Experience. Algae release oxygen in the light.
Take a glass filled with water.
We place the shoot of the aquatic plant Elodea in the water with a cut upwards, cover it with a funnel, on which we put a test tube.
Now we put the glass in a bright light.
In the light, in a glass, Elodea emits gas bubbles.
We carefully remove the test tube filled with gas, closing its hole with your finger.
Let’s put a smoldering torch into the test tubes. It lights up with a bright flame.
This means that oxygen has appeared in this test tube (only this gas supports combustion).
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.