Semi-permeable membrane and osmotic pressur

Level Elementary

Cells that make the body of the living thing are covered with semi-permeable membrane. There are so many tiny holes in semi-permeable membrane. A big particle like ugar is not passed though semi-permeable membrane, but a small particle like water can be passed. Only water moves to the salt solution when water and the salt solution are partitioned with semi-permeable membrane. This phenomenon is called osmosis. Moreover, the pressure takes at this time is called an osmotic pressure. The phenomenon of osmosis is confirmed by using familiar foods.

Experiment 1

Materials

sugar, salt, cabbage, and kitchen bowl (2)

The cabbage is shredded. Put it in two kitchen bowls dividing into the half.

Rub it by the hand without putting anything. It is confirmed whether

there is a change or not.

The salt is put to the cabbage and the sugar is put in another cabbage. They are often rubbed by the hand.

Either confirms whether a lot of water has come out. A lot of water comes out when the osmotic pressure is high.

The osmotic pressure of the salt is higher than that of sugar.

The osmotic pressure rises when a lot of solutes are dissolved.

The osmotic pressure becomes about 7times of atmospheric pressure by the salt solution

of 1%.

Science

Procedure

Concept