Specific Heat Capacity and Specific Latent Heat in Calculations · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Warming, melting and heater maths

Science · Energy · ages 15-17
Name ______________________   Date ____________

  1. A 50 W heater runs for 120 s. How much energy does it supply in joules?

    Answer: ______________

  2. A 50 W heater runs for 120 s. How much energy does it supply in joules?

    Answer: ______________

  3. Ice melting at 0 degrees keeps the same temperature until all of it has melted.

    Circle one:   True   False

  4. On a heating graph for ice to steam, what does a flat section mean?

    • Steady warming of a solid
    • Cooling back to room temperature
    • Melting or boiling

  5. 0.5 kg of ice at minus 20 warms to 0. Use c for ice = 2100. How much energy does this stage take?

    • 8400 J
    • 2100 J
    • 21000 J

  6. Some heater energy leaks to the surroundings, so the sample warms less than P x t predicts. True or false?

    Circle one:   True   False

  7. 0.5 kg of water warms by 10 C. Use c = 4200 J/kg/C. How much energy is needed in joules?

    Answer: ______________

  8. 0.5 kg of water warms by 10 degrees. Use c = 4200. How much energy is needed in joules?

    Answer: ______________

  9. A heater gives exactly power times time to the sample, since no heat ever leaks away.

    Circle one:   True   False

  10. 200 g of ice at minus 10 becomes water at 40. Which order of stages is right?

    • Melt, then warm ice, then warm water
    • Boil, then melt, then warm
    • Warm ice, melt it, then warm the water
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Warming, melting and heater maths W1-mt_GKNPAJgroW-s1

  1. 6000 · Energy is power times time: 50 x 120 = 6000 J.
  2. 6000 · Energy from a heater is power times time.
  3. True · Change of state takes m L with no temperature change.
  4. Melting or boiling · Flat means energy breaks bonds, not raises temperature: a change of state.
  5. 21000 J · Warming uses Q = m c delta T = 0.5 x 2100 x 20 = 21000 J.
  6. True · Lost heat warms the room, not the sample, so the rise falls short of P times t.
  7. 21000 · Q = m c delta T = 0.5 x 4200 x 10 = 21000 J.
  8. 21000 · Warming uses Q = m c delta T.
  9. False · Lost heat warms the room, not the sample, so the rise falls short.
  10. Warm ice, melt it, then warm the water · Chain the run in order: warm the solid, change its state, warm the liquid.
Worksheet · LightMySky