Science · Year 2 · Mixing and Moving Materials · Term 1

Evaporation and Condensation

Students will explore how water changes from liquid to gas (evaporation) and gas to liquid (condensation).

• ACARA Content Descriptions
• AC9S2U04

About This Topic

Year 2 students examine evaporation, where liquid water changes to gas through heating or wind, and condensation, where gas turns back to liquid upon cooling. They connect these to real-world examples, such as puddles shrinking on sunny days or droplets forming on cold drink glasses. Through observation and simple tests, students answer key questions about disappearing puddles, glass condensation, and modelling these water cycle stages.

This topic supports AC9S2U04 by showing how everyday materials change state reversibly under different conditions. Students develop skills in fair testing, data recording, and explaining observations, which strengthen scientific thinking for later units on mixtures and forces.

Active learning suits evaporation and condensation perfectly since the processes respond quickly to classroom conditions. Students gain confidence predicting outcomes, like faster drying in wind, then verify through group trials. Hands-on models and shared reflections turn fleeting observations into lasting understanding of matter changes.

Key Questions

1. Analyze how puddles disappear on a sunny day.
2. Explain the process of condensation on a cold glass.
3. Construct a model to demonstrate the water cycle's evaporation and condensation stages.

Learning Objectives

• Explain how heat causes liquid water to change into water vapor during evaporation.
• Identify the role of cooling in transforming water vapor back into liquid water through condensation.
• Construct a model that demonstrates the processes of evaporation and condensation within a closed system.
• Analyze why puddles disappear more quickly on a warm, windy day compared to a cool, still day.

Before You Start

Observing and Describing Materials

Why: Students need to be able to observe changes in materials and describe what they see to understand evaporation and condensation.

Basic Needs of Living Things

Why: Understanding that living things need water provides context for the importance of the water cycle, including evaporation and condensation.

Key Vocabulary

Evaporation	The process where liquid water turns into a gas, called water vapor, usually when heated or exposed to wind.
Condensation	The process where water vapor in the air cools down and changes back into liquid water, forming droplets.
Water Vapor	Water in its gas form, which is invisible and mixes with the air.
Water Cycle	The continuous movement of water on, above, and below the surface of the Earth, including evaporation and condensation.

Watch Out for These Misconceptions

Common Misconception

Evaporated water is gone forever.

What to Teach Instead

Water changes to invisible gas but can return via condensation. Experiments like bag models show vapour reforming as droplets, helping students revise ideas through repeated observation and peer talk.

Common Misconception

The sun drinks or sucks up water.

What to Teach Instead

Heat from sun provides energy for molecules to escape as gas. Comparing drying in sun versus shade reveals energy role; group predictions and measurements correct magical thinking.

Common Misconception

Condensation only happens outside.

What to Teach Instead

It occurs anywhere gas meets cold surfaces, like glasses or lids. Classroom demos with ice and steam make it immediate; students test variables to see conditions matter.

Active Learning Ideas

Outdoor Hunt: Puddle Measurements

Students find school puddles, outline with chalk, and measure length and width at start, midday, and end. Note sun, wind, and shade effects in notebooks. Groups compare data to identify patterns.

30 min·Small Groups

Stations Rotation: Evaporation Conditions

Prepare trays of water: one in sun, one shaded, one fanned, one still. Rotate groups every 10 minutes to measure water levels hourly. Predict and record which dries fastest.

45 min·Small Groups

Condensation Bags: Cooling Vapour

Fill clear plastic bags halfway with hot water, seal, and tape to windows. Observe droplets forming inside as vapour condenses. Wipe and repeat with ice inside to speed it up; draw changes.

20 min·Pairs

Whole Class Demo: Glass Mystery

Place cold glasses amid classroom steam from hot water bowls. Students predict and watch condensation form, then wipe and retest. Discuss why it happens on cold surfaces.

25 min·Whole Class

Real-World Connections

• Clothes dryers use heat and airflow to speed up the evaporation of water from wet laundry, making clothes dry faster.
• Window cleaners observe condensation forming on cold window panes during winter. This happens when warm, moist indoor air touches the cooler glass surface.
• Meteorologists study evaporation from oceans and lakes to predict humidity levels and potential rainfall in different regions.

Assessment Ideas

Quick Check

Show students a glass of ice water. Ask: 'What do you see forming on the outside of the glass? Where did that water come from?' Record their answers to gauge understanding of condensation.

Exit Ticket

Provide students with two scenarios: 'A puddle on a sunny, windy day' and 'A puddle on a cool, cloudy day'. Ask them to write one sentence explaining which puddle will disappear faster and why, using the terms evaporation and condensation.

Discussion Prompt

Pose the question: 'Imagine you are a water droplet in a puddle. Describe what happens to you on a hot day and then what happens when the sun goes down.' Encourage students to use scientific vocabulary in their explanations.

Frequently Asked Questions

How do you demonstrate evaporation for Year 2?

Use shallow dishes of water under different conditions: sun, shade, fan, covered. Students measure daily with rulers and predict changes. This builds evidence-based explanations as they track mass loss over a week, linking to puddle questions.

What activities show condensation clearly?

Seal hot water in zip-lock bags or place cold metal spoons over steaming cups. Droplets form visibly in minutes. Students time appearance and test with warmer/cooler surfaces, reinforcing cooling causes change.

How can active learning help students understand evaporation and condensation?

Direct experiments let students manipulate variables like heat and wind, observing rapid changes that match predictions. Small group rotations ensure all participate, while class charts of results reveal patterns. Discussions connect personal evidence to models, deepening retention over passive lessons.

How does this link to the water cycle?

Focus on evaporation from surfaces and condensation in clouds. Build simple models with bags or jars to cycle water repeatedly. This previews full cycle, answering standards by showing reversible states in nature.