Page 147 - Science Class 06
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converted into water and water can be
converted into ice.
Let’s see how these three states of water 1. What are the three physical states of
water?
interchange:
2. What is mel ng point?
Ice can be converted into water : At a
3. Why do ny water droplets occur on the
certain temperature, ice melts into liquid.
outer surface of glass in which ice-cubes
The temperature at which a solid melts is are kept?
called the mel ng point of the solid.
EVAPORATION
Evapora on is the process by which water
changes from a liquid to a gas or vapour.
Water boils at 212°F (100°C), but it actually
begins to evaporate at 32°F (0°C); it just
occurs extremely slowly. As the temperature
Water turns into water vapour on hea ng.
increases, the rate of evapora on also
Water can be converted into water vapour: increases.
At a certain temperature, a liquid starts The amount of evapora on depends on the
conver ng into vapour. Water boils at 100°C temperature and it also depends on the
and starts conver ng into water vapour. The
amount of water that is to be evaporated.
temperature at which a liquid boils is called
For example, there is not much evapora on
boiling point of that liquid.
occurring in the Sahara Desert, but why?
Water vapour can be converted into water: Although it can get extremely hot in the
When water vapour is cooled, it turns into Sahara, it’s just sand, there’s just not much
liquid. This process is called condensa on. water to be evaporated.
You will study about the condensa on later
There are certain factors that influence the
in this chapter.
process of evapora on. The water present
in the water bodies con nuously evaporates
due to heat during the day. But, the rate of
evapora on may be affected by these
factors.
v When it is a windy day, the rate of
Water can be converted into ice : Some evapora on becomes faster.
liquid turns into solid on cooling. The v At high temperature, evapora on
temperature at which a liquid turns into becomes faster.
solid is called the freezing point of that v Hot and dry air also increases the rate of
liquid. Water turns into solid (ice) when it is evapora on.
cooled below 0°C.
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