Ah...I see, diffusion! Diffusion means the net movement of substances from an area of higher concentration to an area of lower concentration. The substances are just like bouncing balls which keep bouncing forever. When they are put in one room with the door closed, they only bounce in that room. However, when the door is opened, the balls immediately go to the room with fewer balls because they do not need to squeeze with one another. They can have more space. This is an example of diffusion. And I now understand that the balls do not need energy to diffuse through the room.
Osmosis is also a type of passive transport. It is the diffusion of water through the cell membrane. As I indicated in the last sentence, the action is passive because osmosis is a kind of diffusion. Have problem understanding osmosis? No problem! The demonstration in class makes us all understand better. Some girls in class act as the cell membrane and some boys act as the water molecules. The boys move randomly around the girls, just like water molecules moving around the cell membrane. When Mr. Olson said 'stop', the number of boys on each side were always nearly the same. It shows that water molecules diffuse through the cell membrane until the state of equilibrium is reached. After that, Mr. Olson used chairs to represent salt. When he pulled out a chair, one boy would sit on it, just like water molecule attracting to salt. As chairs were pulled out on only one side of the cell membrane, there were fewer boys moving around on that side. Other boys then went to that side to fill in the space. As a result, there would be more water molecules on the side with salt.
This activity was really interesting and it let us move around during the lesson.
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