Science Buddies: "Ask an Expert"

Hello. This will be a very lengthy post, unfortunately. I used this project (https://www.sciencebuddies.org/science- ... n-of-light.), as my science fair project for my local school. I have advanced to the city-wide level, and I am looking to preform my experiment a second time. However, there is one problem. My results & data did not have any noticeable pattern or trends that would prove or disprove my hypothesis. I may be misinterpreting the data, or there may be a problem with my methodology. To summarize, my project involved shining a heat lamp on a mason jar filled with water and wrapped in colored paper, and measuring the temperature to see how color affects it.

Underneath I will copy and paste a summarized version of my project report to give the proper context.

Purpose:
How does the color of a material affect its absorption of light, as measured by the thermal energy of an object?

Hypothesis:
White will have the lowest average heat, red will have an increased average, followed by orange, yellow, green, blue (or cyan), indigo (or blue), violet, and finally, with black having the highest average temperature.

Abstract: This experiment was designed as a way to measure the light absorption of a colored material. It was performed by shining a heat lamp close to a jar filled with water, which had colored paper wrapped around it, and measuring the temperature after exposure for a period of time. The results were inconsistent with my hypothesis, though not altogether disproving my hypothesis either. White had the highest average temperature recorded after exposure, and the lowest average temperature recorded was orange.

Background Research:
Light, as a wave, can have different wavelengths, and one part of its full spectrum is visible light, which has shorter wavelengths than infrared, and longer ones than ultraviolet. However, even within visible light, the colors we perceive are longer and shorter subsets of visible light, selectively reflected and absorbed by objects. When an object absorbs light, it is converted to another type of energy, usually thermal. Because of this, the color of a material affects its temperature when absorbing light. This is the basis of my experiment.

Materials:
Astrobright Colored Paper, Heat Lamp & Base, 8 Mason Jars, Hammer & Nail, Play-Doh, Ruler, Blue Spirit-Filled Partial Immersion Thermometer

Methodology:
To set up the project:
Step 1. Use the hammer and nail to put a hole in each jar’s lid.
Step 2. Screw the heat lamp into the base.
To perform the project:
Step 1. Fill the jar with 400 milliliters of water; then get the water temperature to 25 degrees Celsius. Step 3. Place in the thermometer, and seal excess space with play-doh. Step 4. Place the jar 5 centimeters from the heat lamp. Step 4. Set a timer for 20 minutes; Turn on the heat lamp, and wait. Record the temperature of the water after time has elapsed.
Repeat these steps for every color and perform three trials for each.

Data:
White: 30 degrees Celsius/29 degrees Celsius/29 degrees Celsius
Red: 28/27/30
Orange: 26/26/28
Yellow: 27/28/27
Green: 28/28/28
Blue: 30/28/29
Indigo: 28/27/29
Violet: 28/28/28
Black: 28/28/30

Thank you in advance for anyone kind enough to help.

Hi - I searched our forum and found some other posts were students had trouble with this project, for example this one: viewtopic.php?t=15655

A few questions/thoughts based on those posts and what you've written:

1. Are you using an actual heat lamp bulb and not just a regular incandescent bulb?
2. Are you wrapping the construction paper as tightly as possible around each jar? Glass is not a very good conductor of heat to begin with, and if there's an air gap because the paper isn't tight, that will add more insulation, making it harder for the heat from the paper to transfer to the water.
3. Are there any other light sources that could be affecting your experiment, like light from a window?
4. 5 centimeters is pretty close to the heat lamp, and some heat lamps are pretty large. I see the project recommends 15-20cm. You need to make sure the heat lamp is aimed directly at the side of the jar, not "over" the jar.
5. If you run each trial for a longer time, does the temperature keep rising? You can test this with a single color first to find out. You might see more of a difference in the final temperatures if you run the experiment for longer.

Another, alternative option (although I'm not sure how much you are allowed to change your experiment) would be to skip the jars of water entirely, and use an infrared thermometer to measure the surface temperature of the sheets of paper directly. You would want to stand the pieces of paper up somehow, because if you lay them flat on a table and aim the heat lamp down at them, the table surface below them will start to heat, and that would affect subsequent trials.

Hope all of that helps, please write back if you have more questions or to let us know how it goes.

-Ben

*another option I just thought of is to use metal cans instead of glass jars, since metal is a much better conductor of heat.