P1.2 - Changes Of State

Question 1

What is density?

Answer 1

Density is a measure of how much matter is contained within a given volume

Question 2

What is the formula for density?

Answer 2

Density (kgm-3) = Mass (kg) / Volume (m3)

Question 3

Why do different states of matter have very different densities?

Answer 3

• Owing to the fact the particles will be arranged
  differently in the different states.
• Particles are closer together in the solid state
  than in the gas state -> More particles in a given
  volume - More mass in a given volume ->
  Higher density

Question 4

What does density depend on?

Answer 4

The particle arrangement and the mass of the particles.

Question 5

What does temperature tell you?

Answer 5

• How hot or cold something is.
• If an object feels cold, it has a low temperature.
• If an object feels hot, it has a high temperature.

Question 6

Define temperature.

Answer 6

Temperature is a measure of the average kinetic energy of particles in a substance.

Question 7

What is heat energy/energy in the thermal store and what does it depend on?

Answer 7

• Measured in J and kJ.
• Heat energy of a substance manifests as kinetic
  energy of its particles.
• The heat energy of a substance is a measure of
  the total internal energy in a substance.
• Depends on the arrangement of the particles and
  how fast they are moving or vibrating.

Question 8

What happens as you heat something up? (3 points)

Answer 8

• Increases the energy stored within the system to
  increase the temperature.
• Produces a change of state.
• Makes chemical reactions happen.

Question 9

What is internal energy of a substance the sum of?

Answer 9

The kinetic energy and potential energy of its particles.

Question 10

What are the units of temperature?

Answer 10

• Degrees Celsius (‘C)

- Kelvin (K)

Question 11

How many kelvin in 0 degree Celsius?

Answer 11

• 273K

- K = C + 273

Question 12

What 3 factors determine how much energy is required to increase the temperature of a substance?

Answer 12

• The type of material/Nature of the material itself.
• The overall temperature change being brought
  about.
• The mass of the substance being heated.

Question 13

What does heating do to a material?

Answer 13

Increases the internal energy which relates to the motion, vibration, rotation, and arrangement of the particles.

Question 14

What is the specific heat capacity of a substance?

Answer 14

The heat energy required to raise the temperature of 1kg of a substance by 1 Kelvin (J/kgK).

Question 15

What does the specific heat capacity of a substance tell you?

Answer 15

• How easy or difficult it is to change the
  temperature of a substance.
• How resistant a material is to a change in
  temperature.

Question 16

What does a lower specific heat capacity mean?

Answer 16

The lower the specific heat capacity, the quicker/easier the substance will change temperature, as less energy is required.

Question 17

What equation do you need to apply in relation to specific heat capacity?

Answer 17

• E=mcθ
• Change in thermal energy (J) = Mass (kg) x
  Specific heat capacity (J/kgK) x Change in
  temperature (K)

Question 18

Why aren’t gold, platinum and some other metals used to make saucepans even though they have small specific heat capacities which is useful as they heat up quickly?

Answer 18

They are very expensive and some metals are poisonous.

Question 19

What does a temperature-time graph show?

Answer 19

• How the temperature of a substance changes
  over time.
• The melting and boiling point of a substance
  which corresponds to the horizontal lines.

Question 20

What do the straight lines in a temperature-time of water show? Explain.

Answer 20

• Melting point and boiling point.
• There is no temperature change during a state
  change.
• No kinetic energy change during a state
  change
• Internal energy is increasing and that energy is
  transferred to break the attractive forces between
  the water molecules.

Question 21

What are the two types of energy that particles contain and what are they due to?

Answer 21

• Kinetic energy - Energy due to the motion of the
  particles.
• Potential Energy - Energy due to the position of
  the particles.

Question 22

When do you use specific heat capacity and specific latent heat and why?

Answer 22

• Specific heat capacity - Temperature change
  during heating/cooling - Only kinetic energy has
  changed.
• Specific latent heat - State change during
  heating/cooling - Only potential energy has
  changed.

Question 23

What is the specific latent heat of fusion (or melting) (Lf)?

Answer 23

The heat energy transferred when 1kg of a substance changes from the solid state to the liquid state (or vice versa).

Question 24

What is the specific latent heat of vaporisation (Lv)?

Answer 24

The heat energy transferred when 1kg of a substance changes from the liquid state to the gas state (or vice versa).

Question 25

What equation do you need to apply in relation to specific latent heat?

Answer 25

• E=mL
• Thermal energy transferred for a change in state
  (J) = mass (kg) x specific latent heat (J/kg)