Smoke in a Box

This experiment will show how oxygen is used up when something burns.

Equipment Needed

The Experiment

Find an empty shoebox or similar container that has a close fitting lid. Place two small cardboard tubes in position on the lid, as shown in Fig. 1, and draw a circle round them.

Cut around the outlines that you have drawn on the box lid. The two cardboard tubes should fit tightly into the two holes you have made for them. (Fig. 2)

Replace the lid. Light the end of a scrap of paper and then quickly blow the flame out.

Hold the now smoking piece of paper to the top of one of the cardboard tubes. Nothing should happen.

Now remove the lid and place a lighted candle stub in the bottom of the box, positioning the candle so that it burns immediately under one of the cardboard tubes (Fig. 3) when the lid is replaced.

This time, when a smoking piece of paper is held to the other chimney, as shown in Fig. 4, the smoke will be drawn down into the box and carried up and out through the second tube.

How does it work?

The burning candle quickly consumes all the oxygen in the box and draws in a further supply from the tube farthest away from it, sending the used warm air out through the tube immediately above it.

The smoke from the scrap of paper will also be drawn down into the box and will be seen to issue from the other cardboard tube immediately above the candle.