Put five inches of potting soil in two aquariums.
Fill two aquariums with five inches of water. Put one inch of crushed plastic foam over each water-filled aquarium.
Tape two thermometers to the side in each aquarium so that they can be read from the outside. Place one above the water/foam or soil level and the other 3 inches below the surface. Place only one thermometer in each empty aquarium.
Put the lid on one air-filled, one soil-filled and one water-filled aquarium.
Put the remaining lid mostly over one empty aquarium and fill the aquarium with CO2. You can make your own CO2 by mixing baking soda and vinegar in a plastic bottle or balloon and expelling the gas into the aquarium -- cover the aquarium immediately after adding the CO2 gas.
You can also use a piece of dry ice to release CO2 gas. Drop the dry ice into the aquarium, cover the aquarium and allow the dry ice to sublime. When the temperatures equalize in the two "empty" containers, take their baseline temperature.
Position a light over each of the six aquariums so that the light is the same distance above each aquarium and centrally placed. Alternatively, place the air-filled and gas-filled aquariums in the sun so that they are equally exposed to sunlight. If using lights to heat the last two aquariums, turn the lights off at night and back on in the morning.
Record the temperature on the thermometers before turning on the light. Turn on the light and record the temperature from all thermometers every minute for 15 minutes. Do this only for the soil- or water-filled aquariums.
Turn off the lights. Record the temperature every minute for 15 minutes on all eight thermometers in the soil- or water-filled aquariums.
Graph the temperature results of the four water- or soil-filled aquariums separately, and then overlaying each other but color coded on one graph.
Record the temperature of the air-filled and gas-filled aquariums at the same time daily -- late afternoon would be optimal. The next week, graph the temperatures of the air-filled and gas-filled aquariums and compare the results with the graph of the water-filled and soil-filled aquariums.