KINETIC THEORY OF MATTER

What is meant by matter?

Matter is anything that has mass and occupies volume

List five points described in the kinetic theory of matter

1. All matter is made up of tiny particles – these particles can be atoms, ions or molecules 2. The particles have kinetic energy and are constantly in motion 3. The kinetic energy the particles have increases as temperature increases 4. The particles have spaces between them 5. There are forces of attraction and repulsion between the particles

What are the three states of matter?

1. Solids 2. Liquids 3. Gases

Compare solids, liquids and gases in terms of:

(i) The amount of energy the particles have

Solid: Particles have least amount of energy Liquid: Particles have more energy than in a solid Gas: Particles have most energy

(ii) The vibrations of and spacing between the particles

Solid: Particles vibrate in fixed position, very little space between particles Liquid: Particles vibrate more and are more widely spaced sliding past each other Gas: Particles vibrate most and are very widely spaced apart, moving independently

(iii) The attractive forces between the particles

Solid: Attractive forces between particles are strong Liquid: Attractive forces between particles are weaker than a solid Gas: Attractive forces between particles are very weak

Compare solids, liquids and gases in terms of:

(i) Volume

Solid: Definite volume Liquid: Definite volume Gas: No definite volume; will expand to fill its container’s volume

(ii) Shape

Solid: Definite shape Liquid: No definite shape; will flow into and take the shape of its container Gas: No definite shape; will flow into and take the shape of its container

(iii) Compressibility

Solid: Very difficult to compress Liquid: Difficult to compress Gas: Easy to compress

7i) What is meant by melting?

The process by which solid changes to a liquid

7ii) Describe the steps involved in a substance melting

1. The particles in the solid gain energy 2. Vibrations and motion of particles increases, attractive forces become weaker 3. Particles break further apart, substance becomes liquid

8i) What is meant by freezing?

The process by which a liquid changes to a solid

8ii) Describe the steps involved in a substance freezing

1. The particles in the liquid lose energy 2. Vibrations and motion of particles decreases, attractive forces become stronger 3. Particles brought closer together, substance becomes solid

9i) What is meant by vaporisation?

The process by which a liquid changes to a gas

9ii) Describe the steps involved in a substance vaporising

1. The particles in the liquid gain energy 2. Vibrations and motion of particles increases, attractive forces become weaker 3. Particles break further apart, substance becomes gas

10i) Distinguish between boiling and evaporation

Boiling: The changing of a liquid to a gas at the liquid’s boiling point Evaporation: The changing of a liquid to a gas below the liquid’s boiling point

10ii) What is the difference between boiling and evaporation in terms of the energy of the particles

During boiling, all of the particles in the liquid receive enough energy to break apart from each other. During evaporation, only the particles on the surface of the liquid receive enough energy to break apart from each other.

11i) What is meant by condensation?

The process by which a gas changes to a liquid

11ii) Describe the steps involved in a substance condensing

1. The particles in the gas lose energy 2. Vibrations and motion of particles decreases, attractive forces become stronger 3. Particles brought closer together, substance becomes liquid

12i) What two factors affect the state of a substance?

1. Temperature 2. Pressure

12ii) At atmospheric pressure, water is a solid below 0°C, liquid from 0°C to 100°C and a gas above 100°C. Explain why this is the case

Temperature determines the kinetic energy of the particles. Below 0°C particles have least energy (solid), from 0°C to 100°C particles have more energy (liquid), above 100°C particles have most energy (gas).

12iii) The diagram shows a deodorant can. The deodorant is a liquid inside the can but becomes a gas when sprayed outside. Explain how this can be the case despite the temperature being the same

Inside the can, the deodorant is under high pressure, forcing the particles closely together (liquid). When sprayed outside, the pressure is released, allowing the particles to spread apart (gas).

13i) What is meant by sublimation?

The process by which a solid changes directly to a gas

13ii) What is meant by deposition?

The process by which a gas changes directly to a solid

13iii) Give an example of a substance that at normal atmospheric pressure has no liquid state

Carbon dioxide

14i) What is Brownian motion?

Brownian motion is the random movement of microscopic particles in a fluid due to their collisions with the fluid’s particles

14ii) The diagram shows the result Robert Brown saw under the microscope of a pollen grain in a drop of water. Explain the random continuous motion observed by Brown as explained by Albert Einstein

The pollen grains were being moved by colliding with tiny water molecules that were in constant motion

14iii) Give two reasons why Brownian motion is evidence for the kinetic theory of matter

1. The pollen grains were being moved – evidence of tiny particles that can’t be seen (Part 1 of Kinetic Theory) 2. The pollen grains were being moved without ever stopping – evidence of the particles having kinetic energy and constantly in motion (Part 2 of Kinetic Theory)

14iv) If pollen grains were placed in a drop of ice-cold water, describe the difference in its motion. Explain your answer

The motion would be slower. The water particles have less kinetic energy and collide less often with the pollen.

15i) What is diffusion?

Diffusion is the movement of particles from an area of high concentration to an area of low concentration

15ii) The diagram shows an experiment set up to show diffusion.

(a) State what result is observed in this experiment once the tube is sealed?

A white ring forms in the glass tube

(b) Explain why this result is observed.

HCl and NH3 particles diffuse through the glass tube, meet and react forming ammonium chloride (NH4Cl)

(c) What evidence shows that HCl particles diffuse at a slower rate than the NH3?

The white ring of ammonium chloride forms closer to the cotton wool with the HCl

(d) Why does the result provide evidence for the kinetic theory of matter?

The HCl and NH3 gases reacting further down the test tube shows their particles are in motion

Give three limitations of the kinetic theory of matter

1. The kinetic theory of matter treats particles as tiny identical spheres – in reality different substances’ particles can have differences in shapes, sizes, bonding and structure 2. The forces of attraction or repulsion between particles are more complex than the kinetic theory of matter describes 3. The kinetic theory of matter suggests at a certain temperature all particles have the same amount of energy – this is not the case