Brainlag PlusThe energy to melt or boil a substance without changing its temperature, E = mL, and finding L with a heater.
Energy to change state
The specific latent heat of a substance is the energy needed to change the state of 1 kg of it with no change in temperature.
energy for a change of state = mass × specific latent heat
E = m L
Energy in J, mass in kg, L in J/kg (given on the equation sheet). Latent heat of fusion: solid to liquid. Latent heat of vaporisation: liquid to gas.
- Melt 0.5 kg of ice at 0 °C; L = 334 000 J/kg
- E = 0.5 × 334 000
- E = 167 000 J
The rest of this lesson and its 9 practice questions are in Plus.
Screen 1 of 4, free to read.
- 9 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards