TEACHGYAN • CLASS 6 SCIENCE • CURIOSITY
Chapter 8 – A Journey through States of Water
States of water • Melting • Freezing • Evaporation • Condensation • Water cycle • Activities • MCQs • Worksheet
Chapter focus: Water can exist as solid ice, liquid water and water vapour. Heating and cooling cause changes of state, and these changes are continuously involved in the water cycle.
🎯 Learning Goals
- Identify the three states of water.
- Describe melting, freezing, evaporation and condensation.
- Explain factors that affect evaporation.
- Understand water vapour and its role in the atmosphere.
- Trace the basic water cycle.
- Use observations to explain changes of state.
💧 1. Three States of Water
| State | Example | General features |
|---|---|---|
| Solid | Ice | Has a definite shape and volume. |
| Liquid | Water | Has definite volume but takes the shape of its container. |
| Gas | Water vapour | Has neither definite shape nor definite volume. |
🔥 2. Melting and Freezing
Melting is the change of a solid into a liquid on heating. Ice melts into water. Freezing is the change of a liquid into a solid on cooling. Water freezes into ice.
☀️ 3. Evaporation
Evaporation is the change of liquid water into water vapour from the surface of a liquid. It can occur below the boiling point. Evaporation becomes faster when the exposed surface area is larger, the surrounding air is moving faster, or the temperature is higher.
❄️ 4. Condensation
Condensation is the change of water vapour into liquid water on cooling. Tiny droplets can form when moist air meets a cooler surface.
☁️ 5. Water Vapour Around Us
Water vapour is present in the air even though it is invisible. When moist air cools sufficiently, water vapour can condense into tiny droplets, contributing to clouds, fog or dew.
🌧️ 6. Water Cycle
- Sunlight provides energy for evaporation from water bodies and moist surfaces.
- Water vapour rises and cools.
- Condensation forms tiny droplets and clouds.
- Water returns to Earth as precipitation such as rain.
- Water collects in rivers, lakes, oceans and soil and the cycle continues.
🧪 7. Explore and Observe
- Place an ice cube in a cup and observe it as it warms.
- Put a small amount of water in a shallow dish and observe it over time.
- Compare evaporation from two similar dishes, keeping one in moving air.
- Observe droplets forming on the outside of a cold glass and discuss condensation.
Safety: Never handle boiling water or hot equipment without adult/teacher supervision.
📋 Worked Examples
Example 1 – Wet Clothes
Wet clothes dry because liquid water at their surface evaporates into the air. Warmth, airflow and greater exposed surface can speed the process.
Example 2 – Cold Glass
Water droplets on the outside of a cold glass come from water vapour in the surrounding air that has condensed; they do not normally come through the glass.
Example 3 – Ice and Water
Ice and liquid water are different states of the same substance. Heating can change ice into water, while cooling can change water back into ice.
🧠 Think Like a Scientist
- Why does water in a shallow plate generally evaporate faster than water in a narrow container?
- Why does moving air help wet clothes dry faster?
- How is evaporation different from boiling?
- Where does the water on the outside of a cold glass come from?
- Why is the water cycle important for life on Earth?
📝 Important Practice Questions
- Name the three states of water.
- What is melting?
- What is freezing?
- Define evaporation.
- Define condensation.
- Name three factors that can affect the rate of evaporation.
- What is water vapour?
- Explain the water cycle briefly.
- Why do wet clothes dry faster on a windy day?
- Why do droplets form on a cold glass?
🔥 Competency / HOTS
- Design a fair activity to compare evaporation from two surfaces.
- Explain why a fan can make wet clothes dry faster without heating them strongly.
- A student says that clouds are made of invisible water vapour only. Explain what happens during condensation.
- Trace one water molecule’s possible journey from an ocean to a cloud and back to land.
- Explain how melting and freezing are opposite changes of state.
🧩 MCQ Practice
- Ice is water in the — A. solid state B. liquid state C. gaseous state D. plasma state
- Change of ice into water is — A. melting B. freezing C. condensation D. filtration
- Change of water into water vapour from a surface is — A. evaporation B. freezing C. melting D. sedimentation
- Water vapour changing to liquid water is — A. condensation B. evaporation C. melting D. boiling
- Which generally increases evaporation? A. greater surface area B. still air only C. lower temperature D. covering the surface completely
- Water vapour in air is generally — A. invisible B. blue solid C. always visible D. ice
- Cloud formation involves — A. condensation B. handpicking C. sieving D. melting only
- The water cycle is driven largely by energy from the — A. Sun B. Moon only C. soil only D. rocks
Answer Key: 1-A, 2-A, 3-A, 4-A, 5-A, 6-A, 7-A, 8-A
📄 Printable Worksheet
- Draw and label the three states of water.
- Differentiate melting and freezing.
- Explain evaporation and list three factors affecting it.
- Explain condensation with an everyday example.
- Why does a cold glass develop droplets outside?
- Draw the water cycle and label its major processes.
- Describe one activity demonstrating evaporation.
- Explain why water is continuously changing state in nature.
- Write five daily-life examples involving changes of state.
- List two safety precautions while studying hot water.
🔁 Quick Revision
| Concept | Remember |
|---|---|
| Solid | Ice; definite shape and volume. |
| Liquid | Water; definite volume, variable shape. |
| Gas | Water vapour; no definite shape or volume. |
| Melting | Solid → liquid. |
| Evaporation | Liquid → vapour from the surface. |
| Condensation | Vapour → liquid. |
| Freezing | Liquid → solid. |
✅ Mastery Checklist
- ☐ I can identify the three states of water.
- ☐ I can explain changes of state.
- ☐ I can explain evaporation and its factors.
- ☐ I can explain condensation.
- ☐ I can trace the water cycle.
- ☐ I can design simple observations safely.