Changes of State: Evaporation and Condensation

Students learn best when they can connect abstract concepts to their own experiences. For changes of state, hands-on exploration helps them see invisible processes like evaporation and condensation in action, making the science feel real and memorable.

• Primary 4
• Science
• 4 activities
• 20 min–45 min

Learning Objectives

1. Compare the rate of evaporation under different conditions of temperature, surface area, and air movement.
2. Explain the process of condensation using the particle model of matter.
3. Differentiate between evaporation and boiling based on observable characteristics and temperature.
4. Predict the formation of dew and clouds based on changes in temperature and water vapor.
5. Analyze the role of evaporation and condensation in everyday phenomena like drying clothes or fogged mirrors.

Inquiry Circle

⏱ 45 min·Small Groups

Experiment Rotation: Evaporation Factors

Prepare trays with equal water volumes: vary temperature (warm vs room), surface area (wide vs narrow), and airflow (fan vs still). Groups test one station, measure mass loss over 10 minutes, and graph results. Rotate stations and compare data class-wide.

Prepare & details

Analyze the factors that influence the rate of evaporation.

Facilitation Tip: During Experiment Rotation: Evaporation Factors, circulate with a timer to ensure students record water levels at exact intervals to compare results fairly.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 20 min·Pairs

Demo Pairs: Condensation Observation

Pairs breathe on cold metal spoons or plastic bags from freezer to see droplets form. Predict what happens when warming the surface, then test and draw particle diagrams. Discuss links to cloud formation.

Prepare & details

Explain how condensation leads to the formation of clouds and dew.

Facilitation Tip: For Demo Pairs: Condensation Observation, pair students to share predictions before testing so quiet thinkers get to speak first.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 30 min·Pairs

Compare Task: Boiling vs Evaporation

In pairs, observe a pan of simmering water and a dish of water at room temperature over 15 minutes. Note where changes occur and measure mass changes. Class shares findings to clarify differences.

Prepare & details

Differentiate between boiling and evaporation.

Facilitation Tip: In Compare Task: Boiling vs Evaporation, provide identical thermometers so students see the temperature difference clearly when comparing the two processes.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 35 min·Whole Class

Whole Class: Dew Point Hunt

Students predict and check surfaces around school for morning dew, noting temperatures. Collect data on class chart and explain using condensation ideas. Connect to weather reports.

Prepare & details

Analyze the factors that influence the rate of evaporation.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Teaching This Topic

Start with familiar examples students have seen, like wet clothes drying or mirrors fogging, to build prior knowledge. Avoid lecturing about particle theory upfront; let students discover the patterns through experiments. Research shows that guided inquiry works best when students first make predictions, then test them, and finally explain their findings. Model scientific language during discussions but let students try using it themselves in small groups.

What to Expect

By the end of these activities, students should clearly explain how temperature, surface area, and moving air affect evaporation, and how condensation forms when gas particles lose energy. They should also describe the water cycle in terms of these two processes.

Watch Out for These Misconceptions

Common Misconception

During Experiment Rotation: Evaporation Factors, watch for students assuming boiling is required for evaporation. Have them compare water loss in dishes at room temperature, warm water, and boiling water, then measure and discuss the differences in small groups.

What to Teach Instead

Have students measure and compare water loss in dishes at room temperature, warm water, and boiling water. Ask them to calculate the volume lost and discuss why evaporation happens at the surface even without bubbles.

Common Misconception

During Demo Pairs: Condensation Observation, watch for students believing condensation only occurs in very cold environments. After the breath-on-glass demo, ask them to predict where else condensation might form indoors and test their ideas with classroom thermometers.

What to Teach Instead

After the breath-on-glass demo, ask students to predict where else condensation might form indoors. Provide thermometers to test surfaces like windows or metal objects, and discuss why temperature differences matter.

Common Misconception

During Experiment Rotation: Evaporation Factors, watch for students thinking evaporated water is gone forever. After sealing jars with water, have students observe condensation forming on the jar lids over time and explain where the 'missing' water went.

What to Teach Instead

After sealing jars with water, have students observe condensation forming on the lids over time. Ask them to trace the water's journey from liquid to gas to liquid again, using their observations to correct the misconception.

Assessment Ideas

Quick Check

After Experiment Rotation: Evaporation Factors, present students with three identical containers of water. Ask them to predict which will evaporate fastest if one is in a sunny spot, one in a shady spot, and one with a fan. Have them record their predictions and reasons, then compare their answers to the actual results.

Exit Ticket

During Demo Pairs: Condensation Observation, give students an index card to draw a simple diagram showing one factor that speeds up evaporation and one factor that causes condensation. Ask them to label their diagrams clearly and hand them in before leaving.

Discussion Prompt

After the Compare Task: Boiling vs Evaporation, pose the question: 'Imagine you are a water droplet. Describe your journey from being part of a puddle to becoming part of a cloud, explaining the changes of state you experience.' Facilitate a class discussion where students share their 'water droplet stories' and provide feedback on their use of scientific terms.

Extensions & Scaffolding

• Challenge students who finish early to design a test for how humidity affects evaporation rates and present their method to the class.
• For students who struggle, provide a word bank with key terms like 'energy', 'surface area', and 'condensation' to support their explanations during the dew point hunt.
• Deeper exploration: Ask students to research how changes of state are used in real-world engineering, such as in refrigeration systems or desalination plants, and present findings to the class.

Key Vocabulary

Evaporation	The process where a liquid turns into a gas (water vapor) when it absorbs enough energy. This happens at the surface of the liquid.
Condensation	The process where a gas (water vapor) turns back into a liquid when it loses energy. This forms tiny water droplets.
Water Vapor	Water in its gaseous state. It is invisible and present in the air.
Particle Model	A way to visualize matter as being made up of tiny particles that are always moving. The movement and spacing of these particles explain the state of matter.