It is easy to model the greenhouse effect. Take two soda bottles and cut off their tops. You will need two thermometers, masking tape, plastic wrap, scissors, colored pencils, graph paper, dark soil and a sunlamp. Cover the bulbs of the thermometers with cardboard to protect from direct heat. Add 2 cm soil to the bottom of each bottle. Tape a thermometer in each bottle, 2 inches from the top and above the soil surface. Record the temperature of the thermometer in your data table. That is your beginning temperature for each bottle. Next, place plastic wrap over one of the bottles. Tape it shut. The other bottle should be left uncovered. Place both bottles in direct sunlight or under a sunlamp. Measure the temperature every 15 minutes for 1 hour or longer if time permits and record the temperatures in the data table. This is a controlled experiment. Consider what the bottle with the plastic wrap represents and what the uncovered bottle represents! The data table should be time in minutes, versus temperature in degrees Celsius, for the covered and uncovered bottles. When graphing, the X axis is time in minutes and the Y axis is temperature in degrees C. You can graph the data for the covered bottle in one color-red, and the data for the uncovered bottle in a different color-blue. Analyze data for each bottle, graph the results and draw conclusions.