Skip to content
Know.itKnow.it
Create an animated lesson
On request

Read the answer free. Creating a lesson uses your daily or stored credits; review the language and settings before starting.

What are the three states of water, and how does water change from one to another?

Class 6 ScienceNCERT chapter: A Journey through States of Waterइसे हिंदी में पढ़ें

Exam-ready answer

Water exists in three states: solid (ice), liquid (water) and gas (water vapour). Heating ice makes it melt into water, and heating water makes it evaporate into water vapour. Cooling reverses these changes: water vapour condenses into liquid water, and water freezes into ice. Only the state changes; the substance remains water throughout.

Explanation

Ice is the solid state of water. It has a fixed shape and a fixed volume. Liquid water has a fixed volume but takes the shape of its container. Water vapour is a gas: it has neither a fixed shape nor a fixed volume and spreads to fill the space available. Water vapour is invisible, which is why it is present in air without being seen.

Keep ice cubes in a glass and they slowly turn into water as they take in heat from the surroundings. This change from solid to liquid is called melting, and pure ice melts at 0 °C. When water is cooled in a freezer, it changes back into ice; this change from liquid to solid is called freezing.

Wet clothes dry in the sun because water changes into water vapour and mixes with the air. This change from liquid to gas is called evaporation; it happens at any temperature, from the surface, and becomes faster with more heat, wind and spread-out surface. When water vapour cools, for example on a cold glass, it changes back into tiny water drops. This change from gas to liquid is called condensation.

Points to remember

  1. Three states of water: solid (ice), liquid (water) and gas (water vapour).
  2. Melting: solid to liquid on heating; pure ice melts at 0 °C.
  3. Freezing: liquid to solid on cooling.
  4. Evaporation: liquid to gas at any temperature, from the surface of the water.
  5. Condensation: water vapour (gas) to liquid water on cooling.

Exam tip

Draw a triangle-style flow diagram with ice, water and water vapour at the corners and arrows labelled melting, freezing, evaporation and condensation. Mention 'heating' or 'cooling' on each arrow.

Questions students also ask

What factors make evaporation faster?
Evaporation becomes faster when the temperature is higher, when wind blows over the water, and when the water is spread over a larger surface area. That is why clothes dry quickly on a sunny, windy day when they are spread out, not folded.
Is evaporation the same as boiling?
No. Evaporation takes place slowly from the surface of water at any temperature. Boiling takes place throughout the liquid at a fixed temperature, which is 100 °C for pure water at sea level, and bubbles of vapour form inside the liquid.
How do the changes of state of water help in the water cycle?
Heat from the Sun evaporates water from oceans, rivers and lakes. The water vapour rises, cools and condenses into tiny drops that form clouds. When drops grow heavy, they fall as rain or, in cold places, as snow, and water returns to the Earth.

Chapter labels help you find the topic in your textbook. Check your own edition: chapter names and order can change. These are Know.it explanations, not official NCERT solutions.