Science · Class 6 · Chapter 8

A Journey through States of Water

• Evaporation — Liquid water turning into vapour.
• Condensation — Water vapour turning into liquid.
• Melting — Solid turning into liquid.
• Freezing — Liquid turning into solid.
• Humidity — The amount of water vapour in the air.
• Water vapour — The invisible gas form of water.
• Water cycle — The continuous movement of water between Earth and the sky.

Chapter 8 · Concept 1 of 8

Ice and Water — Two States, One Substance

• Leave an ice cube in a cup, and it turns into water. Ice and water are two forms — states — of the same substance.
• Ice (solid) — Keeps its own fixed shape. Can be held, does not flow or spread.
• Water (liquid) — Takes the shape of its container. Flows and spreads, but keeps the same volume.

Chapter 8 · Concept 2 of 8

Evaporation

• A puddle on the playground disappears by evening. A wet floor dries up. Where does the water go?
• Evaporation — The process of conversion of water into its vapour state. It happens continuously, even at room temperature — the water turns into invisible water vapour, it doesn't just seep away.

Chapter 8 · Concept 3 of 8

Condensation

• Fill a glass with cold water and ice — soon, droplets appear on the outside. They aren't seeping through the glass; they're forming from water vapour in the air.
• Condensation — The process of conversion of water vapour into its liquid state. Dew on morning grass, and droplets under a pot's lid, form the same way.

Chapter 8 · Concept 4 of 8

Properties of Ice, Water, and Vapour

• | Shape | Flows? | Spreads to fill space?
• Ice (solid) — Fixed — No — No
• Water (liquid) — Takes shape of container — Yes — No — keeps its volume
• Water vapour (gas) — None — Yes — Yes — fills all available space

Chapter 8 · Concept 5 of 8

Melting, Freezing, Evaporating, Condensing

• Ice (Solid) → Water (Liquid) → Water vapour (Gas)

Chapter 8 · Concept 6 of 8

Faster or Slower Evaporation

• More surface area — Water spread on a plate evaporates faster than the same water in a bottle cap.
• Higher temperature — Water in sunlight evaporates faster than water kept in shade.
• More wind — Clothes dry faster on a windy day than on a still day.
• Higher humidity slows it — Clothes dry slower on a rainy, humid day — the air already holds more water vapour.

Chapter 8 · Concept 7 of 8

The Cooling Effect of Evaporation

• The matka effect — Water seeps through the porous walls of an earthen pot (matka) and evaporates, cooling the water inside — steel pots don't do this.
• Everyday examples — Sweating and fanning cool our body as sweat evaporates. Sprinkling water on floors or roofs in summer cools the surroundings the same way.

Chapter 8 · Concept 8 of 8

Clouds, Rain, and the Water Cycle

• Evaporation from oceans & rivers
• Water vapour rises and cools
• Condenses into clouds
• Falls as rain, hail, or snow

Quick Recap

Check Your Understanding

1. 1Which best describes condensation? (i) Water converting to vapour (ii) Liquid changing to gaseous state (iii) Clouds forming from droplets (iv) Water vapour converting into its liquid state
2. 2In which is evaporation very important — (i) colouring with crayons, water colours, acrylic colours, or pencil colours? (ii) writing with pencil, ink pen, or ball point pen?
3. 3The space around natural grass feels cooler than the space around green plastic grass. Why?