Cold Frames

• A cold frame is essentially a small version of a greenhouse. Rather than constructing an entire building, a cold frame is a small box that is placed on the ground to capture sunlight. It only requires a square or rectangle of wood and a glass window to place over the top. Ideally, a cold frame faces south and is inclined at a 10 percent angle. There are many experiments that could be conducted with a cold frame, such as determining what kinds of plants grow well inside of one and why.
  
  

Soda Bottle Greenhouses

• Different substances have different abilities to absorb or reflect heat; the color of a substance is important, as well. A soda bottle can be used as a small greenhouse. Try putting a different material inside of soda bottles, like potting soil, white stones, water, peat, or other materials to see which ones absorb or reflect heat best. The bottles must all be the same color, preferably clear, to not add an additional variable to the experiment. Tape a thermometer to the inside of the bottle, not touching the experimental material, and cap the bottle. Put the bottles under a consistent light source, like a strong lamp or good sunlight, and measure the temperature of each bottle at regular intervals. Students can make a prediction about which bottle they think will get hottest and why, and learn more about heat absorption through this experiment.
  
  

Greenhouse in a Jar

• The Greenhouse Effect, named such as it resembles the effects found within an actual greenhouse, is of great interest in science because if greenhouse gases trap in too much heat, the temperature of the earth can rise. But greenhouse gases also keep the earth at a comfortable temperature. You can make a mini model of how the greenhouse effect works with a jar. Place a jar over the top of a thermometer and put both in the sun or under a sunlamp. Put another thermometer nearby so that it is in the same amount of light. Take readings of both thermometers at regular intervals. How do they compare? Why is it getting so hot inside of the jar?
  
  

Light and Plant Growth

• You can use a greenhouse to study plant growth. Set up a cold frame and plant some seedlings, like beans, both inside and outside the cold frame so that they are in equal sun. Measure the growth of the seedlings every day for a few weeks and compare the growth of the seedlings inside and outside the frame. This experiment is best done in the spring or summer, when the plants outside the box can survive. You can also use two cold frames and compare growth rates between the two - put one in full sun and one in partial sun, or put a dark covering on the ground in one and a light covering on the other.