NCERT Questions – 5

Physical State of Water at Different Temperatures

The physical state of water (solid, liquid, or gas) depends on its temperature:

  • Below 0°C → Water is in the solid state (ice).
  • Between 0°C and 100°C → Water is in the liquid state.
  • At 100°C and above → Water starts converting into gas (steam/vapor).

What is the physical state of water at—
(a) 25o °C

 

Answer:
  • Room temperature is around 25°C.
  • Water exists in its liquid form at this temperature because it is above freezing point (0°C) but below boiling point (100°C).
  • Water molecules are loosely packed and can flow freely.

Water is in the liquid state at 25°C.

(b) o °C

 

Answer:
  • 0°C is the freezing/melting point of water.
  • At this temperature, water can exist as both solid (ice) and liquid (water).
  • If we cool water, it freezes into ice at 0°C.
  • If we heat ice, it melts into water at 0°C.

Water exists as both solid and liquid at 0°C.

(c) 100 °C ?

 

Answer:
  • 100°C is the boiling point of water.
  • At this temperature, water starts converting into steam (gas) through boiling.
  • Some water is still in liquid form, while some changes into water vapor.
  • This is called a phase transition (liquid to gas).

Water exists as both liquid and gas at 100°C.

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