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GCSE Physics · GCSEChapter 3 · Specific heat capacity
GCSE · Chapter 3

Specific heat capacity

By the end of this chapter you will be able to

  • Calculate the energy needed to warm a mass of a material by a given temperature rise
  • Rearrange E = mc(change in temperature) to find any one of the quantities
  • Explain what specific heat capacity means, and why water is used in heating systems
  • Describe how to measure the specific heat capacity of a metal, and explain how heat loss affects the result

You should already know

  • Energy stores and transfers (Chapter 1)
  • Efficiency and power calculations (Chapter 2)

Where this leads

  • Particle model and internal energy (Chapter 9)
  • Energy resources and the energy supply (Chapter 4)

GCSE Physics. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Use E = m c change in theta to calculate the energy needed to change the temperature of a material, Explain specific heat capacity as the energy needed per kilogram per degree Celsius, Rearrange the equation to find the mass, the temperature change or the specific heat capacity, Describe the practical to determine the specific heat capacity of a metal block using an electric heater, a thermometer and insulation, Evaluate the effect of energy lost to the surroundings on a measured value.

Exercise P  Do you remember?

1
FWhat is 2 x 4.5? Write the number.
2
FWhat is 30 x 300? Write the number.
3
FWhat is the power of a heater that transfers 2000 J in 100 s? Write the number of watts.
4
FWhat is 0.5 kg in grams? Write the number.
5
FWhich is a better material for keeping a room warm: a material that conducts heat well or one that is an insulator? Write insulator or conductor.
3.1

What is specific heat capacity?

GCSE
Explain specific heat capacity as the energy needed per kilogram per degree Celsius
Video lesson: What is specific heat capacity?Coming soon
Context. Ellie fills two pans with the same mass of water and the same mass of iron. She puts both on the same hob. “The iron gets hot very quickly,” she says, “but the water takes much longer.” Different materials need different amounts of energy to warm up.

The specific heat capacity, written c, of a material is the energy needed to raise the temperature of 1 kg of it by 1 °C. Its unit is joules per kilogram per degree Celsius, J/kg °C. A material with a high specific heat capacity needs a lot of energy to warm up, and it also gives out a lot of energy when it cools down.

SubstanceSpecific heat capacity (J/kg degC)
water4200
aluminium900
iron450
copper385
Specific heat capacities of some common materials (J/kg °C)

Key ideas

  • Specific heat capacity c = energy needed to warm 1 kg by 1 °C.
  • Its unit is J/kg °C.
  • Water has a high specific heat capacity: 4200 J/kg °C.
  • Metals have lower values, so they warm up quickly.
Worked example 3.1.1
Using the table, how much energy is needed to warm 1 kg of iron by 1 °C? Write the number of joules.

Method. Read the value from the table.

  1. Read. The specific heat capacity of iron is 450 J/kg °C.
    c = 450
  2. Interpret. So 450 J of energy warms 1 kg of iron by 1 °C.
    450 J for 1 kg, 1 °C
  3. Write the answer.
    450 J

Check. Iron needs less energy than water for the same mass and rise. ✓

Worked example 3.1.2
Which needs more energy to warm by 1 °C: 1 kg of water or 1 kg of copper? Write water or copper.

Method. Compare the two values.

  1. Water. Water has c = 4200 J/kg °C.
    4200
  2. Copper. Copper has c = 385 J/kg °C.
    385
  3. Compare. 4200 is much bigger than 385, so water needs more energy.
    4200 > 385
  4. Write the answer.
    water

Check. Water warms up slowly and cools slowly too. ✓

Worked example 3.1.3
Why is water used to store heat in a central heating system? Write one reason in one sentence.

Method. Think about the specific heat capacity of water.

  1. Think. Water has a high specific heat capacity.
    high c
  2. Link. So a given mass of water can store a lot of energy for each degree it is warmed.
    stores energy
  3. Write the answer.
    Accept any sentence that says water has a high specific heat capacity, so it can store a lot of energy.

Check. Water is a useful store because it holds a lot of energy. ✓

Watch out

Watch out: specific heat capacity is for 1 kg and 1 °C. Do not confuse it with the energy you transfer in total; that depends on the mass and the rise.

