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Science Lab Experiment: Oxygen in Air

Demonstration: Oxygen in Air

Object: To determine whether oxygen forms part of air.

Materials: flask, matches, candle, food colouring, water, large beaker, water


Method: Materials were set up as shown in the diagram. Tongs were used to lower the lighted candle into the large beaker. Food colouring was added to the water in the beaker.

Observations: It was seen that water entered the flask, as it was lowered over the burning candle. As the candle burned, more water entered the flask. When the candle flame extinguished, water was seen to enter the flask by about 1/5th of the total volume. .

Conclusions: It was concluded that since oxygen is required for burning, the oxygen was used up by the burning candle and water rushed in to replace this air. Therefore, oxygen makes up about 20% or 1/5th air.