A Journey through States of Water | Science Grade 6 CBSE

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The six steps of water’s journey

Water changes its state again and again. Tap each term to see what the change is called and what makes it happen.

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The three big ideas

Solid (ice): a fixed shape and size – the particles are packed tightly and cannot move about.
Liquid (water): a fixed size but no fixed shape – it takes the shape of its container and flows.
Gas (water vapour): neither fixed shape nor size – it spreads to fill all the space it can; it is invisible in the air.
Heating and cooling switch the state. Add heat: ice melts to water at 0°C, then water turns to vapour. Remove heat: vapour condenses to water, then water freezes to ice at 0°C. The water itself is the same all along – only its state changes.

Evaporation is the slow change of liquid to vapour, happening only at the surface and at any temperature – that is how a wet floor or a puddle dries without boiling.
Evaporation is faster when it is hotter, the air is drier, there is wind, and the water surface is larger (spread-out clothes dry quicker than bunched ones).
Condensation is the reverse: vapour to liquid. The water vapour already in the air turns to droplets when it meets a cold surface – dew on grass, mist on a mirror, drops outside a cold glass.

Worked example. Drops of water collect on the outside of a steel tumbler of cold lassi. Did the lassi leak through the steel?

No. The cold tumbler cools the air touching it; the water vapour in that air condenses into liquid drops on the outside. The lassi never crossed the metal.

Common mistake: thinking the drops on a cold glass seeped through from inside. They are made from water vapour in the surrounding air, condensing on the cold surface.

Evaporation: the Sun’s heat turns water from seas, rivers and lakes into vapour, which rises into the sky. Plants add vapour too, through their leaves (transpiration).
Condensation: high up the air is cold, so the vapour condenses into tiny droplets that gather as clouds.
Precipitation: the droplets join, grow heavy and fall back as rain, or as snow on the mountains.
Collection: the water flows into rivers, lakes and the ground, returning to the sea – and the cycle begins again. This endless journey is the water cycle, which keeps fresh water moving across the Earth.

Where you'll meet it

Changing states all around you

Salt from the sea

Coastal salt farmers flood shallow pans with seawater and let the sun evaporate it. The water leaves as vapour; the dissolved salt stays behind as crystals – evaporation put to work.

Staying cool

An earthen matka keeps water cool because water seeps through its walls and evaporates, carrying heat away. Sweating cools your body the same way – evaporation always draws heat with it.

Rain & rainwater harvesting

The monsoon is the water cycle on a giant scale. Because rain is just borrowed sea water returning, towns and homes catch and store it through rainwater harvesting to last through the dry months.

Check yourself

Competency quiz

Modelled on the competency-based pattern — MCQ, assertion–reason and a case study, testing whether you can use the ideas, not just recall them.

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