Solar Energy Science Projects

Absorb or Reflect?

What You Will Need:

• 2 clear glass pie plates or bowls
• 1 sheet of black construction paper
• 1 sheet of white construction paper
• 2 ice cubes
• A sunny spot outside

What To Do:

1. Place the sheets of black and white paper on a driveway or sidewalk in the sun. (The papers should not be touching each other. Your hand should fit in the space between them.) 
2. Set a pie plate on top of each sheet of paper and put an ice cube in the middle of each pie plate.
3. After 5 minutes, check on the ice cubes to see which one has melted the most.
4. If they haven't melted much, check again in 5 more minutes. Keep checking until the ice in one of the pie plates has completely melted. It could take more than 30 minutes for the ice to melt all the way, depending on how hot it is where you live.
5. Which ice cube melted faster - the one on the white paper or the black paper? Feel the sheets of paper. Which one feels warmest? Touch the dishes too, just be careful because the glass can get pretty hot!

What's Happening?

The ice in the dish with black paper under it should have melted first. Both pieces probably started to melt at about the same time, but the one on black probably melted completely into a puddle of water first. Why did it melt before the one on the white paper?

First you need to know that rays of light from the sun also bring heat - that's why it gets hot on a sunny summer day, why the paper and the dishes felt warm after being in the sun, and why the ice melted! Light and heat from the sun are called solar energy. Here's why the piece of ice in the black dish melted first: Ice melts when it gets warmer than freezing. White reflects light and heat, so most of the sun's rays (full of light and heat) bounced off of the white paper and it stayed cooler for longer. Black absorbs or soaks up light, sort of the same way a sponge soaks up water. It absorbed most of the sun's rays that hit it, making it get hotter faster. Look at the pictures to see how reflection and absorption work.

Glass also absorbs heat, so even if you had not put any paper under the dishes, the ice still would have melted from being in the hot sun in glass dishes. Both ice cubes probably would have finished melting at about the same time without the black or white paper, though. The black paper absorbed even more of the sun's energy (light and heat) than the glass dish, making the ice melt faster. The white paper reflected most of the sun's energy that hit it, keeping the dish and the ice in it cooler for longer so it took longer to melt. After the ice had melted, the paper and the dishes probably felt very warm (except for in the spot where the ice was keeping it cool). In fact, the dish on top of the black paper probably even felt hot when you touched it! Can you explain why? (Hint: it's the same reason that the ice melted!)

Sun Prints

You can make fun pictures by using the sun's power to make the color fade from construction paper! This project uses repositionable glue, which you can find in most stores that sell office or school supplies. (Elmer's and Scotch brands both make this type of glue.) You could also do the project by setting objects on your paper and laying it flat in the sun instead of using the special glue.

What You Will Need:

• dark colors of construction paper
• solid objects with interesting shapes that you can trace around (leaves, buttons, coins, and plastic toys work well)
• pencil
• scissors
• repositionable glue (Optional. Made by Elmer's or Scotch brands and available where office or school supplies are sold.)
• a window that gets lots of sunlight
• tape

What To Do:

1. Trace around your objects on construction paper and cut out each shape. Or, you can draw your own shapes and cut them out. Be creative! You could even draw letters to spell your name.
2. Arrange the paper shapes onto a new sheet of dark-colored construction paper to make a nice design.
3. Use the repositionable glue to stick each shape to your picture. Don't use much glue though, or it will be hard to peel your shapes off later.
4. Turn the shapes towards the window and tape the corners of your picture to the window to hold it in place.
5. Leave your picture in the window for a couple days or until you notice that the color of the construction paper has started to fade (compare it to a new piece of the same color of paper to see if it has changed).
6. When it is quite a bit lighter than it was when you started (it might take up to a week to get light enough; it depends on how many sunny days you have!), untape the picture from the window and peel off the shapes; they should come off pretty easily, just do it slowly to make sure your picture doesn't tear.

What's Happening?

Have you ever left an art project made from construction paper in the sun for too long? If so, you probably noticed that the color started to fade and the paper ended up a lot lighter than it once was. In this project, you covered parts of the paper with paper shapes, then when you left your picture in the sunlight, it started to fade. Since the shapes blocked sunlight from hitting the parts of the paper that they covered, you could see the original color of the paper after you peeled off the shapes! The extra layer of paper from the shapes protected those parts of the paper from the sun's rays that faded the color from the rest of the sheet of paper.

Sunlight contains ultraviolet (or UV) rays - the same rays that will give you a sunburn if you are in the sun for too long without sunscreen on. Those rays cause chemical reactions in the dye that gives construction paper its color. When the paper absorbs the rays of light, a chemical reaction breaks down the dyes so they aren't as bright. You can learn more about chemical reactions here. UV rays can lighten a lot of things. Some people's hair turns a lighter color when they are in a lot of sunlight. Hanging white laundry outside in the sun to dry can make it look whiter also.

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