Question 10
**Solar-cooker investigation.** Work outdoors on a sunny day (a suitable heating device may be used instead). Materials: a pizza box, aluminium foil, two small plates, two of the same quantity of food to melt (such as chocolate or ice), long sticks, a stopwatch, black cardboard or black paper, plastic film, sticky tape, scissors or a cutter.
1. Open the pizza box. Cover all the inside walls and the inner part of the lid with aluminium foil.
2. Place a small plate with the food inside the box. Use sticks to keep the lid from closing. Move the lid back and forth until you have the correct angle for maximum reflection. Use the stick to hold the lid in position. Set the stopwatch and measure how long it takes for the food to start melting and then to fully melt.
3. Cover the bottom of the box with black cardboard. Place another plate with food to melt on top. Then, cover the box with plastic film, secure it with tape and place it in direct sunlight. Remember to adjust the lid so that the angle guarantees maximum reflection.
Was this a fair test? Explain your reasoning. If it wasn't, discuss why the conclusions drawn from this investigation might still be valid.
1. Open the pizza box. Cover all the inside walls and the inner part of the lid with aluminium foil.
2. Place a small plate with the food inside the box. Use sticks to keep the lid from closing. Move the lid back and forth until you have the correct angle for maximum reflection. Use the stick to hold the lid in position. Set the stopwatch and measure how long it takes for the food to start melting and then to fully melt.
3. Cover the bottom of the box with black cardboard. Place another plate with food to melt on top. Then, cover the box with plastic film, secure it with tape and place it in direct sunlight. Remember to adjust the lid so that the angle guarantees maximum reflection.
Was this a fair test? Explain your reasoning. If it wasn't, discuss why the conclusions drawn from this investigation might still be valid.
