A Journey through States of Water
Water is the only common substance we see as a solid, a liquid and a gas. This Class 6 Curiosity chapter follows water through its three states, the changes between them — melting, freezing, evaporation, condensation and boiling — and how these changes drive the water cycle that recycles water on Earth.
Learning objectives
- Name the three states of water.
- Describe changes of state of water.
- Explain the water cycle.
- Appreciate the importance of water.
Key concepts
Three states of water
Water exists in three states: as a solid (ice), a liquid (water) and a gas (water vapour). It is the same substance in each — only its form changes. Ice has a fixed shape, liquid water flows and takes the shape of its container, and water vapour spreads out as an invisible gas.
Changes of state
Heating and cooling change water between states. Melting turns ice to water on heating, and freezing turns water to ice on cooling. Evaporation turns water to vapour slowly from the surface, while boiling does so quickly throughout on strong heating. Condensation turns vapour back to water on cooling.
The water cycle
These changes repeat endlessly in nature as the water cycle. Heat from the Sun evaporates water from seas, rivers and lakes; the vapour rises, cools and condenses into clouds; and the water returns to the ground as rain or snow (precipitation). This cycle keeps recycling Earth's water.
Importance of water
Water is essential for life — we drink it, plants and animals need it, and it is used for cooking, cleaning, farming and many other purposes. Because fresh water is limited, the water cycle that renews it, and our careful use of it, both matter greatly.
Key definitions
- Evaporation
- The slow change of a liquid into vapour from its surface.
- Condensation
- The change of vapour back into liquid on cooling.
- Water cycle
- The continuous movement of water through evaporation, condensation and precipitation.
- Precipitation
- Water falling to the ground as rain, snow or hail.
Solved examples
Q1. Ice melting into water is a change caused by:
Solution: Heating (warming the ice).
Q2. What is the gaseous state of water called?
Solution: Water vapour.
Q3. Water droplets forming on a cold glass show which process?
Solution: Condensation.
Common mistakes to avoid
- Thinking ice, water and vapour are different substances (they are the same).
- Confusing evaporation (slow, surface) with boiling (fast, throughout).
- Mixing up condensation (vapour to liquid) with evaporation (liquid to vapour).
- Believing water is unlimited and never needs conserving.
A Journey through States of Water — MCQ Quiz
10 questions with instant feedback. Use number keys 1–4 to answer.
The solid state of water is:
Practice questions
Short answer
Name the three states of water.
Solid (ice), liquid (water) and gas (water vapour).
What is condensation?
The change of water vapour back into liquid water on cooling.
What drives the water cycle?
Heat from the Sun.
Long answer
Describe the three states of water and the changes between them.
Water occurs in three states of the same substance. As a solid it is ice, which has a fixed shape; as a liquid it is water, which flows and takes the shape of its container; and as a gas it is water vapour, which is invisible and spreads out. Heating and cooling change water between these states: melting turns ice to water and freezing turns water to ice; evaporation slowly turns surface water to vapour, while boiling does so rapidly throughout on strong heating; and condensation turns vapour back into liquid on cooling. So by adding or removing heat, water moves from one state to another.
Explain the water cycle and why it is important.
The water cycle is the continuous journey of water through its states in nature. Heat from the Sun evaporates water from seas, rivers and lakes into vapour, which rises and cools high above, condensing into tiny droplets that form clouds. When the droplets grow heavy, water falls back to the ground as rain or snow, called precipitation, and collects in water bodies and soil, ready to evaporate again. This cycle is important because it constantly recycles the Earth's limited fresh water, supplying the water that all living things, farms and homes depend on.
HOTS (Higher Order Thinking)
Why do water droplets appear on the outside of a glass holding a cold drink?
Water vapour in the surrounding air touches the cold glass, cools, and condenses into liquid droplets on the surface.
On a sunny day, a wet floor dries faster than on a cloudy day. Why?
More heat from the Sun speeds up evaporation, so the water turns to vapour and the floor dries faster.
Quick revision
Revision notes
- States of water: solid (ice), liquid (water), gas (vapour) — same substance.
- Heating: melting, evaporation, boiling; cooling: freezing, condensation.
- Water cycle: evaporation → condensation (clouds) → precipitation.
- Water is essential and limited, so it must be used carefully.
Key takeaways
- Water is the same substance in all three states.
- Heat and cooling change water's state.
- The water cycle recycles Earth's fresh water.
Frequently asked questions
What are the three states of water?
Solid (ice), liquid (water) and gas (water vapour).
What is the difference between evaporation and boiling?
Evaporation is slow and from the surface; boiling is fast and throughout the liquid.
What is the water cycle?
The continuous movement of water through evaporation, condensation and precipitation.