Exam tip

Exam tip. A high specific heat capacity means “hard to heat up and hard to cool down”. Use that idea in explanations.

Exercise 3A  Meaning of specific heat capacity

1
FWhat is the unit of specific heat capacity? Write the unit.
2
FWrite the specific heat capacity of water. Write the number.
3
FWhich metal in the table has the lowest specific heat capacity? Write the name.
4
FWhich material in the table needs the most energy to warm up by 1 °C per kilogram? Write the name.
5
FHow much energy is needed to warm 1 kg of aluminium by 1 °C? Write the number of joules.
6
FWhich three materials in the table need less energy than water to warm 1 kg by 1 °C? Write three names.
7
RA pupil says “a material with a high specific heat capacity warms up quickly.” Explain why this is wrong. Accept any sentence that says a high value means it takes a lot of energy to warm up, so it heats more slowly.
8
PSAhmed says water and iron of the same mass are heated with the same energy. The water warms by less. Is Ahmed right? Write yes or no.
9
RExplain why a saucepan is made of metal but its handle is often made of plastic, using specific heat capacity and conduction. Accept any answer that says metal warms up fast and conducts energy well, while a plastic handle stays cool to touch.
10
RExplain why the water in a lake takes a long time to warm up in spring. Accept any answer that says water has a high specific heat capacity, so it needs a lot of energy to warm up.
11
PSA material has a specific heat capacity of 900 J/kg °C. How much energy is needed to warm 3 kg of it by 1 °C? Write the number of joules.
12
PSTwo blocks of the same mass are heated by the same energy. Block X has c = 450 J/kg °C and block Y has c = 900 J/kg °C. Which block has the bigger temperature rise? Write X or Y.
13
RExplain why a cooking oil is hot after 30 minutes in a pan, but the water in the same pan is still warm. Accept any answer that uses specific heat capacity: the oil has a lower value, so it warms by more for the same energy.
3.2

Calculating the energy to warm a material

GCSE
Use E = m c change in theta to calculate the energy needed to change the temperature of a material
Video lesson: Calculating the energy to warm a materialComing soon
Context. Mr Patel is heating water for a bath. He needs to know how much energy the water will take in, to check the cost. He uses the equation E = m c Δθ, where Δθ (the Greek letter theta) is the temperature change.

The energy needed to change the temperature of a material is:

E = m x c x Δθ

where E is the energy in joules, m is the mass in kilograms, c is the specific heat capacity in J/kg °C, and Δθ is the temperature change in °C. The more mass you have, and the bigger the rise, the more energy you need.

SubstanceSpecific heat capacity (J/kg degC)
water4200
aluminium900
iron450
copper385
Use these values for c in the questions

Key ideas

  • E = m x c x Δθ, in joules, with m in kilograms and Δθ in °C.
  • A rise of 10 °C and a fall of 10 °C use the same numbers: use the size of the change.
  • Convert grams to kilograms first: 500 g = 0.5 kg.
  • Always write the unit J at the end of your answer.
Worked example 3.2.1
Calculate the energy needed to warm 2 kg of water by 10 °C. Write the number of joules.

Method. Use E = m x c x Δθ with c = 4200 J/kg °C.

  1. Take the numbers. m = 2 kg, c = 4200 J/kg °C, Δθ = 10 °C.
    m = 2, c = 4200, Δθ = 10
  2. Multiply. E = 2 x 4200 x 10 = 84000 J.
    2 x 4200 x 10 = 84000
  3. Write the answer.
    84000 J

Check. 84000 / (4200 x 10) = 2 kg. ✓

Worked example 3.2.2
Calculate the energy needed to warm 0.5 kg of aluminium from 20 °C to 40 °C. Write the number of joules.

Method. Find the temperature change first: 40 - 20 = 20 °C.

  1. Temperature change. Δθ = 40 - 20 = 20 °C.
    20
  2. Multiply. E = 0.5 x 900 x 20 = 9000 J.
    0.5 x 900 x 20 = 9000
  3. Write the answer.
    9000 J

Check. 9000 / (900 x 20) = 0.5 kg. ✓

Worked example 3.2.3
Calculate the energy needed to warm 2 kg of copper by 5 °C. Write the number of joules.

