Observe the Greenhouse Effect in a Jar

This simple experiment serves as an introduction to the greenhouse effect. Your child will be able to see for himself how greenhouses work, and relate this understanding to what occurs in our atmosphere, as well as practicing key science skills such as observing and recording data, using a control, and drawing conclusions from results.

• 2 small thermometers
• 1 jar or other see-through container
• 1 clock or watch
• access to a sunny area to perform the experiment

1. Give your child the materials. Have him place the thermometers in direct sunlight.
2. Wait about three minutes so the thermometers will be giving accurate readings, and then have your child record the temperature readings of both, as well as the time, in an observation chart.
3. Your child should now place his jar over one of the thermometers, taking care that the jar does not cast a shadow over the uncovered one. If the thermometers are too large to remain horizontal inside the jars, it is fine to stand them against an inner side. Every minute, for ten minutes, he should record the readings of both thermometers on his observation chart.

The air over the exposed thermometer is constantly changing, and as it gets warm it is replaced by cooler air. Because the air in the jar cannot circulate to the rest of the room, this air stays in the sunlight and gets warmer and warmer.

A similar trapping of heat happens in the Earth's atmosphere. Sunlight passes through the atmosphere and warms the Earth's surface. The heat radiating from the surface is trapped by greenhouse gasses. Without an atmosphere, the Earth's temperature would average about 0F. This warming due to heat-trapping gasses is called the "Greenhouse Effect." Both the atmosphere and the jar allow light to enter, but then trap that energy when it is converted to heat. They work differently, however, because the jar keeps in the heated air, while the greenhouse gasses absorb radioactive heat.