This practical involves students constructing a solar powered oven from a pizza box and some foil. If placed in direct sunlight for half an hour or so, the temperature within can rise to around 135°C. Obviously it is best to pick a very hot day to conduct the test part of the practical although the construction may take place some time before.
Equipment typically required (per set):
Pizza boxes may be provided by a friendly and generous local pizza store. If this is not possible they can be constructed from sturdy cardboard.
- large cardboard pizza box
- Aluminium foil
- Sticky tape
- Felt-tip pen
- Black paper (sugar paper works well)
- Sheet of clear Perspex or polycarbonate (fairly sturdy)
Your technology department may be able to provide you with the plastic sheet. If not, hardware stores sell polycarbonate sheets which will need to be cut to shape.
Students firstly draw a 3-4cm border on the top of the box and cut three of the four lines of the inner square, making a flap. A piece of the foil is cut and glued to the bottom face of this flap. This will act like a mirror, focussing the heat from the sun into the box. The inside of the box should be lined with more foil and then black paper should be taped on top. The black paper layer will absorb heat and the foil layer will keep that heat inside. The sheet of plastic should be taped across the flap opening, making sure that the seal is as airtight as possible.
An egg is broken and placed into a saucer. The oven can be opened using the original pizza box opening, and the saucer can be placed inside. The oven will take around half an hour to reach a high enough temperature to cook the egg but it will need to be placed in direct sunlight with the top flap directing the sunlight into the box.
The plastic layer works like a greenhouse, trapping the heat inside the oven.
Estimated technician preparation time (assuming the pizza boxes and plastic sheet have been collected) 10-15 mins.