Method. Use E = m x c x Δθ.

  1. Take the numbers. m = 2 kg, c = 385 J/kg °C, Δθ = 5 °C.
    m = 2, c = 385, Δθ = 5
  2. Multiply. E = 2 x 385 x 5 = 3850 J.
    2 x 385 x 5 = 3850
  3. Write the answer.
    3850 J

Check. 3850 / (2 x 5) = 385 J/kg °C. ✓

Watch out

Watch out: convert grams to kilograms before you use E = mcΔθ. 250 g is 0.25 kg, not 250 kg.

Exam tip

Exam tip. Write the equation, then the numbers with their units, then calculate. Give your answer in joules.

Exercise 3B  Energy to change the temperature

1
FCalculate the energy needed to warm 1 kg of water by 10 °C. Write the number of joules.
2
FCalculate the energy needed to warm 2 kg of iron by 10 °C. Write the number of joules.
3
FCalculate the energy needed to warm 3 kg of water by 5 °C. Write the number of joules.
4
FCalculate the energy needed to warm 0.5 kg of water by 20 °C. Write the number of joules.
5
FCalculate the energy needed to warm 500 g of copper by 10 °C. Write the number of joules.
6
FCalculate the energy needed to warm 4 kg of aluminium from 15 °C to 25 °C. Write the number of joules.
7
PSCalculate the energy needed to warm 2 kg of water from 12 °C to 52 °C. Write the number of joules.
8
PSA kettle holds 1.5 kg of water at 18 °C. The water is heated to 100 °C. Calculate the energy needed. Write the number of joules.
9
PSCalculate the energy needed to warm 200 g of water by 25 °C. Write the number of joules.
10
PSTwo pans have 1 kg of water each. One is warmed by 10 °C and one by 20 °C. How much more energy does the second pan need? Write the number of joules.
11
PSA 2 kg block of a metal is warmed by 5 °C and takes 4500 J of energy. Calculate the specific heat capacity of the metal. Write the number in J/kg °C.
12
RExplain why the answer to a calculation of E = m c Δθ is in joules, using the units of each quantity. Accept any answer that multiplies kg by J/kg °C by °C and gives J.
13
RA pupil heats 1 kg of water by 10 °C in 1 minute with a heater of 4200 W. The pupil says the energy transferred is 4200 J. Is the pupil right? Write yes or no.
3.3

Rearranging the equation

GCSE
Rearrange the equation to find the mass, the temperature change or the specific heat capacity
Video lesson: Rearranging the equationComing soon
Context. A school technician uses an electric heater to warm a block of metal. She knows the energy and the mass, and she wants to find the specific heat capacity. She has to rearrange the equation first.

E = m c Δθ can be rearranged to find any one of the four quantities:

m = E / (c x Δθ), c = E / (m x Δθ), Δθ = E / (m x c)

Cover the quantity you want with your finger, and the rest of the equation shows you what to do.

Key ideas

  • To find Δθ: divide E by (m x c).
  • To find m: divide E by (c x Δθ).
  • To find c: divide E by (m x Δθ).
  • Check your answer by putting it back into E = m c Δθ.
Worked example 3.3.1
Energy 84000 J is needed to warm 2 kg of water. Find the temperature rise. Write the number in °C.

Method. Rearrange to Δθ = E / (m x c).

  1. Rearrange. Δθ = 84000 / (2 x 4200).
    84000 / 8400
  2. Divide. Δθ = 84000 / 8400 = 10 °C.
    84000 / 8400 = 10
  3. Write the answer.
    10 °C

Check. 2 x 4200 x 10 = 84000 J. ✓

Worked example 3.3.2
An aluminium block gains 9000 J and warms by 10 °C. Find its mass. Write the number in kilograms.

Method. Rearrange to m = E / (c x Δθ).

