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Leaving Cert Physics: Latent heat

How often Latent heat comes up on the Physics papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 9 of the last 10 Ordinary Level papers, most recently in 2026. banker

June 2027 is the first exam on the new Physics course. These come from the 2016–2026 papers, so read them as a guide.

Latent heat, Higher Level(8 marks)

Quick ones on Latent heat.

(a)Unit of specific latent heat?
  1. J kg⁻¹ K⁻¹
  2. J kg⁻¹
  3. J
(b)Energy needed to melt 0.50 kg of ice at 0 °C (l = 3.3 × 10⁵ J kg⁻¹)?
  1. 3.3 × 10⁵ J
  2. 6.6 × 10⁵ J
  3. 1.65 × 10⁵ J
(c)Why does sweating cool the body?
  1. Evaporating sweat takes its latent heat from the body
  2. Sweat is a very good conductor of heat
  3. Sweat has a very low specific heat capacity
Show the answers

(a) J kg⁻¹

(b) 1.65 × 10⁵ J

(c) Evaporating sweat takes its latent heat from the body

Your turn: Higher Level questions on Latent heat.

Higher Level

Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q4
2025Q10
2024Q3
2023Q4
2022Not asked
2021Q9
2019Q3
2018Q8
2017Q3
2016Q7

Links open the State Examinations Commission’s paper for that year.

More Latent heat questions

Latent heat, 3 marks

Define specific latent heat.

  1. The energy needed to raise the temperature of 1 kg of a substance by 1 K without a change of state
  2. The total energy needed to melt or boil a substance, whatever its mass
  3. The energy needed to change the state of 1 kg of a substance without any change in temperature
Show the answer

The energy needed to change the state of 1 kg of a substance without any change in temperature

Q = ml, unit J kg⁻¹. While melting or boiling, the energy breaks bonds, so the thermometer reading does not change.

Ordinary Level

Asked on 9 of the last 10 Ordinary Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q4
2025Q4
2024Q9
2023Q3
2022Q8
2021Q4
2019Q2
2018Not asked
2017Q12(b)
2016Q9

Links open the State Examinations Commission’s paper for that year.

More Latent heat questions

Latent heat, 2 marks

What happens to the temperature of ice while it is melting?

  1. It rises steadily
  2. It falls
  3. It stays the same
Show the answer

It stays the same

The energy taken in (latent heat) is used to change the state, not to raise the temperature. Melting ice stays at 0 °C.

Latent heat, 3 marks

Why does steam at 100 °C cause a worse burn than boiling water at 100 °C?

  1. Steam conducts heat much better than water does
  2. Steam gives out its latent heat as it condenses on the skin
  3. Steam is at a much higher temperature than the boiling water
Show the answer

Steam gives out its latent heat as it condenses on the skin

Both start at 100 °C, but steam first gives out a large amount of latent heat as it turns to water on the skin.

Latent heat, 2 marks

What is latent heat?

  1. Heat taken in or given out when a substance changes state, with no change in temperature
  2. Heat that raises the temperature of a substance without changing its state
  3. Heat lost by radiation from a hot substance as it cools down to room temperature
Show the answer

Heat taken in or given out when a substance changes state, with no change in temperature

While ice melts or water boils, the energy goes into changing the state, not raising the temperature. The same energy comes back out when it changes back.

Other Physics topics

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