Melt and Boil

Put a block of ice on a heater and watch what happens to the temperature and to the particles as it melts, warms up and boils.

Speed up time
Temperature
-20.0 °C
State
Solid (ice)
Heating time
0 s
Heat put in
0 kJ

The maths, live

Ice warming Q = m × c × ΔTQ = 1.0 × 2100 × 0.0 = 0.0 kJ
Heat from heater Q = P × tQ = 2000 × 0 = 0 kJ

Why does the temperature stop rising while the ice melts? Which takes longer: melting or boiling?

How it works

Warming a substance takes energy: Q = m × c × ΔT, where c is the specific heat capacity. Water has a big one (4186 J per kg per °C), so it takes a lot of energy to warm up. Ice and steam need only about half as much per degree.

While ice melts, the temperature stays at 0 °C even though the heater is still on. The energy is used to break the bonds holding the particles in place. This is latent heat: Q = m × L. Boiling at 100 °C takes nearly seven times more energy than melting, because the particles must be pulled right apart to fly off as a gas.

Try this

  1. Which flat part of the graph lasts longer, melting or boiling? Why?
  2. Double the mass of ice. What happens to the time it takes?
  3. Watch the particles: how do they move in ice, in water and in steam?