  1. Rearrange. m = 9000 / (900 x 10).
    9000 / 9000
  2. Divide. m = 9000 / 9000 = 1 kg.
    9000 / 9000 = 1
  3. Write the answer.
    1 kg

Check. 1 x 900 x 10 = 9000 J. ✓

Worked example 3.3.3
A 0.5 kg block gets 9000 J of energy and warms by 40 °C. Find its specific heat capacity. Write the number in J/kg °C.

Method. Rearrange to c = E / (m x Δθ).

  1. Rearrange. c = 9000 / (0.5 x 40) = 9000 / 20.
    9000 / 20
  2. Divide. c = 9000 / 20 = 450 J/kg °C.
    9000 / 20 = 450
  3. Write the answer.
    450 J/kg °C

Check. 0.5 x 450 x 40 = 9000 J. ✓

Watch out

Watch out: multiply m and Δθ before you divide when you rearrange for c. The bracket matters: E / m / Δθ is not the same as E / (m x Δθ) unless you do the steps in order.

Exam tip

Exam tip. Write the rearranged equation first, then substitute. Keep the units on every line.

Exercise 3C  Rearranging to find the rise, the mass and the specific heat capacity

1
FEnergy 42000 J warms 1 kg of water. Find the temperature rise. Write the number in °C.
2
FEnergy 63000 J is needed to warm water with a mass of 3 kg. Find the temperature rise. Write the number in °C.
3
FEnergy 3850 J is needed to warm 2 kg of copper. Find the temperature rise. Write the number in °C.
4
FEnergy 18000 J warms a 0.5 kg block of aluminium (c = 900 J/kg °C). Find the temperature rise. Write the number in °C.
5
FEnergy 84000 J warms an unknown mass of water (c = 4200 J/kg °C) by 10 °C. Find the mass. Write the number in kilograms.
6
FEnergy 9000 J warms an unknown mass of iron (c = 450 J/kg °C) by 20 °C. Find the mass. Write the number in kilograms.
7
FA 2 kg block gets 4500 J and warms by 5 °C. Find its specific heat capacity. Write the number in J/kg °C.
8
PSA 1.5 kg block of metal gets 13500 J and warms by 10 °C. Find its specific heat capacity. Write the number in J/kg °C.
9
PSA heater transfers 30240 J to 0.6 kg of water (c = 4200 J/kg °C), and all the energy goes into the water. Find the temperature rise. Write the number in °C.
10
PSA pupil heats 1 kg of a metal and records 4500 J and a rise of 5 °C. Find the specific heat capacity and say which metal from the table it is most likely to be. Write the metal name.
11
RExplain why the temperature rise is smaller for a block of a material with a larger specific heat capacity, if the energy supplied is the same. Accept any answer that says E = m c Δθ means a bigger c gives a smaller Δθ.
12
PSFind the mass of 900 J/kg °C aluminium that gains 27000 J when it warms by 30 °C. Write the number in kilograms.
13
RA block of mass 0.25 kg is given 2250 J and warms by 20 °C. Find its specific heat capacity. Write the number in J/kg °C.
3.4

Practical: specific heat capacity of a metal block

GCSE
Describe the practical to determine the specific heat capacity of a metal block using an electric heater, a thermometer and insulation
Video lesson: Practical: specific heat capacity of a metal blockComing soon
Context. The class wants to find out which metal is in a block that the teacher has labelled only with its mass. They will heat it with a low-voltage heater and measure the rise in temperature. The teacher runs the heater; the pupils read the thermometer and record the results.

In the practical, a metal block of known mass has a hole with a heater inside it. The block is wrapped in insulation to reduce heat loss. A thermometer is placed in a second hole. The heater is switched on for a known time, and the energy from the heater is found from its voltage and current: E = V x I x t. The temperature is recorded before and after heating. The specific heat capacity is then c = E / (m x Δθ).

