Circulation of Hot and Cold Air

Equipment Needed

1 Warm Room
1 Candle

The Experiment

Open the door of a warm room a few inches. Hold a lighted candle near the top of the partly opened door.

You will be able to see from the flame that there is a current of air escaping from the room.

Hold the candle as low as possible at the door opening. You will see the candle flame move and feel a cold draft. This indicates that there is a current of cold air flowing into the room.

Finally, hold the candle about halfway between the top and bottom of the door. If you experiment with moving he candle around slightly, you should eventually find a spot where the flame burns steadily. This means that no air is moving in or out of the room this particular position.

How It Works

When a room is heated, the hot air rises and seeks to escape. This creates an area of low pressure at the bottom of the room. Cold air then enters the room at the bottom in order to equalize the pressure.