Page 218 - New Medley 4 Semester 2 PDF (Merged)

Water kept in the plate evaporates faster. The activity shows that evaporation is

faster when the surface area is larger.
• Hands-on Learning
Activity

To check the effect of speed of wind on evaporation
Take two identical handkerchiefs and dip them in water. Squeeze the water from them. Now,
hang one of them in a room under the fan and the other one in a corner where the air of the fan
cannot reach. Observe both the handkerchiefs after 15 minutes. Which handkerchief dries first?
Can you say why?

The handkerchief hung under the fan dries first. This activity shows that the rate

of evaporation is faster for a higher speed of wind.
Have you ever thought why clothes dry faster on a hot sunny day than on a

rainy day? During rainy days, the air has more moisture (water vapour) in it.

The amount of water vapour present in air is called humidity. When humidity
is high, the rate of evaporation is low. During summers, humidity is low and
the rate of evaporation is faster. Therefore, clothes dry faster on a hot sunny day.

Condensation
The process of changing of water vapour into liquid water on cooling is called

condensation. In nature, clouds are formed by the condensation of water vapour
in the atmosphere.

Precipitation

All liquid and solid forms of water falling from the atmosphere on the Earth’s

surface is called precipitation. Rain, snow, hail, dew, fog and frost are different
forms of precipitation.

Rain

Falling of water in the form of drops is called rain.

Water evaporates continuously from water bodies
like lakes, rivers, oceans, etc. After reaching a certain

height in the atmosphere, water vapour changes into
small droplets forming clouds. These small droplets

in clouds collide with one another and form bigger
drops. When the drops become large and heavy, they Rain

fall down in the form of rain.

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