A Solar Oven
You can do this all by yourself! It's one of the best food science fair projects because you are able to learn a concept then eat the food at the end!
1 large box with a lid (Some people use pizza boxes, and this usually works. Wooden boxes will last longer though.)
clear plastic (The kind you use to wrap books.)
black construction paper
instant brownie mix
Pyrex baking dish
Using your ruler and pencil, measure two inches inward from every side of the box, and mark the square you make. You should have a square that is within the lid.
Using a cutter (if it's a wooden box, ask for your parent's help using a saw), cut out three sides of the square you marked off. One side should still be connected. You have now created a flap on the lid.
On the inner side of the flap and using glue, stick a piece of aluminum foil that will cover the entire inner flap. Make sure the aluminum foil is as flat and as smooth as possible.
Remove the lid from the box. Glue the clear plastic sheet onto the inside of the lid. Make sure the plastic sheet is relatively tight over the opening. When the lid is right side up, and you raise the flap, the tight plastic sheet should be stuck to where the opening is.
Inside the box, at the bottom, glue another flat and smooth sheet of aluminum foil. When you've done this, cover the aluminum foil with black construction paper, making sure this is also glue snugly to the bottom of the box.
Put the lid back on the box and raise the flap, holding it up with a stick. Face this towards the sun, making sure that the sun is hitting the aluminum foil of the flap and it is bouncing its light through the plastic sheet and into the box. Wait half an hour.
Use the half hour waiting time to mix yourself a batch of brownies, and lay these brownies out on a Pyrex baking dish.
Go back to your box and remove the lid, placing the baking dish inside. Replace the lid, and again lift the flap and secure the stick.
Make sure the box is again facing the sun, where the sun is hitting the aluminum foil at maximum and bouncing the light into the box.
Check the cooking time of your brownies, and wait twice as long for your oven to cook it. So if the brownie mix box said it takes 10 minutes to bake, wait 20 minutes.
Food science fair projects are usually a lot of fun, and this solar oven is no exception. Just remember that solar ovens take twice as long to cook anything, and they must be preheated for at least half an hour before cooking. The heat from the sun, uses convection to diffuse heat all around the oven, and this heat is what gets transferred into the brownies which is what bakes it!