow students to take the recipe home to share.
This lesson plan may be differentiated for students of different levels. Whereas younger students may not fully understand the idea of crystals and solutions, more advanced students may be intrigued by the specifics of the actual chemical changes
