Specific latent heat: melting ice and boiling water sim
Melt ice with an immersion heater beside a control funnel, or boil water on a balance, record the joulemeter and the masses each minute, and find the specific latent heat from your graph.
Thermal properties: latent heat · covers the O-Level, GCSE topic
What the sim shows
Specific latent heat is the energy needed to change the state of 1 kg of a substance with no change in temperature: L = E ÷ m. While the ice melts it stays at 0 °C, and while the water boils it stays at 100 °C: the energy goes into changing the state, not into raising the temperature. The heater runs from 12 V at 4 A, so it supplies 48 J every second; the joulemeter adds this up. Melting: the room melts ice in both funnels at about the same rate (1.2 g a minute here), so the heater's ice is the heated funnel's water minus the control funnel's water. In 5 minutes the heater supplies 14400 J and melts about 41.4 g, so L comes out near 348 kJ/kg against the data-book 334 kJ/kg: a few per cent of the heater's energy warms the glass and the air. Boiling: the balance reading falls as water boils away; heat lost from the beaker's sides and top (about 6 W) means less water boils than the energy could boil, so L comes out high, near 2.58 × 10⁶ J/kg against the data-book 2.26 × 10⁶ J/kg. A top-pan balance measures weight (W = mg, g = 10 N/kg) and shows it as mass. Time moves only when you press Wait 1 minute. Model limits: the ice is at 0 °C and dripping steadily from the start; the water is already boiling; the losses are set values; drops land in small bursts, so each balance reading can be up to 0.1 g off.
- Joulemeter: the energy E the heater has supplied
- Control funnel: the ice the room melts, with no heater
- Top-pan balance: the melt water, or the water left
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