DIFFUSION AND OSMOSIS
Chapter 3 of your textbook explains diffusion and osmosis.
Diffusion is simply the net movement of atoms or molecules from a region of higher concentration to a region of lower concentration. The force behind the movement is heat or kinetic energy (also called Brownian motion). Diffusion occurs when you spill water on the carpet floor and it spreads out, or when you open a bottle of perfume and it leaves the bottle and spreads throughout the air in the room. Osmosis is a similar phenomenon that moves water from a region of high water concentration to a region of low water concentration. Imagine that a cell from your body is placed in a solution of water. If the concentration of the water inside the cell is the same as the concentration of water in the solution, then we describe the water solution as being “isotonic” or having the same concentration as the water inside the cell. In this case, net movement of water will be zero and the cell will not swell or shrink. In other words, the same amount of water will move in the cells as will move out. On the other hand, if the cell is placed in a solution of water that has a higher concentration (of water) compared to the concentration of water inside the cell, then osmosis will cause more water to move into the cell than will move out and this will cause the cell to swell. In this case, we say that the solution of water is “hypotonic”. Now imagine that the cell is placed in a solution of water that has a lower concentration (of water) compared to the concentration of water inside the cell. In this case osmosis will cause more water to move out of the cell than will move in the cell and the cell will shrink. In this case, we say that the solution is “hypertonic”. Learn more about osmosis and diffusion from Chapter 3 of your textbook. CELERY EXPERIMENT
We can place celery in three different water solutions to observe the effects of osmosis on the celery stalks. Salt will serve as our...
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