Energy Content of Food
Grade Level: 7th - 8th; Type: Physical Science
Construct a calorimeter and determine the caloric value of a sample of foods.
- What is a calorie? How does it differ from a Calorie?
- What is a calorimeter?
- Why is it important to determine the caloric values of different foods?
- How is the energy in food released by the human body?
- How many calories should a normal individual, age 16, consume in one day?
- Why are we currently confronted with an obesity problem?
- What measures might the government take to stem the obesity problem/
- What foods tend to be very high in calories?
- What kinds of foods tend to be low in calories?
- What part does or should exercise play in this scenario?
In this day and age we are all concerned with calories. A calorie is a unit used to measure heat. One calorie is the amount of heat needed to raise the temperature of 1g of water 1 degree C. The term calorie comes from the word caloric. In the 1700s, scientists thought that heat was an invisible substance and they named it caloric. Today we know better.
A device called the calorimeter was invented to measure the amount of heat given off when a substance is burned. We still use a calorimeter. In this project, the student will construct a simple calorimeter to capture the energy released by the burning of food. Basically we all require energy in order to live. We obtain this energy from food. If we to trace the food back, it takes us to photosynthesis, a process by which green plants capture the sun`s energy, transforming it into chemical energy that is stored in the chemical structures of molecules. We eat the food. We oxidize and digest the food and in the process release and recover the stored energy. Thus, indirectly, we are using the sun`s energy.
In this project the student will learn how to measure how much energy is stored in different types of food. What will be measured is the amount of heat released in the process of burning different foods. Your calorimeter has a reservoir of water. When the heat of the burning food is released it serves to heat the water in the reservoir in the calorimeter. You will measure the temperature of the water before and after the burning of specific foods.
The increase in the temperature (Degrees C) times the mass of water in grams will tell us the amount of energy we obtained in the calorimeter in calorie units. We use the formula Q of water =mc times change in temperature. Note: Q of water is the heat captured in calories, m is the mass of water in grams, c is the specific heat capacity of water namely 1cal/g per degree Celsius and ^T is the amount of change in temperature in degrees C.
- 2 aluminum or metal soda cans (one small, one large)
- Thermometer (centigrade),
- Large graduated cylinder,
- Large paper clip ,
- Balance ,
- Calculator ,
- Food samples (such as small squares of bread, cheese, banana ,tomato, and lettuce)
These materials may be borrowed from the school science lab and the rest purchased from the local super market.