1. The kinetic theory of matter states that all matter is made up of tiny particles called atoms and molecules that are in continuous random motion. 2. Brownian motion provides evidence for this theory by showing the random movement of small particles suspended in a fluid under a microscope. 3. The pressure exerted by a gas is caused by collisions of the gas molecules with the walls of their container, and increases when the temperature rises or volume decreases due to the more vigorous motion of the molecules.

1. Chapter 8 Kinetic Model of Matter Matter is made up of tiny particles called atoms and molecules. These particles are much too small to be seen by naked human eyes. How do we prove their existence?

2. contents States of Matter Brownian Motion Molecular Model of the Three States of Matter Effects of Temperature Pressure Exerted by a Gas Chapter Review

3. states of matter Solid Liquid Gas Fixed shape No fixed shape can flow take the shape of container No fixed shape can flow spread easily to fill any vessel take the shape of vessel Fixed volume Fixed volume No fixed volume take the volume of vessel Not compressible Not compressible Highly compressible Hard and rigid large force required to change its shape Definite surface No surface

4. The kinetic theory of matter states that all matter is made up of a large number of tiny atoms or molecules which are in continuous motion. kinetic molecular model of matter states of matter

5. brownian motion dotted lines represent the path of smoke particles between collision kinetic molecular model of matter Using a microscope, smoke particles can be seen moving continuously and haphazardly, as a result of being hit by unseen fast-moving air molecules. Brownian motion provides evidence for the kinetic molecular model of matter (kinetic theory of matter).

7. Brownian Motion Fig. shows a smoke cell and the erratic path followed by a particle of smoke. (continue on next slide)

8. Brownian Motion

9. Applets illustrating Brownian motion http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=41

10. Explain what causes Brownian motion When the air molecule collide with a smoke particle The molecules exert a force on the smoke particle Continuous random collisions produce a random resultant force on the smoke particle Cause the smoke particle to move randomly and continuously.

11. Why is a microscope necessary in order to observe Brownian motion? The points of light are too faint to be seen by an unaided eye The small size particles are too small to be seen with the naked eye.

12. Explain how Brownian motion provides evidence for the kinetic molecular model of matter Brownian motion is observed by suspending small sized particles in a fluid. Points of light are light scattered by the small-sized particles. The random, continuous and jerky movement of the smoke particles suggests that the small sized particles are continuously bombarded by random and continuously moving air particles or molecules.

13. brownian motion If heat is supplied, the motion of the smoke particles becomes more vigorous. The smaller the smoke particles, the more rapid is their motion. Diffusion is a result of Brownian motion. smoke particles moving continuously and haphazardly (irregular or random motion) diffusion

14. Diffusion is the spreading of molecules of their own accord without any external aid. Gas molecules move randomly all the time and they move into any available space. Hence they stay mixed and do not separate out. brownian motion diffusion Rate of diffusion depends on temperature of gases: higher temperature leads to faster diffusion density of gases: greater density leads to slower diffusion

15. diffusion in air brownian motion If bromine vapour is released into a similar space full of air bromine molecules keep hitting air molecules which get in the way bromine vapour spreads quickly throughout the space but much slower than in vacuum bromine vapour contained bromine vapour diffused vacuum

16. diffusion in liquid Diffusion also takes place in liquids, at a very much slower rate. copper(II) sulphate solution and water become uniformly mixed after a while due to diffusion lid water copper (II) sulphate solution copper (II) sulphate solution diffusion of copper (II) sulphate solution in water single uniform layer brownian motion

17. Why does diffusion occur? Because all molecules have spaces between them And the molecules have some form of random motion as stated in kinetic theory (all matter contains small atoms or molecules which are in random, continuous motion)

18. the molecular modes of the three states of matter molecular structure of a solid molecular structure of a liquid molecular structure of a gas molecular structure of solids, liquids and gases

19. the molecular modes of the three states of matter molecular structure of solids, liquids and gases Solid Liquid Gas Forces between molecules balanced forces which hold molecules in fixed positions forces as strong as those in solid molecules not held in fixed position, move among one another throughout liquid negligible only at moments of collision, the intermolecular forces act Distances between molecules arranged close together in a regular pattern not arranged in a regular pattern slightly further apart than in solid far apart mainly empty space between molecules

20. the molecular modes of the three states of matter molecular structure of solids, liquids and gases Solid Liquid Gas Motion of molecules vibrate about fixed positions alternately attracting and repelling one another vibrate to and fro alternately attracting and repelling one another move randomly with high speed, colliding with one another and with the walls of the containers Compress-ion cannot be compressed molecules are arranged close together little space between them cannot be compressed molecules are still close together little space between them can be easily compressed far apart mainly empty space between molecules

21. the molecular modes of the three states of matter molecular structure of solids, liquids and gases Solid Liquid Gas When heated molecules gain energy and vibrate more separation between molecules increases slightly (solid expands) molecules vibrate and move about more vigorously separation between molecules increases slightly (liquid expands) move even more randomly with higher speed, colliding with one another and with the walls of the containers (gas expands a lot)

22. Applets illustrating kinetic theory http://intro.chem.okstate.edu/1314F00/Laboratory/GLP.htm

23. effects of temperature As temperature increases, relationship between the motion of molecules and temperature surrounding air particles move faster and hit the particles move frequently and harder Brownian motion of the smoke particles in the air becomes more vigorous thermal energy is transferred to the molecules and the molecules gain kinetic energy causing molecules to move faster

24. The pressure of a gas is causes by collisions of the molecules with the walls of the container. The magnitude of the pressure is related to how hard and how often the molecules strike the wall. The "hardness" of the impact of the molecules with the wall will be related to the velocity of the molecules times the mass of the molecules. pressure exerted by a gas

25. pressure exerted by a gas Pressure exerted by gas molecules increases due to: relationship between the motion of molecules and pressure a decrease in volume of a container, or (and) an increase in temperature

26. pressure exerted by a gas pressure of a gas in terms of motion of its molecules 1. Number of gas molecules per cm 3 doubles half the volume of container 2. Number of collisions of molecules with the wall in one second doubles 3. Pressure doubles 1. Molecules move faster temperature of gas in container increases 2. Molecules hit the walls more frequently and more violently (with greater force) 3. Pressure increases

27. Relationship between Pressure, volume and Temperature

28. Questions A syringe contains 80cm 3 of trapped air at room temperature. The piston is slowly pushed inwards, compressing the air. Some information about the air inside the syringe is given in the table below. Calculate the pressure P of the air after compression. Before compression After compression Volume of air 80 cm 3 20 cm 3 Temperature of air 25  C 25  C Pressure of air 1.0 x 10 5 Pa P

29. Questions The volume of air in the pump at the start of the stroke is 20 cm 3 , and the pressure of the air is 1.00 x 10 5 Pa. Calculate the pressure when the volume has been reduced to 8 cm 3 , assuming that no air has escaped from the pump and the temperature of the air is constant.

30. Matter Solid Gas (a) Properties of solids, liquids and gases (b) Relationship between the motion of molecules and temperature (c) Pressure of a gas Liquid Brownian motion diffusion Kinetic theory of matter is based on evidence like consists of are discussed in used to explain