Did you know that different colors absorb different amounts of heat? Colors are NOT all equally heat absorbent. Think of walking out on the black tar in the summer time without shoes. Yowch! Walking on the sidewalk pavement or in the dirt is much easier on your bare toes! Why is that?
Let’s find out!
Why would anyone care what color their roof was? Well, take a look at the graph below.
When light interacts with an object, that light can be absorbed, reflected, or transmitted. Black objects absorb all wavelengths of light, while white objects reflect all visible wavelengths. They are complete opposites. Other colors absorb some wavelengths and reflect others, which is what makes them appear different to the human eye. Color is a result of the wavelength of light reflected by that object. For example, an object that absorbs selectively yellow light will not look yellow; it would be a combination of every other color besides yellow. The color you observe is a complement to the color the object absorbs. Take a look at the color wheel below.
If you observe violet, what color light is being absorbed?
When an object absorbs light, it usually converted from light energy to heat energy. This is what we are focusing on in our activity today!
Activity: How does color affect heat absorption?
YOU WILL NEED:
- 2 glasses
- Black construction paper
- White paper
- Tape or rubber bands
- A sunny day
Here’s what to do!
1. Find two identical glasses.
2. Cut black construction paper to the same height as one of the glasses.
3. Wrap the black construction paper around the glass so it covers the entire outside surface, as well as the top.
4. Tape the paper in place or put a rubber band around the glass to hold the paper in place.
5. Repeat steps 2-4 with the second glass with the white paper.
6. Fill both glasses with water. Make sure they have the same amount of water in them, and make sure you use the same temperature of water in both glasses.
7. Take the temperature of the water in each glass and write down the starting temperature.
8. Place both glasses outside in the sun.
9. Use the thermometer to take each glass’s temperature every 15 minutes for two hours. Carefully make a small hole in the paper at the edge of the glass to insert your thermometer.
10. Record your observations as you go. What did you notice?
11. When the two hours are up, create a line graph to track the temperature change in each glass. Temperature should be your Y-axis and time should be your X-axis. Did one glass heat up faster than the other? Did they both reach the same temperature at the end?
You should have found that the glass wrapped in black paper ended up with hotter water than the glass with white paper. This is because black absorbs more light (and thus, heat) than white. Clearly, black and white are on opposite ends of the color spectrum. Try using different colors to see how much of a difference there is between them.