1. Diffusion Osmosis Selective Transport1
There are three ways that materials can cross a membrane:
Diffusion
Osmosis
Selective Transport

2. of water affect the rate
Diffusion: 6
2. You drop food coloring into a glass of water. The dye is VERY concentrated at first at the top where the drop landed. The dye will spread to areas of LOWER concentration (clear). Eventually, the dye will spread evenly throughout the glass and the water will be one color.
Will the temperature
of water affect the rate
of diffusion?
1. One person farts in a classroom. A HIGH concentration of smelly molecules is found directly behind the person that farted. These smelly molecules will spread to areas of the room that don’t have fart molecules (LOW concentration). Eventually, the molecules will evenly fill the entire room. Usually, by then the molecules spread so far apart that you can no longer detect them. So, even though those people across the room cannot smell it, they will eventually still be breathing pieces of your fart.
Material will move from areas of HIGHER concentration to LOWER concentration.
How it works: Molecules are always moving. (remember temperature is the measure of their speed) They are also bumping into one another as they move. This causes them to bounce off each other and spread out. Eventually, they will spread evenly everywhere.
This works automatically without the use of energy.
Examples:

3. Which way will the Water
Osmosis:
Which way will the Water
move through Osmosis? 5
Osmosis is a special type of Diffusion. Osmosis is the diffusion of Water.
Water
This state of balance is called Equilibrium.
Water that has
20% Salt
Water that has
30% Salt
Water that has
10% Salt
Water that has
20% Salt
In osmosis, water will move from places with more water to places with less water.
Salt
Which way will the Salt
move through Diffusion?