P2.1 - kinetic particle model of matter

Question 1

State the 3 states of matter and key properties

Answer 1

Solid - fixed shape, usually dense, difficult to compress, strong forces between molecules, vibrate in fixed positions in an ordered, regular pattern
Liquid - can flow/be poured from one container to another. Difficult to compress. Weak forces between molecules. Molecules move randomly but slowly; they stay close and collide more often than gases.
Gases - flow quickly and completely fill container. Easy to compress. Negligible forces between molecules. Gas particles have the highest kinetic energy. Move continuously, randomly and rapidly.

Question 2

State the name of the change from solid to gas and vice versa

Answer 2

1. Sublimation - solid to gas
2. Deposition - gas to solid

Question 3

What happens if we try to compress a solid?

Answer 3

The forces holding the particles in position become more repulsive, keeping the particles the same distance apart

Question 4

What happens when a gas is cooled?

Answer 4

Its particles slow down until they are close enough together and move slowly enough that forces can form between them. They join together and the material becomes a liquid.

Question 5

What is gas pressure?

Answer 5

The force exerted on the walls of a container caused by the gas particles colliding with the walls

Question 6

What is Brownian motion?

Answer 6

Evidence for movement of water particles. It is the random, zigzag, continuous motion of microscopic particles (e.g. pollen) that are pushed around by fast-moving, considerably smaller water molecules. The pollen and water particles collide with each other.

Question 7

What causes small particles of smoke to move around in a random pattern when observed under a microscope?

Answer 7

The smoke particles are being bumped into by very small but rapidly moving molecules in the air

Question 8

State and explain 2 factors affecting pressure

Answer 8

1. Temperature - as temperature increases, pressure also increases. In higher temperatures, particles have more kinetic energy so they move faster and therefore the collisions are harder and more frequent. Not directly proportional.
2. Volume - inversely proportional with pressure, as when it is decreased there are more collisions per unit area with the walls of the container because the distance the gas particles have to travel between collisions with the walls has decreased. Larger number of collisions per second.