Diffusion objectives Gases can move from one place

Diffusion

objectives Gases can move from one place to another on their own Know that this process is called diffusion and can be explained in terms of particles • Explain why the speed of diffusion can be changed by different temperatures. • Explain why diffusion is quicker in gases than in liquids.

Toast • Where does the smell come from? • How does the smell reach you?

answers • The smell starts in the corner of the room when the bread is cooked by the toaster • This makes a chemical reaction • The smell spreads through the air from one corner to the whole room (eventually) • Particles of gas carry the smell, moving through the air

What is diffusion? • It is a type of spreading of particles • It happens in solids, liquids and gases • But mainly in liquids and gases

Speed of diffusion • Is it fastest in solids, liquids or gases? • Why?

An experiment • You will find out how temperature affects the speed of diffusion • Draw the results of your experiment and write down what you have found out

What is the best statement? 1. 2. 3. 4. 5. 6. It was better in the hot water It was fastest in hot water The time was 10 s in hot water and 67 s in cold water so it was much quicker in hot water. The time was 10 in hot water and 1. 7 in cold water so it was much quicker in hot water because it diffuses quicker. It was quickest in hot water (10 s) than in cold water (67 s) because the particles are moving faster. It was quickest in hot water because the particles are moving faster and diffusing throughout the beaker. Cold water particles are moving more slowly and so don’t diffuse as fast. why?

What makes it better is. . • • Use of figures Use of units Use of scientific words Reasons why

Even better if • Record the temperature of the water

summary • Diffusion is spreading of particles • Fastest in gases because particles have more energy and are more free to move • Fastest in hot substances because particles have more energy too The end