P1.2 Changes Of State

Question 1

What is density?

Answer 1

The amount of mass in a certain volume

It is a property of a material

Question 2

Why can objects with the same volume have different masses

Answer 2

Because they have different densities

Question 3

How do you calculate density (Kg/m3)

Answer 3

Density (kg/m3) = Mass (kg) ➗ volume (m3)

Question 4

Why is a substance denser as a solid than as a liquid or gas?

Answer 4

In 1cm3 of a substance in the solid there are more particles than in 1cm3 of the same substance as a gas.

The mass of 1cm3 of the solid is greater so the density is also greater

Question 5

What is temperature

Answer 5

It tells you how hot or cold something is

It is a measure of the average kinetic energy of the particles in a material

Question 6

How many °C is 0K

Answer 6

-273°C

Question 7

How many Kelvin is 0°C

Answer 7

273K

Question 8

What happens in terms of energy transfer when you heat water?

Answer 8

• when you heat water you transfer energy from the chemical store of a fuel to the thermal store of the water
• the water particles move faster or vibrate more

Question 9

What is the difference between energy in a thermal store and temperature?

Answer 9

• the energy in a thermal store is measured in Joules (J). It depends on the arrangement of the particles and how fast they are moving or vibrating

Temperature tells you about the average kinetic energy of the particles

Question 10

What happens when you heat things up ?

Answer 10

Heating can:
- change the energy stored within the system to increase the temperature

• produce a change of state
• make chemical reactions happen

Question 11

What is specific heat capacity?

Answer 11

The energy required to raise the temperature of 1Kg of a substance by 1K

Question 12

What does the amount of energy needed to raise the temperature of an object depend on?

Answer 12

• the type of material
• the mass of material
• the temperature rise

Question 13

What is the internal energy of a material?

Answer 13

The energy that relates to the motion, vibration, rotation and arrangement of the particles

Question 14

How do you calculate the change in thermal energy with specific heat capacity?

Answer 14

Change in thermal energy (J) = mass (kg) ✖️ specific heat capacity (J/Kg°C)) ✖️ change in temperature (°C)

Question 15

What does specific heat capacity tell you?

Answer 15

How resistant a material is to a change in temperature

Substances with a lower specific heat capacity heat up quicker

Substances with higher specific heat capacity are more resistant to temperature change

Question 16

Why is water a good material to use in a central heating system

Answer 16

It is more resistant to temperature change as it has a higher specific heat capacity

Question 17

Why are saucepans made of materials with low specific heat capacities?

Answer 17

Because they need to heat up quickly

Question 18

What is a change of state?

Answer 18

The process of moving from one physical state to another

Question 19

What is the process by which a liquid turns to a gas

Answer 19

Vaporising or boiling

Question 20

What is the process by which a gas turns to a liquid

Answer 20

Deposition

Question 21

What is the process by which a solid turns to a gas ?

Answer 21

Subliming

Question 22

How can you investigate cooling?

Answer 22

1. Melt salol in a test tube in a water bath. When the salol has melted place a thermometer in the test tube
2. Remove the test tube from the water bath and place it in a test tube rack
3. Take the temperature every minute and plot a graph of temperature against time
4. Use the graph to find the temp at which salol solidifies

Question 23

What happens when ice boils or melts

Answer 23

There is no temperature rise

The internal energy increases eventhough the temperature doesn’t

The energy that is transferred is breaking the attractive forces between the water molecules

Question 24

What is the specific latent heat of fusion?

Answer 24

The energy transferred when 1Kg of a substance changes from the solid to the liquid state or from the liquid to solid state

Question 25

What is the specific latent heat of vaporisation

Answer 25

The energy transferred when 1Kg of a substance changes from liquid to gas

Question 26

How do you calculate the thermal energy for a change in state with specific latent heat?

Answer 26

Thermal energy for a change in state (J) = mass ✖️ specific latent heat (J/Kg)

Question 27

What are similarities and differences between specific latent heat and specific heat capacity?

Answer 27

Similarity:
Both of them involve energy changes for 1Kg of a substance

Difference:
Latent heat is a change of state and heat capacity is about change of temperature