Oxygen in air is a gas used by all the human beings and animals to breathe. About one-fifth (1/5) of the air is oxygen. That means about 21% of the air is oxygen.
Green plants release (give out) oxygen as a waste product in sunlight when they produce their food.
1) Put a waterweed in a beaker.
2) Put a funnel on the waterweed and a test tube full with water on it.
3) Keep it under the bright sun for about 30 minutes.
1) After 30 minutes you can see water in the test tube has gone down.
Reason: When oxygen is released, it will enter the test tube and the water will go down.
2) When the test tube is filled with oxygen you can insert (put in) a dimmed match.
Reason: If the test tube is really filled with oxygen the dimmed match should take fire again.
Green plants give out oxygen in sunlight.