Lesson Plan

• Describe how energy is absorbed during melting and boiling while temperature remains constant.
• Explain the role of latent heat of fusion and vaporisation in phase changes.
• Interpret temperature‑time graphs that show plateaus for melting and boiling.
• Calculate the energy required for a given mass to melt or boil using Q = mL.

• Projector and screen
• Whiteboard and markers
• Ice cubes and a kettle with water
• Thermometers
• Worksheet with sample calculations and graph tasks
• Calculator or classroom computers

Begin with a quick demonstration: place ice in a beaker and heat water in a kettle, asking students what they expect to happen to the temperature. Recall prior learning about heat, temperature, and kinetic energy. Explain that by the end of the lesson they will be able to describe why temperature plateaus during melting and boiling and predict the energy needed for these changes.

1. Do‑now (5'): Students answer a short quiz question on heat vs. temperature; teacher checks responses.
2. Mini‑lecture (10'): Explain phase changes, latent heat, and constant‑temperature plateaus using a projector diagram.
3. Guided demonstration (10'): Heat ice to melt and water to boil while recording temperature plateaus; students note observations.
4. Collaborative worksheet (12'): Groups calculate energy for melting 250 g ice and boiling 200 g water and complete a temperature‑time graph.
5. Concept check (8'): Quick exit questions via clickers or show of hands to gauge understanding.
6. Summary discussion (5'): Review key points and clarify any misconceptions.

Summarise that during melting and boiling the supplied energy breaks intermolecular bonds, keeping temperature steady, and that latent heat quantifies this energy. Students complete an exit ticket stating one real‑world example of each phase change. For homework, assign a set of problems requiring calculation of energy for different masses.