Kinetic Theory

1. Kinetic Theory • All matter is made up of particles, called molecules. • They are constantly in motion. • When they are close together, the molecules attract each other strongly. • When they are far apart, they hardly attract each other.

5. Solids • The particles are close together. • They are held together by strong forces. • They vibrate to and fro, but cannot change positions. • They have a fixed volume and shape.

6. Liquid • The particles are close together. • They vibrate so vigorously that the forces can no longer hold them in fixed position. • They have a fixed volume but no fixed shape.

7. Gas • The particles are very far apart and hardly attract each other. • They move at random at very high speeds. • They have no fixed volume and shape.

8. Smoke particle

9. Smoke Particle

10. Brownian Motion • A smoke particle is bombarded by millions of air molecules around it. • The bombardment comes from all sides but not in equal number. • Brownian motion provides evidence for particle motion. • This can be explained by using the kinetic theory.

12. Air Particle Smoke particle

13. Air Particle Smoke particle

14. Brownian Motion

17.    Ans: E

18. Very Good!

19.     Ans: B

20.      Ans: E

21. Kinetic theory Model (3 Dimensional model)

22. Pressure of Gas Gas molecules Volume of Gas Volume of Gas Temperature of Gas

23. Kinetic theory and Boyle’s Law • When a gas is compressed, • the molecules have less volume to move in. • They hit the walls more often and so produce a greater pressure.

24. Kinetic theory and Charles’ Law • As temperature rises, the molecules move faster and hit the walls more often. • If the pressure is to remain constant, the volume must increase.

25. Kinetic theory and Pressure Law • As temperature rises, the molecules move faster. • When the volume is fixed, the molecules hit the walls more often. • This increases the pressure.