Chapter 2: Kinetic Particle Theory

Question 1

What is the arrangement, movement and forces of attraction of solid particles?

Answer 1

Arrangement: Very closely packed in an orderly manner.
Movement: Vibrate about fixed positions
FOA: Very strong

Question 2

What is the arrangement, movement and forces of attraction of liquid particles?

Answer 2

Arrangement: Closely packed in a disorderly arrangement
Movement: Slide over each other
FOA: Strong

Question 3

What is the arrangement, movement and forces of attraction of gas particles?

Answer 3

Arrangement: Far apart in a disorderly arrangement
Movement: Move about rapidly in all directions
FOA: Weak

Question 4

What are the different processes that matter can go under?

Answer 4

1. Melting
2. Boiling
3. Sublimation
4. Condensation
5. Freezing
6. Deposition

Question 5

What are the properties of a liquid?

Answer 5

1. Fixed volume
2. No fixed shape

Question 6

What are the properties of gas?

Answer 6

1. No fixed volume
2. No fixed shape

Question 6

Why can both liquids and gases take up the shape of a container, but only a gas can fill the container?

Answer 6

1. Liquid particles can slide past one another, thus the particles can move to occupy the shape of the container.
2. Gas particles are far apart and move in all directions, thus they can take up the shape of the container
3. Gas can also move apart as it is held by weak forces of attraction, to fill up the container.
4. Liquid particles are closely packed and cannot move apart as it is held by strong forces of attraction, thus they cannot fill up the container.

Question 7

Why do gases have the ability to be compressed?

Answer 7

1. Gas particles are far apart.
2. When a force is applied to compress it, the particles have space to move closer together and thus, its volume decreases.

Question 8

Why do equal volumes of solid substances and gaseous substances have different masses?

Answer 8

1. Density is the amount of mass per unit volume.
2. Solid substances have more particles per unit volume, resulting in them having more mass per unit volume, thus solid substances have a higher density than gaseous substances of the same volume.

Question 9

Why is ice floating on top of water unsual?

Answer 9

Using kinetic particle theory, solids usually have a density higher than liquids as solid particles are very closely packed. Thus we would expect ice to sink in water but it instead floats.

Question 10

Explain, using Kinetic Particle Theory, the changes occuring when ice melts into water.

Answer 10

When ice is heated, its temperature increases, and its kinetic energy increases as well.
2. Solid particles gain heat, causing them to gain more kinetic energy.
3. Their volume increases, particles gain heat and vibrate about their fixed positions more vigourously.
4. They will eventually gain enough energy to overcome the very strong forces of attraction between the solid particles, where particles change from being very closely packed in an orderly manner to a closely packed and disorderly manner.
5. Thus, ice melts to form water.

Question 11

Why does the temperature remain constant when water is being boiled?

Answer 11

1. All the heat energy absorbed is used to weaken the strong forces of attraction between the water particles.
2. After gaining enough energy to overcome the strong forces of attraction between the water particles, particles change from sliding past one another to moving about rapidly in all directions.
3. Particles then change from being closely packed in a disorderly manner to being far apart in a disorderly manner.

Question 11

Define ‘diffusion’

Answer 11

The random movement of particles in all directions to fill up any available space.

Question 12

Why do oxygen and bromine eventually spread out evenly when confined in a container?

Answer 12

1. Diffusion occured
2. The particles of air and bromine move in all directions to fill up any available space.
3. The particles will diffuse into the spaces between each other until a homogenous mixture of oxygen and bromine is formed.

Question 13

What are the factors affecting the rate of diffusion?

Answer 13

1. Relative molecular mass
2. Temperature

Question 14

How does relative molecular mass affect the rate of diffusion?

Answer 14

The higher the relative molecular mass, the slower the rate of diffusion.

Question 14

How does temperature affect the rate of diffusion?

Answer 14

The higher the temperature, the higher the rate of diffusion.

Question 15

Explain why the level of the coloured liquid in the tube connected to the porous pot when it contains air and is surrounded by air stays the same.

Answer 15

1. There is air inside and outside of the porous pot so the rate of diffusion of air into the pot is the same as the diffusion of air out of the pot.
2. The pressure inside and outside the pot is the same so the coloured liquid is at the same level on each side of the tube.

Question 15

Explain why the level of the coloured liquid in the tube connected to the porous pot when it contains air and is surrounded by hydrogen is higher on one side and lower on the other.

Answer 15

1. The relative molecular mass of hydrogen is lower than that of air.
2. The rate of diffusion of hydrogen into the porous pot is faster than that of air.
3. The pressure inside the porous pot increases as hydrogen enters and takes up space.
4. Air is pushed down into the tube, pushing the liquid in the tube down.
5. Thus, the level of the liquid below the porous pot drops, while the level of the liquid on the other side rises.

Question 16

Explain the change in density between ice and water

Answer 16

The density of water decreases when water freezes at 0 degree Celsius. The arrangement of water molecules change to become further apart after freezing. Thus there are fewer particles per unit volume in ice, and density of ice is lower than water.