Safety: the heater is low-voltage, but the practical is done only with a teacher or a grown-up. Do not touch the block while it is hot.

insulation (lagging) around the blockmetal blockheaterthermometerlow-voltage supply12 V, 2.5 Ause with a teacher
The metal block, heater, thermometer and insulation (low-voltage supply, teacher supervised)
QuantityValue
start temperature20 degC
end temperature60 degC
temperature rise40 degC
energy from heater (V x I x t)9000.0 J
mass of block0.5 kg
specific heat capacity (E / m x rise)450 J/kg degC
Example results (from the worked numbers in this section)

Key ideas

  • Energy from the heater: E = V x I x t, in joules.
  • Specific heat capacity: c = E / (m x Δθ).
  • Use the mass of the block in kilograms.
  • Insulation and a lid reduce the heat lost, so the result is more accurate.
Worked example 3.4.1
A 12 V heater carries a current of 2.5 A for 300 s in a 0.5 kg block. The block warms by 40 °C. Find the energy from the heater. Write the number of joules.

Method. Use E = V x I x t.

  1. Power. Power = V x I = 12 x 2.5 = 30 W.
    30 W
  2. Energy. E = P x t = 30 x 300 = 9000 J.
    9000 J
  3. Write the answer.
    9000 J

Check. 9000 J / 300 s = 30 W. ✓

Worked example 3.4.2
Using the same block, E = 9000 J, m = 0.5 kg and Δθ = 40 °C. Calculate the specific heat capacity. Write the number in J/kg °C.

Method. Use c = E / (m x Δθ).

  1. Multiply. m x Δθ = 0.5 x 40 = 20.
    20
  2. Divide. c = 9000 / 20 = 450 J/kg °C.
    9000 / 20 = 450
  3. Write the answer.
    450 J/kg °C

Check. The value matches iron in the table. ✓

Worked example 3.4.3
A pupil says the calculated c is 500 J/kg °C, but the true value is 450 J/kg °C. Suggest one reason why the result is too high, in one sentence.

Method. Think about where the energy goes.

  1. Think. If some of the heater’s energy escapes to the surroundings, the block gains less energy than the heater supplied.
    energy lost
  2. Link. The calculation uses the heater energy, so it overestimates the energy absorbed and gives a value that is too high.
    overestimate
  3. Write the answer.
    Accept any sentence that says heat is lost to the surroundings, so the calculated energy is too large.

Check. More insulation would reduce this error. ✓

Watch out

Watch out: the energy used in the calculation is the energy from the heater. Heat lost to the surroundings means the block gains less than this, so c is overestimated unless the loss is reduced.

Exam tip

Practical safety. Always use the low-voltage supply, keep wires away from water, and let the block cool before handling it.

Exercise 3D  The practical and the effect of heat loss

1
FIn the practical, what is the purpose of the insulation around the block? Write one word.
2
FWhat is the energy supplied by a 12 V heater carrying 2.5 A for 300 s? Write the number of joules.
3
FIn the practical, which piece of equipment measures the temperature of the block? Write the name.
4
FWhy is the mass of the block measured before the practical? Write the reason in one sentence. Accept any sentence that says the mass is needed in the calculation of c.
5
FA block warms from 20 °C to 60 °C. Find the temperature rise. Write the number in °C.
6
FA 0.4 kg block of iron is heated by 20 °C. Calculate the energy it gains. Write the number of joules.
7
PSA pupil uses a heater of 40 W for 150 s on a 0.5 kg block. Calculate the energy from the heater. Write the number of joules.
8
PSUsing the answer to the last question, the block warms by 24 °C. Calculate the specific heat capacity. Write the number in J/kg °C.
9
RA pupil does not use a lid or insulation, and the measured c is 600 J/kg °C. Explain why the value is too large. Accept any answer that says heat escapes to the surroundings, so the energy absorbed by the block is smaller than the energy supplied.
10
RSuggest two improvements to the practical to make the value of c more accurate. Accept any two of: use insulation, use a lid, use a thermometer with finer divisions, repeat and find the average, or wait until the temperature is steady.
11
RThe final temperature of a block is read 2 °C too low, but the starting temperature is correct. Is the calculated value of c too high or too low? Write high or low.
3.5

Why water is used in heating and cooling

GCSE
Explain specific heat capacity as the energy needed per kilogram per degree Celsius
Video lesson: Why water is used in heating and coolingComing soon
Context. A central heating system uses hot water to carry energy from the boiler to the radiators. Why is water chosen, and not iron or copper? The answer is the high specific heat capacity of water, which lets it store and carry a large amount of energy.

