The shape of the lesson
By the end of the lesson, learners can
- Pour in energy, watch it warm: Change the material, the mass and the energy supplied, and read off the temperature rise.
- Energy, mass, temperature change: The equation ties together how much you heat, how much there is, and what it is made of.
- For energy: ΔE = m c Δθ.
- For c: c = ΔE / (m Δθ).
- Always work out the temperature change Δθ first, and include the mass.
One picture every idea returns to
The specific heat capacity c is the energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius. The energy transferred is E = mc times the change in temperature, measured in joules.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, How much heat to warm it.. Sand at the beach scorches your feet by noon while the sea stays cool. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Pour in energy, watch it warm | Change the material, the mass and the energy supplied, and read off the temperature rise. Project tab 1 of the lab (Specific heat capacity) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Energy, mass, temperature change | The equation ties together how much you heat, how much there is, and what it is made of. Model the worked example Worked example on the board, one line at a time. | Numbered Heads Together |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 16 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Energy, mass, temperature change, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Numbered Heads Together
Teams of four number off. Put up a question, give the team time to make sure every member can answer, then call a number: that student answers for the team, so nobody can leave the thinking to someone else.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Specific heat capacity is defined per kilogram, so always multiply by the actual mass. | And use the temperature change, not the final temperature: heating from 20 to 50 degrees Celsius is a change of 30, not 50. |
Specific heat capacity (E = mcΔθ): worksheet
6 questions, 16 marks. Written in the style of the papers; no past paper question is reproduced.
Define the specific heat capacity of a substance, and state its unit.
Calculate the energy needed to raise the temperature of 0.5 kg of water from 20 degrees C to 80 degrees C. The specific heat capacity of water is 4200 J/(kg degrees C).
A 0.5 kg block of metal is given 9000 J of energy and its temperature rises by 40 degrees C. Calculate the specific heat capacity of the metal.
A heater supplies 27 000 J of energy to 1.5 kg of aluminium, of specific heat capacity 900 J/(kg degrees C). Calculate the rise in temperature, assuming no energy is lost.
Water has a much higher specific heat capacity than most metals. Explain what this means in practice, and give one use that depends on it.
Describe an experiment using an electrical heater to measure the specific heat capacity of a metal block. State the measurements you would take and how you would use them.
Answer key and marking notes
- It is the energy needed to raise the temperature of 1 kg of the substance by 1 degree C (or 1 K). ✓
- Unit: J/(kg degrees C), joules per kilogram per degree Celsius. ✓
Δθ: 80 - 20 = 60 degrees C
ΔE = m c Δθ = 0.5 x 4200 x 60ΔE = 126 000 J (126 kJ)
- c = ΔE / (m Δθ) = 9000 / (0.5 x 40)
c = 9000 / 20
c = 450 J/(kg degrees C)
- Δθ = ΔE / (m c) = 27000 / (1.5 x 900)
Δθ = 27000 / 1350
Δθ = 20 degrees C
- It takes a lot of energy to change water's temperature, so water heats up and cools down slowly. ✓
- Used as a coolant (for example in car engines) or to carry heat in central heating systems. ✓
- Measure the mass of the block, and place an electrical heater (and a thermometer) into it. ✓
- Measure the energy supplied by the heater and the rise in temperature it produces. ✓
- Calculate c = energy supplied / (mass x temperature rise). ✓
7 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
How much energy is needed to raise the temperature of 0.50 kg of water by 20 °C? Take c = 4200 J/(kg °C).
- A2100 J
- B4200 J
- C42 000 J
- D84 000 J
A 2.0 kg metal block gains 24 000 J of energy and its temperature rises by 30 °C. What is its specific heat capacity?
- A400 J/(kg °C)
- B800 J/(kg °C)
- C12 000 J/(kg °C)
- D1 440 000 J/(kg °C)
10 800 J is supplied to 0.40 kg of a metal of specific heat capacity 900 J/(kg °C). What is the temperature rise?
- A3.0 °C
- B30 °C
- C27 °C
- D300 °C
6300 J of energy raises the temperature of a quantity of water by 5.0 °C. Taking c = 4200 J/(kg °C), what is the mass of the water?
- A0.030 kg
- B0.30 kg
- C3.0 kg
- D30 kg
A 50 W heater warms a 0.25 kg metal block for 120 s. Assuming no energy is lost and c = 480 J/(kg °C), what is the temperature rise of the block?
- A5.0 °C
- B25 °C
- C50 °C
- D100 °C
Equal masses of water and cooking oil are each given the same amount of energy. Water has the higher specific heat capacity. Which heats up more?
- AThe oil, because a lower specific heat capacity means a larger temperature rise for the same energy.
- BThe water, because it has the higher specific heat capacity.
- CBoth rise by the same amount.
- DNeither changes temperature.
A substance has a specific heat capacity of 4200 J/(kg °C). What does this value mean?
- A4200 J raises the temperature of 1 kg of the substance by 1 °C.
- B4200 J raises the temperature of any mass by 1 °C.
- C4200 J melts 1 kg of the substance.
- D4200 J raises 1 kg of the substance to 1 °C.
Quiz key
E = mcΔθ = 0.50 × 4200 × 20 = 42 000 J. Option D forgets the factor of 0.50 (uses the full 4200 × 20 doubled); B ignores the temperature change.
c = E ÷ (mΔθ) = 24 000 ÷ (2.0 × 30) = 400 J/(kg °C). Option C divides by the mass only, forgetting the temperature change.
Δθ = 10 800 ÷ (0.40 × 900) = 10 800 ÷ 360 = 30 °C. Option A divides by 10 times too much; D multiplies instead of dividing somewhere.
m = E ÷ (cΔθ) = 6300 ÷ (4200 × 5.0) = 6300 ÷ 21 000 = 0.30 kg. Option C divides by c only and forgets the temperature change.
E = Pt = 50 × 120 = 6000 J, then Δθ = E ÷ (mc) = 6000 ÷ (0.25 × 480) = 6000 ÷ 120 = 50 °C. Option B forgets to multiply the power by the time correctly.
From Δθ = E ÷ (mc), the substance with the smaller c has the bigger temperature rise, so the oil heats up more. Water's high specific heat capacity means it needs more energy per degree (ruling out B).
Specific heat capacity is the energy needed to raise 1 kg by 1 °C, so 4200 J does that for 1 kg of this substance. Option B drops the per-kilogram part; C describes latent heat, not specific heat capacity.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.