Specific Latent Heat Flashcards

All 6 cards in this deck

What is the equation for the thermal energy needed for a change of state?

thermal energy $=$ mass $\times$ specific latent heat
$Q = m \times L$

What are the units of specific latent heat?

J/kg (joule per kilogram).

Which changes of state use the specific latent heat of fusion?

Melting and freezing (solid ↔ liquid).

Which changes of state use the specific latent heat of vaporisation?

Boiling/evaporating and condensing (liquid ↔ gas).

What are the steps to calculate the thermal energy needed to melt a mass of ice?

e.g. $0.5$ kg of ice at $0$ °C, $L = 3.34 \times 10^5$ J/kg

1. Write $Q = m \times L$ with mass in kg
2. Substitute: $Q = 0.5 \times 3.34 \times 10^5$
3. $Q = 1.67 \times 10^5$ J

What are the steps to calculate a specific latent heat from energy and mass?

e.g. $4.6$ MJ turns $2$ kg of boiling water into steam

1. Write $Q = m \times L$
2. Rearrange: $L = Q \div m$
3. Substitute: $L = 4.6 \div 2 = 2.3$ MJ/kg