Phase Changes & Latent Heat
📋 What it is
Melting and boiling absorb energy without raising temperature — that hidden energy is latent heat.
🗣️ Coach says
When ice melts or water boils, its temperature holds STEADY even as you add heat. That energy isn’t lost — it goes into breaking the bonds between particles to change state. It’s called latent ("hidden") heat, and it’s why sweating cools you: evaporating water carries heat away.
🧠 Memory hook
During a phase change, temperature holds steady — energy goes into changing state (latent heat).
😂 Giggle
Why did the steam feel so free?
Because it had just evaporated all its problems!
😲 Whoa!
Sweating cools you because evaporating water steals latent heat from your skin — the same reason a breeze feels cold when you’re wet.
✅ Quick check: Why does the temperature of boiling water stay at 100 °C even as you keep heating it?
Say your answer out loud first — then reveal.
The added energy goes into changing water to steam (latent heat), not into raising temperature.
During a phase change, energy breaks bonds instead of warming.
🪄 Trick question: Does adding heat always raise a substance’s temperature?
Careful — think it through, then reveal.
No — during melting or boiling the temperature stays flat while the energy changes the state.
Latent heat changes phase without changing temperature.
🧪 Try it! (2 minutes)
Put a thermometer in ice water and watch it hold near 0 °C while the ice melts, then rise after.