3. Particle Model

Question 1

What are the three states of matter?

Answer 1

Solid, liquid and gas.

Question 2

Why are solids and liquids difficult to compress?

Answer 2

Their particles are close together with almost no gaps.

Question 3

What is the particle arrangement in a solid?

Answer 3

Particles are tightly packed in fixed positions; solids have fixed shape and volume.

Question 4

What is the particle arrangement in a liquid?

Answer 4

Particles are close together but can move past each other; liquids have fixed volume but take the shape of their container.

Question 5

What is the particle arrangement in a gas?

Answer 5

Particles are far apart and move randomly; gases are compressible and expand to fill their container.

Question 6

What is density?

Answer 6

The mass per unit volume of a substance.

Question 7

What is the equation for density?

Answer 7

ρ = m / V

Question 8

Units for ρ = m / V

Answer 8

ρ in kilograms per cubic metre (kg/m³), m in kilograms (kg), V in cubic metres (m³)

Question 9

Why do different materials have different densities?

Answer 9

Because of differences in the mass of their particles and the spacing between them.

Question 10

What happens to temperature as energy is added to a system?

Answer 10

The temperature increases unless a change of state occurs.

Question 11

What happens to internal energy as a system is heated?

Answer 11

It increases — particles move faster and/or further apart.

Question 12

What happens to internal energy during a change of state?

Answer 12

Energy is used to break or form intermolecular bonds rather than raise temperature.

Question 13

At melting or boiling point

Answer 13

what happens as energy continues to be added?

Question 14

Is a change of state reversible?

Answer 14

Yes, if no material is lost.

Question 15

What are the names of the changes of state?

Answer 15

Melting, freezing, boiling, condensation, and sublimation.

Question 16

What is sublimation?

Answer 16

Change of state directly from solid to gas (or vice versa) without becoming a liquid.

Question 17

What is specific latent heat?

Answer 17

The energy required to change the state of 1 kg of a substance at constant temperature.

Question 18

What is the equation for specific latent heat?

Answer 18

E = m L

Question 19

Units for E = m L

Answer 19

E in joules (J), m in kilograms (kg), L in joules per kilogram (J/kg)

Question 20

What is latent heat of fusion?

Answer 20

Energy needed to change between solid and liquid.

Question 21

What is latent heat of vaporisation?

Answer 21

Energy needed to change between liquid and gas.

Question 22

What is specific heat capacity?

Answer 22

Energy needed to raise 1 kg of a substance by 1 °C.

Question 23

What is the equation for specific heat capacity?

Answer 23

ΔE = m c Δθ

Question 24

Units for ΔE = m c Δθ

Answer 24

ΔE in joules (J), m in kilograms (kg), c in joules per kilogram per degree Celsius (J/kg°C), Δθ in °C

Question 25

What is internal energy?

Answer 25

The total kinetic and potential energy of particles in a system.

Question 26

What happens when gas particles collide with the walls of a container?

Answer 26

They exert a force on the walls, creating pressure.

Question 27

What factors increase gas pressure?

Answer 27

Higher temperature, smaller volume, or more particles in the same volume.

Question 28

What is the relationship between gas pressure and volume (at constant temperature)?

Answer 28

p × V = constant (Boyle’s law).

Question 29

Units for p × V = constant

Answer 29

p in pascals (Pa), V in cubic metres (m³)

Question 30

Why does gas pressure increase when temperature rises (at constant volume)?

Answer 30

Particles move faster and collide with walls more often and with greater force.

Question 31

What does absolute zero represent?

Answer 31

The temperature (0 K) at which particles have minimum possible energy.

Question 32

How does temperature in kelvin relate to particle energy?

Answer 32

Temperature in K is directly proportional to the average kinetic energy of particles.

Question 33

What happens to a gas if it is compressed quickly without heat loss?

Answer 33

Its temperature increases because work is done on it.

Question 34

What happens to a gas that expands quickly?

Answer 34

It cools because it does work on the surroundings.

Question 35

What does doing work on a gas do?

Answer 35

Transfers energy to the gas, increasing its internal energy and possibly its temperature.

Question 36

Why do aerosol cans become cold when used?

Answer 36

Gas inside expands rapidly, doing work on the surroundings, reducing internal energy and temperature.

Question 37

How can the density of an irregular solid be found experimentally?

Answer 37

Measure its mass and volume by water displacement, then use ρ = m/V.

Question 38

How can the density of a liquid be measured?

Answer 38

Find the mass of a known volume using a balance and measuring cylinder.