Topic 3- Particle Model of Matter

Question 1

What is the definition for density? state units

Answer 1

• the mass per unit of a material

- density kg/m^3, mass kg, volume m^3

Question 2

Describe the particle arrangement of a solid

Answer 2

tightly packed in a regular arrangement.

particles can only vibrate on the spot

Question 3

Describe the particle arrangement of a liquid

Answer 3

close together but with an irregular arrangement. they can flow over each other

Question 4

describe the particle arrangement for a gas

Answer 4

particles can move freely, separated with no arrangement

Question 5

what is always conserved when a substance undergoes a change of state?

Answer 5

mass

Question 6

How does a change of state differ from a chemical reaction?

Answer 6

In a change of state, the material can return to having its previous properties if the change is reversed.

Question 7

What is sublimation?

Answer 7

when a solid changes into a gas without passing through a liquid state

Question 8

describe the motion of molecules in a gas

Answer 8

they are in a constant random motions

Question 9

what factors affect the average kinetic energy of gas molecules?

Answer 9

• temperature of the substance

- the higher the temperature, the higher the average kinetic energy of the gas molecules

Question 10

Why does pressure increase as temperature increases?

Answer 10

• kinetic energy of molecules increase
• collisions between molecules become more frequent
• greater rate of change of momentum
• greater force and therefore pressure

Question 11

describe the force that the pressure exerts on the walls of a container

Answer 11

• the net force acts as right angles to the containers surface
• force increases as pressure does too

Question 12

explain how increasing the volume of a gas in a container decreases the pressure

Answer 12

• molecules become more spread out so time between collisions increases
• rate of change of momentum decreases, so force exerting on container decreases, resulting in low pressure.

The reduction in the volume of the gas means that the molecules are striking the walls more often increasing the pressure, and conversely if the volume increases, the distance the molecules must travel to strike the walls increases and they hit the walls less often thus decreasing the pressure.

Question 13

unit used for pressure

Answer 13

pascal (pa)

Question 14

What increases when you do work on a gas?

Answer 14

• internal energy of a gas

- increase in temperature