Page 224 - Big Ideas Year 10 sciPAD 2025

PHOTOCOPYING PROHIBITED
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224 SCIPAD - BIG IDEAS - BOOK 2
EARTH SYSTEMS
The Hydrosphere
Earth is sometimes called the ‘Blue Planet’ because 71% of its surface is water. The world’s oceans
make up 97% of the hydrosphere. The remaining 3% is fresh water.
Only about 1% of the fresh water in the hydrosphere is found as surface water (in rivers, lakes and
swamps, etc) while around 29% is ground water, beneath the Earth’s surface. The remaining 70 %
is frozen as ice and snow.
1. Using coloured pencils and the information above, complete the pie charts showing the
composition of the hydrosphere.
Land
Water Fresh water
Salt water
Surface water
Ground water
Ice and snow
The Water Cycle
The water cycle is the cycle water molecules go through on Earth. It involves evaporation, cloud
formation, precipitation and the flow of liquid water on the Earth’s surface and oceans. Most of
our weather involves processes related to the water cycle.
The hydrosphere, like the atmosphere, is always in motion. The movement of oceans, rivers and
streams can be seen easily, however the movement of water into and out of the atmosphere is
less obvious.
Heat from the Sun causes water to evaporate into the atmosphere. This water may be lying in a
puddle, in an ocean or even in the soil. Water also enters the atmosphere from plants in the form
of transpiration. Water vapour is invisible and can be carried about by the wind from place to
place. As it rises into the atmosphere it cools. This cooling action causes the water to condense to
form clouds. With further cooling the water falls from the sky as rain, snow, sleet or hail and is called
precipitation. The water that falls as precipitation moves across the surface of the Earth (called
run-off) and will flow into rivers and streams, and may eventually reach the ocean. Some of the
water seeps into the ground (a process called percolation) and becomes groundwater. Water
that falls on the surface of the Earth may then be evaporated again, continuing the water cycle.
1. Define the following terms:
(a) Evaporation: 

(b) Transpiration: 

(c) Condensing: 

(d) Precipitation: 

(e) Percolation: