Energy from the sun doesn’t just warm us, it can also create chemical changes. Photosensitive paper (solar print paper or the like) is coated with a chemical that changes color when it’s exposed to certain wavelengths in sunlight. See how blocking the sun’s light can stop those changes from happening!
How can sunlight create chemical changes?
- Direct sunlight 3-5 small objects
- Sheet of photosensitive paper
- Timer or clock
- Tub or large pan of water
- Collect between three and five small objects. Ones that are heavy for their size will be less likely to be blown around if you’re doing this outdoors. It’s also interesting if at least one of the objects is transparent or translucent.
- Pull the piece of photosensitive paper out of its package, set it in the sun blue side up, and quickly arrange your objects on it.
- Leave the paper undisturbed for two minutes. It should be pale blue at this point; if not, go ahead and leave it a little while longer, but be careful not to leave it too long.
- Take the objects off of the paper and dunk it in the tub of water. Leave it in there for one minute to wash the chemicals off, then take it out and hang it up or lay it flat to dry.
- Observe the paper. Can you see silhouettes (flat shapes like shadows) of the objects that you put on the paper earlier? If you used a translucent or transparent object, is the silhouette sharper or fuzzier? Anywhere the sunlight touched the paper should be solid blue; anywhere where an object blocked the sun’s rays and kept them from affecting the chemical on the paper should be white.