Homemade Ice Cream Challenge

Overview of Lesson

This lesson teaches students about chemical and physical changes and the addition of fractions.

 

Goal

Students will convert between Celsius and Fahrenheit, add fractions and learn about percentages. They also will understand how temperature affects food.

Objectives

• Students will convert temperatures from Celsius to Fahrenheit.

• Students will add fractions.

• Students will be introduced to percentages.

• Students will be introduced to how freezing affects food.

• Students will determine if making ice cream is a chemical or physical change.

Ohio Academic Content Standards

Mathematics
Measurement (Grade 5)

Benchmark B:
Convert units of length, area, volume, mass and time within the same measurement system.

Benchmark E:
Use problem-solving techniques and technology as needed to solve problems involving length, weight, perimeter, area, volume, time and temperature.

Indicator:
5. Make conversions within the same measurement system while performing computations.

Science
Physical Science (Grade 6)

Benchmark A:
Relate uses, properties and chemical processes to the behavior and/or arrangement of the small particles that compose matter.

Indicator:
3. Describe that in a physical change (e.g., state, shape and size) the chemical properties of a substance remain unchanged.

Science
Physical Science (Grade 4)

Benchmark A:
Compare the characteristics of simple physical and chemical changes.

Indicator:
2. Identify characteristics of a simple physical change (e.g., heating or cooling can change water from one state to another and the change is reversible).

Materials

• Ingredients listed in ice cream recipe

Procedure

1. Read scenario to students.

2. Have students make temperature conversions on worksheet.

3. Have students make recipe adjustments on worksheet.

Evaluation

Note: At the teacher’s discretion, older students may use the formulas given on the worksheets to convert temperatures from Celsius to Fahrenheit, and the reverse. For younger students, the teacher may go to the following Web sites for temperature converters: www.image-ination.com/test_maker/convert.html

 

Answer Page: The Homemade Ice Cream Challenge

Scenario:
The Corner Ice Cream Parlor regularly purchases its ice cream from a dairy company. One afternoon, several students asked the owner, Carl, if he would help them experiment with making homemade ice cream. Carl agreed, and with the help of the students, he immediately set out looking for a recipe and collecting the ingredients and necessary equipment.

Carl and the students found easy recipes for making the ice cream. What surprised them was the ingredient of rock salt. The freezing point to make ice cream is lower than 0 C (32 F) because there is sugar in the ice cream mixture. Rock salt is used to lower the temperature below freezing so that the mixture will freeze.

Converting temperature — use the following temperatures for practice
The temperature of the ice cream mixture can be controlled by the amount and ratio of rock salt and ice used. The more rock salt added to the ice, the lower the temperature. In the chart below are ice and rock salt concentrations and the temperatures. Convert the given temperatures to either Fahrenheit or Celsius.

Answers for pg. 78 — converting temperatures

Celsius Temperature 23.9 9 C 15.6 C 37 C 51.7 C 99 C

Fahrenheit Temperature 75 F 48.2 F 60 F 98.6 F 125 F 210.2 F

To convert from F (Fahrenheit) to C (Celsius), use this formula.
C = 5/9 x (F – 32)

Example:
Solve for F = 55 degrees
C = 5/9 x (55 – 32)
C = 5/9 x 23
C = 115/9
C = 12.8

 

To convert C (Celsius) from to F (Fahrenheit), use this formula.
F = (1.8 x C) + 32

Example:
Solve for C = 20 degrees
F = (1.8 x 20) + 32
F = 36 + 32
F = 68

 

Making Ice Cream

The recipe makes enough ice cream for two students. However, there are five students helping Carl. To make enough ice cream for everybody, the students will have to triple the recipe.

Ingredients (for two students) 1 tablespoon sugar 1/2 teaspoon vanilla 1/2 cup milk

Ingredients x 3 2 tablespoons sugar 1-1/2 teaspoons vanilla 1-1/2 cups milk

 

Plastic Bag Procedure

1. Have the students mix ingredients in a small plastic back that zips closed (the heavy-duty, freezer type).

2. Secure the bag and place it in a larger bag of the same type.

3. Fill the large bag half full of ice, surrounding the small bag.

4. Add 6 tablespoons of salt to the ice.

5. Close the large bag and shake it for five to 10 minutes.

6. The students can enjoy their own serving of ice cream! Add toppings if desired.

 

Coffee Can Procedure

This procedure uses a different recipe and method for making ice cream.

Ingredients:
2 cups whole milk (or add cream or powdered milk to 2 percent or skim milk)

1/2 cup sugar

1 teaspoon vanilla

3/4 cup rock, pickling or plain salt (larger crystals last longer)

Crushed ice

2 coffee cans, one at least one inch in diameter larger than the other

If desired, flavorings such as chocolate or fruit syrups or Kool-Aid powder may be added.

Preparation:

1. Mix the first four ingredients and stir well.

2. Place the smaller coffee can inside the larger can and put in enough ice, alternating with layers of rock salt two or three times, to completely pack the space between the two cans.

3. Tape or tie the lid down firmly on the smaller container.

4. Seal the larger can well and then roll it back and forth between two students for from 10 to 20 minutes, or one person can shake the can. You can also make drain holes in the bottom of the larger container, punching them with a nail, but it can be messy if the can will be passed back and forth.

5. To check for doneness, take off the lid and stir the mixture. If it is not frozen solid enough, drain the water caused by melting ice, repack and shake or roll again.