Because water has a high specific heat capacity, a given mass of water can store a lot of thermal energy for each degree of rise. It is cheap, safe and easy to pump round a system. Cooling systems in cars also use water for the same reason: it can take in a lot of energy with only a small rise in temperature.

Key ideas

  • Water: high c, so it stores a lot of energy for a given rise.
  • A high c means the temperature changes slowly when energy is added or removed.
  • Water is used in heating and cooling systems for this reason.
  • Coastal areas have milder temperatures because the sea warms and cools slowly.
Worked example 3.5.1
Two 1 kg masses are each heated by 10 °C. One is water and one is iron. Calculate the energy transferred to the water. Write the number of joules.

Method. Use E = m c Δθ with c = 4200 J/kg °C for water.

  1. Take the numbers. m = 1 kg, c = 4200 J/kg °C, Δθ = 10 °C.
    m = 1, c = 4200, Δθ = 10
  2. Multiply. E = 1 x 4200 x 10 = 42000 J.
    1 x 4200 x 10 = 42000
  3. Write the answer.
    42000 J

Check. For the iron, E = 1 x 450 x 10 = 4500 J. ✓

Worked example 3.5.2
Using the answer above, how many times more energy does the water need than the iron for the same mass and rise? Write the number.

Method. Divide the two energies.

  1. Iron. E for iron = 1 x 450 x 10 = 4500 J.
    4500 J
  2. Divide. Water / iron = 42000 / 4500.
    42000 / 4500
  3. Simplify. Divide both by 4500: 42000 / 4500 = 9.33 (to 3 significant figures), which is 9.33 times.
    9.33
  4. Write the answer.
    9.33

Check. 4200 / 450 = 9.33 to 3 significant figures. ✓

Worked example 3.5.3
Give one reason why water is a good coolant for a car engine, in one sentence. Accept any sentence that says water has a high specific heat capacity, so it absorbs a lot of energy with a small rise in temperature.

Method. Use the idea of specific heat capacity.

  1. Think. The water must take in a lot of thermal energy from the engine.
    takes in energy
  2. Link. Because c is high, the water stays cooler while it absorbs the energy.
    stays cooler
  3. Write the answer.
    Accept any sentence that says water has a high specific heat capacity, so it absorbs a lot of energy with a small rise in temperature.

Check. ✓

Watch out

Watch out: a high specific heat capacity does not mean “hot”. It means the material changes temperature slowly for a given energy.

Exam tip

Exam tip. In an explanation question, link the property to the effect: “high c, so it stores more energy for the same rise”.

Exercise 3E  Water, heating and cooling

1
FWhy is water used in central heating systems? Write one word: high or low.
2
FCalculate the energy needed to warm 1 kg of water by 25 °C. Write the number of joules.
3
FA 10 kg block of copper is heated by 10 °C. Calculate the energy transferred. Write the number of joules.
4
PSWhich would warm up more for the same energy: 1 kg of water or 1 kg of copper? Write water or copper.
5
PSA kettle transfers 84000 J to 2 kg of water. The water has c = 4200 J/kg °C. Find the temperature rise. Write the number in °C.
6
RExplain in one sentence why a hot-water bottle stays warm for a long time. Accept any sentence that says water has a high specific heat capacity, so it cools slowly.
7
PSTwo equal masses of water start at the same temperature. Mass 1 is given 1000 J more energy than mass 2. Which ends with the higher temperature? Write 1 or 2.
8
RA builder says “this metal block will take longer to heat up than the water in the bucket, if they have the same mass.” Is the builder right? Write yes or no.
9
PSA 2 kg block of iron cools from 80 °C to 60 °C. Calculate the energy it gives out. Write the number of joules.
10
RExplain why the sea is warmer in summer for longer than the land, using specific heat capacity. Accept any answer that says water has a high specific heat capacity so it takes longer to warm up and cool down.

