Evaporation and Condensation

Overview

In this fifth lesson of the unit, students investigate evaporation and condensation as changes of state. They will observe water heating and steam cooling, then use particle models to explain what is happening to particles during liquid-to-gas and gas-to-liquid processes.

Learning intentions

• Students will investigate evaporation and condensation using a simple, safe scientific method.
• Students will describe observable properties of liquids and gases using particle motion and arrangement models.
• Students will use scientific language (evaporation, condensation, steam, liquid, gas).
• Students will record observations accurately and identify possible sources of error.

Success criteria

• I can explain how particles move during evaporation (liquid to gas).
• I can explain how particles behave during condensation (gas to liquid).
• I can use a particle model and scientific words to describe both changes of state.
• I can record my measurements/observations clearly and state one reason my results might differ from others.

Curriculum links

• Science: explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• Science: plan and conduct repeatable investigations, including fair-test thinking, risk awareness, and safe equipment use.
• Science: use equipment to observe, measure and record data with reasonable precision, using digital tools as appropriate.
• Science: compare methods and findings with others, recognise possible sources of error, and draw reasoned conclusions.

Lesson structure (80 minutes)

1. 0–8 min · Hook and prior knowledge check. Teacher shows two quick visuals: a drying puddle and droplets forming on a cold drink bottle. Students quick-write: “What changed—solid, liquid, or gas?” then share one idea with a partner.
2. 8–18 min · Direct teach: particle model for evaporation/condensation. Teacher uses role-play or a simple particle diagram:

• Evaporation: particles in a liquid move faster, spread out, become gas.
• Condensation: gas particles cool, slow down, come together, become liquid. Students complete a labelled mini whiteboard sketch of a particle model for each process.

3. 18–30 min · Investigation setup and safety. Teacher explains and demonstrates the method (two-station approach):

• Station A (evaporation): observe water in a shallow container over time.
• Station B (condensation): steam produced from hot water is directed to a cooler surface (e.g., underside of a lid held over steam, or a cold metal/plastic surface) to create droplets. Students listen for variables to control (same container size, same starting water volume, same observation times) and repeat key safety rules (eye protection, careful handling, no touching hot surfaces). Students set up recording tables.

4. 30–52 min · Conduct investigation (repeatable measurements). In groups, students run both stations in rotation. Teacher prompts: measure/record what you can (e.g., time for visible change; approximate droplet amount; temperature if available; water level/line marks if safe). Students record at set intervals and add one diagram of what they see (not just words).
5. 52–60 min · Data share and fair test check. Groups compare their results briefly with another group. Teacher asks: “Did we change only one thing? What might have affected the results?” Students circle one possible source of error (e.g., different starting volume, uneven heating, observation delay).
6. 60–70 min · Explanation building: “Particle story”. Students use sentence frames to explain both processes:

• “During evaporation, particles in the liquid ___ and spread out because ___.”
• “During condensation, gas particles ___ when they cool, so they ___ together to form a liquid.” Students match their explanations to particle models they created earlier.

7. 70–78 min · Whole-class synthesis with teacher modelling. Teacher selects one or two group examples and models how to upgrade language (e.g., from “water disappears” to “particles escape from the surface as a gas”). Students vote on which explanation best matches evidence and particle behaviour.
8. 78–80 min · Exit ticket. Students answer: “Explain evaporation and condensation using a particle model and scientific words. Include one reason your observations might differ from another group.”

Resources

• Safety goggles for each student
• Shallow containers and measuring jugs/cups
• Water source and kettle or hot plate (teacher-handled if required by school policy)
• Lids, tray/towel for steam station, tongs/heat-proof gloves for teacher or designated role
• Cold surface option (e.g., chilled metal spoon or ice-filled container under supervision)
• Timer/stopwatch
• Data recording sheets (tables for observations and times)
• Markers/labels for starting water levels
• Digital device for photo evidence (optional) and/or class charting template
• Particle model printouts or mini cards for evaporation/condensation

Assessment

• Observation checklist during investigations: correct use of measurement/recording and safe practices.
• Formative questioning: “What evidence do you have?” “What does your particle model suggest?”
• Exit ticket at the end: accuracy of particle explanations and use of scientific language.

Differentiation

• Support for students needing scaffolding: sentence starters, word bank, and partially completed particle model diagrams.
• Support for EAL learners: allow drawing plus key vocabulary; provide model sentences and clarify pronunciation of “evaporation/condensation.”
• Extension for confident students: ask them to quantify more closely (e.g., compare two evaporation times with different container widths) while keeping the method repeatable.
• Managing diversity in group roles: assign clear roles (timekeeper, recorder, safety monitor, materials controller) so all students contribute.