Diffusion and Osmosis

Please take out your science journal to take notes in!

Cell membrane- selectively permeable, which means that some substances can pass through the membrane while others cannot.◦Think of the analogy- The cell membrane is like

a window screen, certain things can pass in and out of the screen (dust, pollen, rain, etc.) while other things are kept out (flies, bees, leaves, etc.).

The cell membrane- allows certain things to come into and out of the cell such as….◦IN

Oxygen, food, waterOUT Waste, Carbon Dioxide

All of these substances must pass through the cell membrane.

We call this movement – DIFFUSION◦Diffusion is the process by which molecules

move from an area of high concentration to an area of low concentration. The molecules spread out to fill the space.

Review of Yesterday's Experiment

What causes this to happen?◦Molecules are always moving. If there are a lot

of molecules in one area (high concentration) and they are all moving they will bump into one another and spread out (to low concentration) over time.

◦*Demonstration - air freshener

Diffusion in Daily Life1) When someone applies perfume or

deodorant, the smell slowly spreads into the entire room.

2) If the door of the kitchen is left open, the odor of food cooking spreads into the adjacent room.

3) The smell of a burning incense stick spreads throughout the room/house.

4) If a person is smoking in an enclosed area, its odor spreads in the area.

5) When a tea bag is kept in a hot cup of water, its color and aroma diffuses into the water.

Osmosis is the diffusion of water molecules through the cell membrane.

Water will move from an area of higher concentration to an area of lower concentration.

Concentration of water inside the cell is the same as outside.

High water concentration outside the cell – during osmosis, water moves into the cell.

Low water concentration outside of cell – during osmosis, water moves out of the cell.

Osmosis Video Gummy Bear Osmosis

Osmosis in Daily Life1) A patient with malfunctioning kidneys undergoes

dialysis which used the principle of osmosis to clear waste from the blood.

2) Rice or beans are soaked in water for a few hours before cooking as they take in water due to osmosis, become soft and hence take lesser time to cook.

3) Roots of plants take in water by the process of osmosis.

4) Osmosis is also used for preserving fruits and vegetables.

1) Osmosis is used to dehydrate the produce or pull the water out of it.

Osmosis vs Diffusion