Section 3

1. Section 3 The Nature of Matter

2. A model of water dioxide A model of carbon dioxide Particle Theory of Matter • Matter is made up of extremely tiny particles. • These tiny particles may be molecules or ions. Molecules of the same substances are the same. Molecules of different substances are different.

3. Kinetic Theory of Matter • Gas particles are very far apart from each other. • They move at high speeds.

4. Kinetic Theory of Matter • Liquid particles are much closer. • They are moving continuously.

5. Kinetic Theory of Matter • Solid particles are close together in a regular pattern. • They cannot move from one place to another place. • Solid particles are vibrating about their positions all the time.

6. Experiment To show that ammonia molecules and hydrochloric acid molecules are moving. • Procedure • 1. Set up the apparatus as shown above. • 2. Leave the apparatus for some time and observe.

7. Experiment To show that ammonia molecules and hydrochloric acid molecules are moving. Result

8. To answer the questions on the next page, you must imagine that the gases are made of tiny particles

9. Ammonia solution White fume Hydrochloric acid Question What happens when the hydrochloric acid particles met the ammonia particles? Form white fume Are the particles of the two substances moving? yes Do they move at the same speed? No If the whole glass tube is warmed, do you think it takes a longer or shorter time for any change to be seen? It takes a shorter time to form the white fume because... Particles move faster at higher temperature

10. Ammonia solution White fume Hydrochloric acid The above experiment shows that both ammonia and hydrochloric acid diffuse.

11. The possible path of a gas particle Diffusion Diffusion is the spreading out of a substance. Particles of matter move from one place to other places. Why does diffusion occur? Is the rate of diffusion equal to the speed of moving particles? The speed of diffusion is much smaller Collision between the particles slows down diffusion rate. Why?

12. Experiment A Diffusion of bromine gas cover gas jar • Procedure • 1. Place 2 drops of bromine into the gas jar and cover it immediately. • 2. Observe how the bromine spreads by noting the colour. bromine liquid • Question • 1. How far has the bromine spread? • 2. Can you explain how the bromine diffuses (spreads)?

13. B. Diffusion of solid in liquid beaker water copper sulphate crystal • Procedure • 1. Place a copper sulphate crystal into 75 cm3 of cold water. • 2. Place another piece into the same volume of hot water. • 3. Leave the two beaker for about 20 minutes and observe.

14. B. Diffusion of solid in liquid • Question • 1. Why did we use a coloured solid? • 2. Had diffusion of the coloured solid particles occurred? • 3.Is diffusion faster in cold water or hot water? • 4. Is diffusion faster in a liquid or in gas? 1. We can observe the diffusion of a coloured matter. Yes Diffusion is faster in hot water Diffusion is faster in liquid

15. Change of States Gas Solid Liquid Example Steam Ice Water

16. Heat energy is given to solid particles which then move faster Heat energy is given to liquid particles which then move faster Heat energy is taken away from liquid particles which then move slower Heat energy is taken away from gas particles which then move slower Change of States: explained by kinetic theory Solid Liquid Liquid Gas

17. Go to section 3b