Desalination plants remove salt from seawater to produce fresh water. Fog catchers collect water from fog to provide fresh water in arid areas. Water purifiers remove impurities from water, such as tap water, to make it safe for drinking.

1. Unit 4Unit 4
How to make fresh waterHow to make fresh water

2. How to make fresh waterHow to make fresh water
 Desalination: A desalination plant takesDesalination: A desalination plant takes
salt water from the sea and removes allsalt water from the sea and removes all
the salt from it. It produces clean freshthe salt from it. It produces clean fresh
water.water.

3. How to make fresh waterHow to make fresh water
 Fog Catchers: fog is like clouds that areFog Catchers: fog is like clouds that are
close to the ground. Fog catchers collectclose to the ground. Fog catchers collect
the water in fog. They give people freshthe water in fog. They give people fresh
water.water.

4. Fog CatchersFog Catchers
http://www.youtube.com/watch?v=7EeYlg-Q_f8

5. Water PurifierWater Purifier
 Water purifiers removeWater purifiers remove
impurities from water.impurities from water.
They will often make tapThey will often make tap
water taste better. Inwater taste better. In
Vietnam you cannot drinkVietnam you cannot drink
tap water but if you put thetap water but if you put the
water through a purifier itwater through a purifier it
is safe to drink.is safe to drink.

6. What is the difference betweenWhat is the difference between
water and ice?water and ice?
 Water can change its state when itWater can change its state when it
becomes colder (loses heat) or hotterbecomes colder (loses heat) or hotter
(gains heat)(gains heat)

7. What is the difference betweenWhat is the difference between
water and ice?water and ice?
 Freezing: when water loses heat itsFreezing: when water loses heat its
temperature drops. When water is cooledtemperature drops. When water is cooled
to below 0to below 0° C it changes to ice. When° C it changes to ice. When
water changes from a liquid to a solidwater changes from a liquid to a solid
state we say that it freezes.state we say that it freezes.
 http://www.youtube.com/watch?http://www.youtube.com/watch?
v=Qp97Ky5Tsa8v=Qp97Ky5Tsa8

8. The change in volume and weightThe change in volume and weight
during freezing and meltingduring freezing and melting
 When water freezes and turns into ice itsWhen water freezes and turns into ice its
weight stays the same but its volumeweight stays the same but its volume
increases.increases.
 Water expands when it freezes.Water expands when it freezes.
 When ice melts and turns into water itsWhen ice melts and turns into water its
weight stays the same but its volumeweight stays the same but its volume
decreases.decreases.
http://www.youtube.com/watch?v=4i5r65QGUpw

9. Circle the correct answerCircle the correct answer
 When water changes from liquid to solid it isWhen water changes from liquid to solid it is
called freezing/ melting.called freezing/ melting.
 FreezingFreezing
 When water changes from solid to liquid it isWhen water changes from solid to liquid it is
called freezing/ meltingcalled freezing/ melting
 MeltingMelting
 If we freeze 100g of water its volume willIf we freeze 100g of water its volume will
increase/ decrease.increase/ decrease.
 increaseincrease

10. The effects of Ice in natureThe effects of Ice in nature
 Water enters cracks in the groundWater enters cracks in the ground
 Water freezes and expandsWater freezes and expands
 Rocks break off and cause a landslide.Rocks break off and cause a landslide.

11.  Landslides can be caused by water in theLandslides can be caused by water in the
ground freezing and expanding. Theseground freezing and expanding. These
rocks at the top of a hill break off and asrocks at the top of a hill break off and as
they fall they break off rocks lower downthey fall they break off rocks lower down
the slope.the slope.
http://www.youtube.com/watch?v=ceym2c18OQM
http://www.youtube.com/watch?v=RDOuwMj7Xzo