Transcript Cell Questions

Hydrosphere
p. 298-301
Hydrosphere
 Formed
by all bodies of water on the
Earth’s surface
 Includes oceans, rivers, streams, lakes
and other waterways
Hydrosphere
 Covers
75% of Earth’s surface
 Without water there would be no life
 Water can either be fresh or salty
Why are the seas and Oceans
salty?
 Seas
and Oceans are salty because there
are a great quantity of mineral salts
dissolved in it
 Mineral salts come from rocks
 When it rains, some minerals (which form
the rocks) dissolve
 Minerals run into the ocean where they
accumulate
Are some Seas saltier than others?
 The
amount of salt in seas vary depending
on the region in the world
The Dead Sea –
Saltwater Lake in
the Middle East
with salinity of 27%
Which type of water can
humans drink?
 Humans
can only drink fresh water
because they can’t absorb the large
quantity of mineral salts contained in salt
water
 When water is safe
to drink it is called potable.
 Potable water = drinkable water
Potable Water
 To
be potable water it must have the
following characteristics:
 Perfectly transparent
 No suspended particles
 No unpleasant odour
 Contains little dissolved minerals
 Contains dissolved oxygen
 No micro-organisms that cause disease
Potable Water
 5.6
billion people in the world
 1.1 billion people in the world without
access to adequate water and sanitation
 Water is whose responsibility?
But how much water is available
for humans to drink?
Works out to be about
0.02% available fresh
water
The Water Cycle
The Water Cycle



a) Evaporation - water from lakes, rivers and
oceans changes to water vapour by the action of the
sun.
b) Transpiration - water vapour is released from
plants by the action of the sun.
c) Condensation - water vapour changes to
droplets of liquid as it cools, leading to the formation
of clouds.


d) Precipitation - water from clouds is released
back into lakes, rivers and oceans, as rain, snow or
hail, or onto land where it seeps through the soil and
travels as ground water back to the ocean.
e) Melting - ice and snow change to liquid water by
the addition of heat, and flow into lakes, rivers and
oceans.
People upset the natural
water cycle
 That
is because we:
 Create pollution
 Remove the natural vegetation such as
plants and trees
 Pave over the natural environment and
build houses etc.
 Put in irrigation systems, build dams,
change natural drainage systems, build
wells