Chapter summary

SkillMethod
Define specific heat capacityEnergy needed to warm 1 kg by 1 °C; unit J/kg °C
Calculate energyE = m x c x Δθ, with m in kg
RearrangeDivide E by the other two quantities multiplied together
Find c in the practicalE = V x I x t, then c = E / (m x Δθ)
Evaluate heat lossHeat lost to the surroundings makes c too high unless insulation is used

Can you…?

  • I can define specific heat capacity and give its unit
  • I can calculate the energy needed to warm a material
  • I can rearrange E = mcΔθ to find the mass, rise or c
  • I can describe the practical and the energy from a heater
  • I can explain how heat loss affects the value of c

Key terms

specific heat capacity (c)
the energy needed to raise the temperature of 1 kg of a material by 1 °C
temperature change (Δθ)
the final temperature minus the starting temperature, in °C
insulation
a material that slows the transfer of thermal energy
low-voltage supply
a power supply that gives a safe, low voltage, used with a teacher

Exercise 3Z  Check-up

1
What is the unit of specific heat capacity? Write the unit.
2
Calculate the energy needed to warm 4 kg of water by 5 °C. Write the number of joules.
3
Calculate the energy needed to warm 0.5 kg of iron by 20 °C. Write the number of joules.
4
Calculate the temperature rise when 42000 J warms 1 kg of water. Write the number in °C.
5
Calculate the mass of aluminium that gains 18000 J when it warms by 20 °C. Write the number in kilograms.
6
A block of 2 kg gets 9000 J and warms by 5 °C. Find its specific heat capacity. Write the number in J/kg °C.
7
A 12 V heater carries 2 A for 100 s. Calculate the energy supplied. Write the number of joules.
8
Why does a heater with no insulation give a value of c that is too high? Write one short reason.
9
A pupil says water is used in heating systems because it has a low specific heat capacity. Is the pupil right? Write yes or no.
10
A 3 kg block of copper gains 3850 J. Find its temperature rise. Write the number in °C to 2 decimal places.

Total 31 marks. Allow about 31 minutes.

Exercise 3X  Exam-style questions

1
FCalculate the energy needed to warm 2 kg of copper by 10 °C. Write the number of joules.[2 marks]
2
PSA heater transfers 3600 J to 0.6 kg of iron. Calculate the temperature rise of the iron. Write the number in °C.[2 marks]
3
PSA 0.2 kg block of metal gets 1800 J and warms by 30 °C. Calculate its specific heat capacity. Write the number in J/kg °C.[2 marks]
4
PSA student uses a 12 V heater carrying 3 A for 200 s to heat a 1 kg block. The block warms by 8 °C. Calculate the specific heat capacity of the block. Write the number in J/kg °C.[3 marks]
5
PSA pupil heats 0.5 kg of water in a beaker with a 60 W heater for 5 minutes. The water warms by 8 °C. Calculate the energy the heater supplies, and the energy the water gains. Write two numbers in joules, separated by a comma (heater first).[3 marks]
6
RExplain why the result of the practical is too high if there is no insulation, and describe one change to the method that reduces this error. Accept any answer that says heat is lost to the surroundings, and names insulation or a lid.[3 marks]
7
PSA pupil heats a block of unknown metal with 9000 J. The block has a mass of 1 kg and warms by 25 °C. Calculate c, then identify the metal from this table: water 4200, aluminium 900, iron 450, copper 385. Write the metal name.[3 marks]
8
RDescribe how a student could find the specific heat capacity of a metal block, using a low-voltage heater, a thermometer, a power supply and insulation. Name the measurements and the equation. Accept any answer that uses E = V x I x t, measures mass and temperature rise, and uses c = E / (m x Δθ).[5 marks]
9
RA student says that water is the best material for a heat store because it is cheap. Evaluate this claim, using the specific heat capacity of water. Accept any answer that says the high specific heat capacity is the key property, and that cost is a secondary point.[4 marks]
10
PSA 4 kg block of metal is heated and its temperature rises by 15 °C. The energy supplied is 16200 J. Calculate the specific heat capacity of the metal, and explain whether the energy supplied equals the energy absorbed if some heat is lost. Write the value of c in J/kg °C.[4 marks]
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