Engineering Evaporation

Overview

Lesson 6 of 8 continues the unit on states of matter by linking particle ideas about gases and evaporation to a practical engineering challenge. Students generate, compare, and refine solutions to reduce evaporative loss from local water bodies.

Learning intentions

Students will be able to:

• explain how particles in different states help explain why water evaporates into the air
• propose and justify engineering solutions to reduce evaporation from a reservoir
• plan a fair, repeatable investigation to compare the effectiveness of two approaches
• recognise possible sources of error and use evidence to draw a reasoned conclusion

Success criteria

“I can…”

• describe evaporation as water changing from liquid to gas and relate it to particle motion
• name at least two realistic engineering options and explain how each might reduce evaporation
• create an investigation plan that controls key variables and repeats measurements
• compare results to decide which solution is most supported by evidence

Curriculum links

• AC9S5U04: explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles (linked to evaporation)
• AC9S5I02: plan and conduct repeatable investigations, including variables, controlling a fair test, risks, and safe equipment use
• AC9S5I05: compare methods/findings, identify possible sources of error, and draw reasoned conclusions from evidence
• AC9S5H02: investigate how scientific knowledge is used to identify problems, consider responses, and make decisions (environmental stewardship of water resources)

Lesson structure (80 minutes)

1. 0–10 min · Hook: “What makes water disappear?” Teacher shows a simple scenario: a reservoir in hot weather with visible water level drop; students quick-write the cause in one sentence using the words liquid and gas. Students use a “thumbs-up if you agree” discussion: which solutions seem most likely and why.

2. 10–20 min · Particle model revisit (evaporation focus) Teacher leads a role-play: students act as particles in a liquid (close together), then “heat up” and spread out as gas (moving more freely). Students turn and talk: What particle change is happening during evaporation, and how might evaporation be slowed?

3. 20–35 min · Engineering challenge brainstorming Teacher displays the challenge: “Design an evaporation-reduction idea for a local water body.” Emphasise environmental stewardship and practical constraints (cost, maintenance, habitat impact). Students in groups brainstorm 3–4 options (e.g., shade/cover, wind barrier, airflow control, surface film, increased insulation) and record one possible “why it works” explanation in terms of slowing evaporation.

4. 35–55 min · Plan a fair test (mini investigation design) Teacher provides a planning template: question, hypothesis, variables (changed/measured/controlled), method steps, repeat counts, and safety/risk check. Students choose two options to test in the classroom using provided materials and complete a clear plan. Teacher checks plans against fair-test rules (only one key variable changes, same container size/amount, consistent placement and timing).

5. 55–70 min · Conduct trial + measure Teacher models measurement technique (e.g., mark starting water level, same time interval, read at eye level). Students run one short trial (or begin setup for the next lesson) and record data in a table (time, starting level, ending level, calculated change). Teacher circulates to ensure controlled conditions.

6. 70–80 min · Evidence talk + exit ticket Teacher prompts: “Which option should we expect to lose less water and why—using particle ideas?” Students complete an exit ticket: one sentence identifying the evidence they collected, one source of possible error, and one improvement for the next test.

Resources

• Evaporation scenario cards (hot, windy, shaded, calm conditions)
• Role-play particle cards or name tags (liquid particles / gas particles)
• Group planning template (question, variables, method, repeats, risks)
• Measuring tools: ruler or marked pipettes/cylinders, stopwatch/timer
• Containers (same size for fairness), water, trays/bench protection
• Materials for proposed solutions (sample covers, shade card, small screens, fan/blower if available under safety rules, labels)
• Data table sheets, pencils, markers
• Safety checklist prompt (handling liquids, electrical equipment if used)

Assessment

• Formative checks during discussion: student explanations linking liquid-to-gas and particle motion to evaporation
• Teacher review of each group’s investigation plan for fair-test variables and controlled conditions
• Exit ticket: evidence referenced, at least one possible error identified, and one next-step improvement proposed

Differentiation

• Scaffold for support: provide sentence starters (“I think evaporation is faster when… because particles…”; “In our test, we will keep ___ the same.”)
• Support for planning: offer a partially completed variables table for students who need it
• Extension for advanced learners: require an additional justification that considers environmental trade-offs (e.g., covers might affect sunlight/organisms; barriers might change airflow differently)
• EAL/SEN supports: allow oral rehearsal before writing; use visuals for variable labels (changed/measured/controlled) and pictorial risk checklist

Extension (optional)

• Advanced inquiry prompt: “Design a second fair test to compare two ‘shade’ designs only, while keeping wind and temperature constant as much as possible.”