Math & Science Gumbo

The Homemade Ice Cream Challenge

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

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 and make ice cream.

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.

Converting temperature – use the following temperatures for practice

Celsius Temperature	Fahrenheit Temperature
	75 F
9 C
	60 F
37 C
	125 F
99 C

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

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)	Ingredients x 3
1 tablespoon sugar
1/2 teaspoon vanilla
1/2 cup milk

The Homemade Ice Cream Challenge (PDF)