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A Journey through States of Water – Class 6 Science notes, important questions and MCQs

NCERT Class 6 Science, chapter 8. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Water exists as solid ice, liquid water and gaseous water vapour. Heating and cooling change one state into another, driving the water cycle.

Changes of state

Melting: ice → water (at 0 °C); freezing: water → ice.
Evaporation: water → vapour at any temperature, faster with heat, wind and large surface area.
Condensation: vapour → water (dew on a cold glass, clouds); boiling at 100 °C.

Water cycle

Sun heats water → evaporation and transpiration → condensation into clouds → precipitation (rain, snow) → water returns to rivers, seas and ground.
Water is a precious resource; save it with rainwater harvesting and fixing leaks.

Key terms

Evaporation: change of liquid into vapour at its surface
Condensation: change of vapour into liquid on cooling
Precipitation: water falling from clouds as rain, snow or hail

Formulas

Ice melts at 0 °C; water boils at 100 °C

Important questions with answers

Name the three states of water with one example each.2 marks

Solid: ice; liquid: water in a river; gas: water vapour (steam).

What is evaporation? Give two factors that speed it up.3 marks

Evaporation is the slow change of liquid water into vapour at any temperature, from the surface. It is faster with higher temperature, wind, larger surface area and lower humidity.

Explain the water cycle with the role of the sun, and describe two ways to save water at home.5 marks

The sun heats water in oceans, rivers and lakes, and plants give out water through transpiration; the vapour rises (evaporation). Higher up it cools and condenses into tiny droplets that form clouds (condensation). Droplets join and fall as rain, snow or hail (precipitation), and water flows back to rivers and oceans or seeps underground. To save water: turn off the tap while brushing; reuse water used to wash vegetables for plants (also fix leaking taps and collect rainwater).

Quick revision

Three states: ice, water, vapour.
Evaporation causes cooling.
Water cycle is driven by the Sun.

Exam tips

Wet clothes dry faster on a sunny, windy day.
Droplets outside a cold glass come from air, not from inside the glass.

Practice MCQs

Ice changing into water is
1. freezing
2. condensation
3. melting
4. evaporation
Show answer
Answer: (c) melting. Melting.
Water vapour turning into water droplets is
1. evaporation
2. boiling
3. melting
4. condensation
Show answer
Answer: (d) condensation. Condensation.
Clothes dry fastest on a
1. cold, still day
2. rainy day
3. hot, windy day
4. foggy day
Show answer
Answer: (c) hot, windy day. Heat and wind speed up evaporation.
The main source of energy for the water cycle is
1. the Moon
2. wind
3. the Sun
4. soil
Show answer
Answer: (c) the Sun. Sun.
Wet clothes dry faster on a
1. cold, still day
2. rainy day
3. hot, windy day
4. foggy morning
Show answer
Answer: (c) hot, windy day. Heat and wind increase evaporation.
Water droplets appear outside a glass of ice water because
1. water vapour in the air condenses on the cold surface
2. water leaks through glass
3. ice melts outside
4. the glass sweats
Show answer
Answer: (a) water vapour in the air condenses on the cold surface. Condensation.
Why does sweating cool our body?
1. evaporation of sweat takes heat from the skin
2. sweat is cold
3. sweat blocks the sun
4. it adds water
Show answer
Answer: (a) evaporation of sweat takes heat from the skin. Evaporative cooling.
Water droplets on the outside of a cold glass come from
1. water leaking through glass
2. the ice inside evaporating
3. melting of the glass
4. water vapour in the air condensing
Show answer
Answer: (d) water vapour in the air condensing. Condensation.

All chapters of Class 6 Science

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.