Page 64 - ICSE Chemistry 6

Water is liquid at room temperature, but it changes to ice on
cooling. When water is heated, it changes to vapour (steam). condensation
Similarly, steam on cooling changes back to liquid and ice
kept at room temperature for 5–10 minutes changes to water precipitation
(liquid). However, the proper es of water remain the same in evaporation
transpiration
all the three states.
Hea ng Hea ng
Ice Water Vapour or steam

(gas) Cooling (solid) Cooling
percolation
Water cycle is another example of change of water from one
groundwater
state to another. Water cycle clearly shows that ma er can be
Fig. 3.6: Water cycle
converted from one state to another and back to its original
state without any change in its chemical composi on.

Activity 3.11

Aim: To observe change in state of ma er by making some mango/orange/lemon juice popsicles
Materials required: A bowl having juice, a popsicle stand or mould and a refrigerator

Procedure
• Take some juice (mango/orange/lemon) in a bowl, which is
liquid at room temperature.
• Now fi ll the popsicle stand or mould with the juice and place
it in the freezer compartment of the refrigerator.
juice popsicles (solid)
• Take it out a er 4–5 hours. (at room temperature) (after freezing)
Observa on: The juice turns into popsicles.
Conclusion: The temperature in the freezer is lower than the room temperature. This shows that lowering
in temperature causes the change in state of ma er, i.e., from liquid juice to solid popsicles. Also, we can
say that the change in temperature results in the change in the state of ma er.

Similarly change in pressure also brings about a change in state of ma er.

• LPG is a gas under normal condi ons but it is converted to liquid state (at high pressure) which is
present in LPG cylinders as cooking gas.
• Oxygen contained in oxygen cylinders used by pa ents in hospitals also contain oxygen in liquid
state.

Change of a Solid to a Liquid

Mel ng: We have learnt that the molecules of a solid vibrate about
their respec ve fi xed posi ons. When ice is kept at room temperature,
it gains heat energy from its surroundings. On gaining heat energy,
the molecules start moving faster. A er some me, a stage is
reached when the energy gained by the molecules overcomes the
Fig. 3.7: Melting of ice

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