Specific Latent Heat Flashcards

All 6 cards in this deck

What is the specific latent heat of a substance?

The amount of energy required to change the state of one kilogram of the substance with no change in temperature.

Which change of state does specific latent heat of fusion refer to?

Solid to liquid (melting).

Which change of state does specific latent heat of vaporisation refer to?

Liquid to vapour (boiling/evaporating).

True or false? For a given substance, the specific latent heat of fusion and the specific latent heat of vaporisation are equal.

False. They are different values; for water the specific latent heat of vaporisation is much larger.

What are the steps to calculate the energy needed for a change of state?

e.g. melt 2 kg of ice, $L = 340\,000$ J/kg

1. Write $E = mL$, mass in kg.
2. Substitute: $E = 2 \times 340\,000$
3. Evaluate: $E = 680\,000$ J

What are the steps in an experiment to measure the specific latent heat of fusion of water?

e.g. 3400 J of energy melts 0.010 kg of ice

1. Place an immersion heater in a funnel of crushed ice, collecting melted water in a beaker on a balance.
2. Measure the energy supplied $E$ (joulemeter, or power × time) and the mass $m$ of water melted.
3. Calculate $L = \dfrac{E}{m} = \dfrac{3400}{0.010} = 340\,000$ J/kg