Stored Energy in Foods
The amount of energy stored in food usually is measured in calories. One calorie is defined as the amount of energy needed to raise the temperature of one gram of pure water (equivalent to one milliliter of water) one degree Celsius. The calories shown on most food labels actually are kilocalories (=1,000 calories). The word “Calorie,” when written with an upper case “C,” also denotes kilocalories.
When a carbon-containing molecule is burned (combustion), it consumes oxygen, produces carbon dioxide and water, and liberates energy (which can be felt as heat).
Since this activity involves an open flame, teachers may prefer to conduct it as a demonstration for the class. If students are performing the investigation in groups, the following safety guidelines from the Council of State Science Supervisors should be followed.
- Demonstrate the procedure before allowing students to replicate the activity. Look for possible hazards in the classroom. Alert students to potential dangers.
- Constant surveillance and supervision of student activities are essential.
- Smoke, carbon monoxide, and heat detectors are recommended in every laboratory. Units should be placed in the laboratory and related areas (storerooms, preparation rooms, closets, and offices).
- A positive student attitude toward safety is imperative. Students should not fear doing experiments, using reagents, or equipment, but should respect them for potential hazards. Students should read lab materials in advance, noting all cautions (written and oral).
- Teachers must set good safety examples when conducting demonstrations and experiments. They should model good lab safety techniques, such as wearing aprons and goggles.
- Rough play or mischief should not be permitted in science classrooms or labs.
- Closed-toe shoes are required for labs involving liquids, or heated or heavy items that may injure the feet.
- Confine long hair and loose clothing. Laboratory aprons should be worn.
- Proper eye protection devices must be worn by all persons engaged in supervising or observing science activities involving potential hazards to the eye.
- Give consideration to the National Science Teachers Association's recommendation to limit science classes to 24 students or less for safety.
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