Unit 3 - Particle Model of Matter

Question 1

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

Answer 1

● Least dense: Gas
● Liquid
● Most dense: Solid

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 of a gas.

Answer 4

Separated, with no regular arrangement.
Particles can move freely.

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
change?

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

What is evaporation?

Answer 8

When a liquid changes into a gas state.

Question 9

What is is the opposite of evaporation?

Answer 9

Condensation, which is when a gas
changes into a liquid state.

Question 10

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

Answer 10

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 11

Explain the processes involved when a bathroom
mirror mists up.

Answer 11

● 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 12

What is the internal energy of a substance?

Answer 12

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

Question 13

How does heating affect the energy of a substance?

Answer 13

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

Question 14

What two things can heating a substance do?

Answer 14

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

Question 15

What three factors determine the temperature
change of a system?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Define specific heat capacity.

Answer 17

The amount of energy needed to
increase the temperature of 1kg of a
substance by 1°C.

Question 18

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

Answer 18

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

Question 19

Define specific latent heat.

Answer 19

The amount of energy needed to change
the state of 1kg of a substance with no
change in temperature.

Question 20

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

Answer 20

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

Question 21

What is the specific latent heat of fusion?

Answer 21

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

Question 22

What is the specific latent heat of vaporisation?

Answer 22

The energy required to change 1kg of a
substance from liquid state to gas state
(vapour) without a change in
temperature.

Question 23

Describe the motion of molecules in a gas.

Answer 23

They are in constant random motion.

Question 24

What factor affects the average kinetic energy of gas
molecules?

Answer 24

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

Question 25

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

Answer 25

Pressure of the gas will increase as the
temperature increases.

Question 26

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

Answer 26

● Kinetic energy of molecules increases
● Collisions between molecules becomes
more frequent
● Greater rate of change of momentum
● Greater force and therefore pressure

Question 27

If gas A is at a low pressure, and gas B is at a high
pressure, what can be said about the rate of
collisions in each gas?

Answer 27

● There are more collisions per second
in gas B than in gas A
● The rate of collisions is higher in B

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 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 and so time
between collisions increases
● 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