Investigating Factors Affecting Evaporation
Absolutely, Mayank! Here's a student-friendly, activity-based explanation of "Activity 1.14 – Factors Affecting Evaporation", fully aligned with CBSE Class 9 Science, and designed to make the concept practical and memorable for your students.
🌬️ Activity 1.14 – Investigating Factors Affecting Evaporation
🎯 Objective:
To understand how surface area, temperature, humidity, and wind speed affect the rate of evaporation.
🧪 Materials Required:
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3 containers:
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Test tube (narrow opening)
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Open china dish
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15 mL of water (5 mL per container)
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Clock or calendar
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Notebook to record observations
📝 Steps to Perform:
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Pour 5 mL of water into each container:
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Test tube – keep near a window or fan
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China dish – keep near the same window/fan
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Another china dish – keep inside a cupboard or classroom shelf
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Record:
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Room temperature
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Time taken for water to fully evaporate in each case
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Repeat the experiment on a rainy/humid day and compare the results.
📊 What to Observe:
| Condition | Surface Area | Air Flow | Humidity | Expected Result |
|---|---|---|---|---|
| Test tube near window | Low | High (fan/window) | Moderate | Slow evaporation |
| China dish near window | High | High | Moderate | Fastest evaporation |
| China dish in cupboard | High | Low | Moderate | Slower than near window |
| Same setups on rainy day | Same | Same | High | All evaporation rates will be slower |
🧠 Inferences from the Activity:
✅ 1. Surface Area Matters
Larger surface area → faster evaporation
🔍 Water in the china dish evaporates faster than in the test tube.
✅ 2. Temperature Affects Evaporation
Higher temperature → faster particle motion → quicker evaporation
🔍 On a sunny day, water evaporates faster than on a rainy day.
✅ 3. Wind Speed Helps
Higher wind speed = vapour is carried away quickly
🔍 Water near the fan or open window evaporates faster than inside a cupboard.
✅ 4. Humidity Slows Down Evaporation
More moisture in air → less room for new vapour
🔍 On humid days, drying takes much longer.
📘 Conclusion:
The rate of evaporation increases with:
| ✅ Factor | 🔍 Reason |
|---|---|
| Increased surface area | More particles exposed to air |
| Increased temperature | More particles get kinetic energy to escape |
| Lower humidity | Air can accept more vapour |
| Higher wind speed | Vapour is carried away, allowing more to escape |
💬 Ask Your Students:
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Why did the water evaporate faster in the china dish than in the test tube?
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What happened when you repeated the experiment on a rainy day?
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Why do we spread clothes to dry them faster?
🎤 Closing Line for Class:
“Evaporation is nature’s quiet but clever trick — it speeds up when it’s sunny, breezy, and dry, and slows down when it’s humid and still. And now, you’ve seen it for yourself!”
Would you like this made into a worksheet, lab report template, or interactive classroom activity card?
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