Introduction

Have you heard of a greenhouse before? How about the Greenhouse Effect? Let’s investigate what effect a greenhouse has on temperature.

Note: A digital lab thermometer is best, but you can also use an oral thermometer or infrared noncontact forehead thermometer. Those thermometers may not display a temperature below about 90°F, but instead will just read “Lo.” That’s ok! You will still see a difference in temperature if there is one.

Experiment

To make sure that the water in each glass is at the same temperature initially, fill a large container with water. Pour one-half cup of water from the container into each glass, and measure the temperature of water in each, if possible. (See the note above.)

Carefully place one glass into the large zipper-lock bag and seal the bag. Put both glasses next to each other somewhere where they will receive direct sunlight. If the sunlight is from a window inside the house it may take several hours to get a readable temperature with a fever-type oral thermometer. For better results, place the glasses outside on a sunny day. You should get temperature readings in about 30 minutes. Check the temperature of the water in the glass that is NOT in the plastic bag every half hour until you get a reading. Once you do, measure the temperature of the water inside the plastic bag at the same time. Are the temperatures the same or different? 

What’s happening?

A greenhouse is made of glass or plastic that allows visible light to pass through it. Visible light travels in waves that are relatively short, which is why glass or plastic can’t stop them. What we feel as heat is a different kind of light that also travels in waves. Heat waves, also known as infrared light, are longer than the visible light waves that we can see with our eyes. Those longer heat waves cannot travel through glass or plastic in a greenhouse.

The walls of a greenhouse capture the Sun's heat, which keeps plants inside the greenhouse warm. Credit: NASA/ JPL-Caltech.

Visible light entering a greenhouse interacts with matter inside it, including air, water, soil, plants, etc. As matter absorbs visible light it heats up, releasing heat waves (infrared light). The longer infrared waves get trapped inside the greenhouse, which warms up as a result.

The Earth has a layer of gases in the air around it. (A good thing, as we depend on oxygen in the air to breathe!) Some gases in the air act like the glass or plastic of a greenhouse. They prevent infrared light (heat) waves from leaving the Earth, causing it to heat up. This is known as the Greenhouse Effect. You may have seen only a small temperature difference between the two glasses of water in the sun. All the extra

“greenhouse gases” that human activity releases into the Earth’s atmosphere also don’t cause a big temperature change, maybe one or two degrees. Even small temperature differences have a very large impact on our climate. That’s why it’s important to reduce the amount of greenhouse gases that humans release and to find ways to remove those gases from the atmosphere.

References

https://www.education.com/science-fair/article/ greenhouse-effect/

https://www.livescience.com/64825-why-earth-has-anatmosphere.html

https://climatekids.nasa.gov/greenhouse-effect/  

To view past “ChemShorts for Kids” activities, go to: 

https://chicagoacs.org/ChemShorts

 ―PAUL BRANDT