Edexcel IGCSE Physics C Change of State Questions

Practise change of state through particle models, heating and cooling graphs, specific heat capacity calculations and practical measurements.

Exam points

interpret temperature-time graphs to locate melting, freezing or boiling plateaus
explain particle arrangement, motion and kinetic store changes during heating and state change
calculate energy, mass or temperature change using specific heat capacity data

Covered syllabus points

5.8P Heating and energy stores 5.9P Melting, evaporation and boiling 5.10P Particle arrangement and motion 5.11P Change of state practical 5.12P Specific heat capacity 5.13P Thermal energy equation 5.14P Specific heat capacity practical

[Maximum number: 1]

Photograph 1 shows an outdoor swimming pool.

Photograph 1

The water in the swimming pool is heated by the Sun during the day.

State what happens to the average speed of the water molecules as the water is heated.

[Maximum number: 6]

This question is about liquid nitrogen.

(a)

The diagram shows the arrangement of particles in solid nitrogen.

Draw the arrangement of particles in liquid nitrogen.

solid

liquid

[ 2 ]

(b)

Describe the motion of the particles in liquid nitrogen.

[ 1 ]

(c)

Over time, the liquid nitrogen warms up and changes state from a liquid into a gas.

Describe the changes to the arrangement and motion of particles when the liquid nitrogen changes state.

[ 3 ]

[Maximum number: 2]

This question is about sound waves.

The speed of sound in liquids is greater than the speed of sound in gases.

Describe the arrangement of particles in liquids and in gases.

You may use diagrams to help your answer.

[Maximum number: 3]

This question is about liquid nitrogen.

Over time, the liquid nitrogen warms up and changes state from a liquid into a gas.

Describe the changes to the arrangement and motion of particles when the liquid nitrogen changes state.

[Maximum number: 4]

This question is about specific heat capacity.

After finishing the experiment, the student removes the aluminium block and places the container of water into a freezer.

The water loses energy at a constant rate and cools from $38^{\circ} \mathrm{C}$ to $-20^{\circ} \mathrm{C}$ .
The water freezes and turns into ice at $0^{\circ} \mathrm{C}$ .
Ice has a lower specific heat capacity than water.
Use the axes to sketch a temperature-time graph from when the water is placed in the freezer until it reaches its lowest temperature.

No calculations are required.

Figure for Question 5 — Edexcel IGCSE Physics

Marking points:
- line has two downward sloping sections of different gradient
- horizontal line at $0^\circ\mathrm{C}$ between the downward sloping sections
- line starts at $38^\circ\mathrm{C}$ and finishes at $-20^\circ\mathrm{C}$
- initial downward sloping line has smaller gradient than final downward sloping line

Ignore:
- where lines intersect the time axis
- start or finish time

Marking guidance:
- Sections do not need to be straight, but one must be clearly steeper than the other.
- Reject the horizontal-line marking point if there is more than one horizontal line lower than $38^\circ\mathrm{C}$ and higher than $-20^\circ\mathrm{C}$ .
- Judged by eye.
- Responses with initial and final downward sections parallel by eye can only score the horizontal-line and start/finish marking points.

[Maximum number: 2]

This question is about specific heat capacity.

State what is meant by the term specific heat capacity.

Answer:
- energy to change temperature by $1^\circ\mathrm{C}$
- per kilogram of mass

Accept:
- $1\ \mathrm{K}$

Marking guidance:
- DOP

[Maximum number: 4]

Energy is transferred from the Sun to the Earth.

Solar panels use energy from the Sun to heat water.

Figure for Question 7 — Edexcel IGCSE Physics

A mass of 1100 kg of cold water is in the solar panels at an initial temperature of 20 degrees C.

Calculate the final temperature of this water after it has been heated by the Sun for 2 hours.

[specific heat capacity of water = 4200 J/kg degrees C]

final temperature = ............ degrees C

[Maximum number: 2]

This question is about specific heat capacity.

A student uses this method to measure the specific heat capacity of water.
- place an aluminium block of known mass in an oven at a temperature of $220^{\circ} \mathrm{C}$
- place water of known mass in a container at a temperature of $20^{\circ} \mathrm{C}$
- leave the aluminium block in the oven for 10 minutes
- remove the aluminium block from the oven and place the block in the water
- measure the maximum temperature of the water after it has been heated by the aluminium block

The student uses their data to calculate the specific heat capacity of water.
Give two ways that they could improve their method to increase the accuracy of their value of specific heat capacity.

1

2

Any two from:
- MP1: leave the block in the oven for longer, or check it is definitely at $220^\circ\mathrm{C}$
- MP2: transfer the block from oven to water as quickly as possible
- MP3: add insulation to the container of water
- MP4: place a lid on the container of water
- MP5: use a container with low specific heat capacity or low thermal conductivity
- MP6: repeat and average, or remove anomalies

Examples:
- wrap it in wool
- use a polystyrene cup

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question (a)

Question (b)

Question (c)

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8