Evaporation Exploration

Curriculum Area and Level

Science – Key Stage 2 (Year 4 & Year 5 Students)
Relevant to the following UK National Curriculum objectives:

• "Observe that some materials change state when they are heated or cooled, and measure or research the temperature at which this happens in degrees Celsius (°C)."
• "Identify the part played by evaporation and condensation in the water cycle and associate the rate of evaporation with temperature."

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Lesson Outcomes

By the end of the 60-minute lesson, students will:

1. Understand what evaporation is and how it contributes to the water cycle.
2. Observe evaporation through a practical experiment and record their findings.
3. Identify factors like temperature, air movement, and surface area that affect the speed of evaporation.

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Materials Needed

• 4 flat, shallow trays (one for each group)
• Water (200ml per tray)
• Kettles or warm water in containers (pre-prepared by teacher for safety)
• Stopwatch or timer
• Hairdryers (optional, for demonstration only - teacher-led to ensure safety)
• Camera or tablets (for students to document the process, optional)
• Whiteboard and markers
• A2 chart paper for group work
• Paper towels or cloths for cleaning up

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Lesson Structure

1. Hook: Setting the Scene (10 minutes)

Objective: To spark curiosity and engagement by introducing evaporation.

1. Teacher Panic Performance: Begin by walking into the classroom holding a soaked paper towel. Dramatically exclaim, "Oh no, my towel is soaked – but I don’t want it to stay wet! What if it never dries?"
2. Ask the students: What happens when we leave something wet out? Where does the water go?
3. Draw a quick cartoon sun and puddle on the whiteboard. Elicit ideas and introduce the word evaporation. If possible, visually exaggerate the word on the board (e.g., making it colourful, with sunbeams).
4. Quickly preview the experiment: "Today, we’re going to become scientists to investigate evaporation and figure out how to ‘dry’ water even faster!"

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2. Direct Instruction: The Science of Evaporation (10 minutes)

Objective: To explain evaporation in simple, age-appropriate terms, linking it to the water cycle.

1. Mini-Demo on Hand: Sprinkle a few drops of water on your hand. Blow on it gently. Ask: What just happened? Explain that evaporation is when water changes from liquid to gas, moving into the air.
2. Heat and Energy: Use a quick analogy: “Have you seen steam rise from a kettle or hot cup of tea? That’s water getting extra heat energy and turning into vapour!”
3. Link to the Water Cycle: Revisit the first lesson’s diagram of the water cycle briefly, pointing out evaporation as the "starting point" where water leaves rivers, oceans, and puddles.
4. Visual Aid: Draw water molecules on the whiteboard to show how heat makes them "excited" and spread apart.

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3. Guided Experiment (30 minutes)

Objective: To conduct an evaporation experiment and highlight factors affecting evaporation rates.

Step 1: Setting Up (5 minutes)

1. Divide the class into 4 mixed-ability groups.
2. Provide each group with a flat tray and 200ml of water. Explain that they will leave their trays in different conditions to see how quickly water "disappears."
3. Assign these conditions to the groups:
   • Group 1: Tray placed in sunlight (near a safe, sunny window).
   • Group 2: Tray placed in shade.
   • Group 3: Tray placed near a fan or hairdryer (controlled flow).
   • Group 4: Tray stirred gently every 2 minutes.

Step 2: Observation (10 minutes)

1. As students observe, guide them in timing (e.g., every 2 minutes) and recording any physical signs of water levels changing. Encourage them to use descriptive observations (e.g., "The water got colder," or "The edges of the tray look dry").
2. Walk around, prompting questions and encouraging group discussion:
   • Why do you think the water evaporated quickly (or slowly)?
   • What could we change to make it faster?

Step 3: Group Data Collection (10 minutes)

1. After 10 minutes of observation, gather the class together. Groups present their observations.
2. Create a class chart on the board with each group’s setting and their evaporation results (e.g., "Sunlight = Fastest").

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4. Wrap-Up: Discussion and Key Takeaways (10 minutes)

Objective: To consolidate learning and reflect on how evaporation connects to the water cycle.

1. Whisper-Pair-Share: In pairs, ask students:

   • What surprised you about today’s experiment?
   • If you could redo the experiment, what would you do differently?

2. Use their answers to guide a short teacher-led discussion about factors affecting evaporation (heat, movement, surface area).

3. Takeaway Activity: Ask students to imagine a puddle left in their school playground. What might happen to it over the next few hours on a sunny day? Could the puddle "run out of time" in heavy rain tomorrow?

4. Finish with a "quick quiz" where students write down one question they'd ask a water droplet on its evaporation journey if it could talk.

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Homework Extension

Evaporation Journal: Ask students to place a damp piece of cloth or small amount of water in a safe spot at home. Over 24 hours, they should note:

• How long it takes to dry.
• Where it dried faster (e.g., left in sunlight vs. in the shade).
• Factors they think affected its drying speed.
  Encourage them to bring their findings to the next lesson for a group discussion on evaporation in real-life settings.

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Teacher Notes

• Safety Considerations: Ensure trays or hairdryers are handled with care. Avoid hot surfaces near students and supervise closely during fan demonstrations.
• Differentiation:
  • For lower-ability students, pair them with stronger peers in group work and support with simple language.
  • For higher-ability students, challenge them with questions about how evaporation might behave in colder environments or on other planets.
• Increased Engagement: If time allows, use theatrical role-playing to "become" the sun, heating the water molecules.

This lesson not only encourages curiosity but also fosters collaboration, hands-on learning, and real-world connections to the water cycle.