Particle Model Of Matter

Question 1

What is the definition of density?

Answer 1

The mass per unit volume of a material
p = m/v
Density (kg/m^3), Mass (kg), volume (m^3)

Question 2

State the different states of matter in order (least to most) of density of atoms

Answer 2

Least dense : gas
Liquid
Most dense : solid

Question 3

Describe the particle arrangement of a solid

Answer 3

Tightly packed in a regular arrangement
Particles can only vibrate on the spot

Question 4

Describe the particle arrangement of a liquid

Answer 4

Close together, but with an irregular arrangement
They can flow over each other

Question 5

Describe the particle arrangement of a gas

Answer 5

eparated, with no regular arrangement
Particles can move freely

Question 6

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

Answer 6

Mass

Question 7

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

Answer 7

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

Question 8

What is sublimation?

Answer 8

the process in which a solid changes directly into a gas

Question 9

What is evaporation?

Answer 9

When a liquid turns into a gas

Question 10

what is condesation?

Answer 10

the process by which a gas changes to a liquid

Question 11

When water boils in an open pan, why does the mass of the pan of water appear to decrease?

Answer 11

Some of the water will evaporate and turn into water vapour. This will leave the pan meaning the mass of the pan will decrease. The mass of the whole system however remains constant.

Question 12

Explain the processes involved when a bathroom mirror mists up?

Answer 12

● Hot water evaporates to form water vapour
● This water vapour lands on the cooler mirror
● The vapour condenses and returns to liquid
state on the mirror’s surface

Question 13

What is the internal energy of a substance?

Answer 13

● The energy stored by the particles
● The sum of the total kinetic and potential energies that make up the system

Question 14

How does heating affect the energy of a substance?

Answer 14

● Heating transfers energy to the substance
● It increases the energy of the particles that make up the substance

Question 15

What two things can heating a substance do?

Answer 15

1. Raise its temperature
2. Change the state of the substance

Question 16

What three factors determine the temperature change of a system?

Answer 16

1. Mass of substance being heated
2. Type of material (Specific heat capacity)
3. Energy inputted into the system

Question 17

State the equation used to calculate the temperature change when a substance is heated. Give the appropriate units

Answer 17

● ΔE = m c Δ𝛉
● Energy (J), Mass (kg), Specific Heat Capacity (J/kg/°C), Temperature (°C)

Question 18

Define specific heat capacity

Answer 18

it is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 degrees celsius

Question 19

Describe how the internal energy and temperature of a substance changes when a change of state occurs.

Answer 19

● The internal energy of the substance will be increased or decreased
● The temperature of the substance will remain constant

Question 20

Define specific latent heat

Answer 20

The amount of energy needed to change 1kg of a substance from one state to another without changing its temperature

Question 21

State the equation for the energy required to change state. Give appropriate units

Answer 21

● Energy to change state = mass x specific latent heat
● Energy (J), Mass (kg), Specific latent heat (J/kg)

Question 22

What is the specific latent heat of fusion?

Answer 22

The energy required to change 1kg of a substance from solid state to liquid state without a change in temperature.

Question 23

What is the specific latent heat of vaporisation?

Answer 23

The energy required for 1 kg of a liquid to change state to a gas without a change in temperature

Question 24

Describe the motion of molecules in a gas

Answer 24

They are in constant random motion

Question 25

What factor affects the average kinetic energy of gas molecules?

Answer 25

• The temperature of the substance
• The higher the temperature, the higher the average kinetic energy of the molecules

Question 26

What effect does increasing temperature have on the pressure of a gas when held at constant volume?

Answer 26

Pressure of the gas will increase as the temperature increases.

Question 27

Why does pressure increase as temperature increase (at a constant volume)?

Answer 27

• Kinetic energy of the molecules increase
• Collisions between molecules become more frequent
• Greater rate of change of momentum
• Greater force and therefore pressure

Question 28

Describe the force that the pressure of a gas exerts on the walls of its container.

Answer 28

• The net force acts at right-angles to the container’s surface
• The magnitude of the force increases as pressure increases

Question 29

Explain how increasing the volume of a gas results in a decrease of pressure.

Answer 29

● Molecules become more spread out so collisions become less frequent
● This reduces the rate of collisions
● Rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure

Question 30

What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?

Answer 30

It is constant.
p V = constant

Question 31

What is the unit used for pressure?

Answer 31

Pascal (Pa)

Question 32

What increases when you do work on a gas?

Answer 32

● The internal energy of the gas
● This can also lead to an increase of temperature

Question 33

Why does the temperature of air inside a bike pump increase when it is pumped?

Answer 33

● Work is done on a gas when it is compressed
● Doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules
● Temperature increases with an increase of average kinetic energy