How Sunlight Warms the Planet Lesson Plan
Science Experiment for Soil and Water Temperature Differences
May 6, 2009
Telling students about global warming and the effects of sunlight on the planet is important, but demonstrating how it works will make a more lasting impact. An easy classroom activity is to examine how dirt and water react to heat and cold. This can be performed as a class demonstration or with small groups as a science experiment. It can be used as an exploratory activity before introducing a concept such as thermal conductivity or how rising planetary temperatures affect the levels of carbon dioxide (CO2) in dirt or water based ecosystems.
Materials for the Experiment
- 2 small cups made of the same material, such as 2 paper cups or 2 kitchen glasses from the same set
- Room temperature water
- Room temperature dirt
- 2 thermometers
Procedure or Steps
- Allow the water and dirt to sit in the classroom for at least one day so they both are at room temperature.
- Fill one cup with water and the other with dirt.
- Place a thermometer in each cup and record the initial temperature.
- Remove the thermometers, and then place each cup in a freezer for 10 minutes. If a freezer is not available, place the cups in a cooler filled with ice.
- After 10 minutes, remove both cups from the freezer and place a thermometer in each cup. Record the temperature.
- Remove the thermometers, and then place both cups in full sunlight for 15 minutes. If direct sunlight is not available, place the cups under a heat lamp instead.
- After 15 minutes, replace the thermometers and record the temperatures.
Explanation of the Results
Initially the cups should have the same or similar temperatures. The time in the freezer simulates nighttime and the sunlight simulates daytime. In both cases, after being in the freezer and the sunlight, the soil should have the more dramatic change to colder or hotter when compared with water. This is because water takes much more energy to change its temperature than soil.
There is also a perception of temperature involved in this experiment due to thermal conductivity. Ask students to touch the soil and water when the two are at room temperature and record what they experience. Since room temperature is usually lower than body temperature and dirt is a poor conductor of energy it might feel that the dirt is actually warmer than the water.
This science experiment is not meant to be a stand alone activity. The differences in temperature reaction for soil and water can be useful for lessons about thermal conductivity and global warming. It can also be used to lead into a discussion about CO2 being retained in soil and water due to their planet-wide temperature increase.
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