The Water Cycle

Question 1

what does energy from the sun cause water to do and what does it turn it into

Answer 1

• it causes it to evaporate

- turning it into water vapour

Question 2

what is transpiration and how does it contribute to the water cycle

Answer 2

• the evaporation of water from the leaves of plants

- the water also turns into water vapour

Question 3

why is warm water vapour carried upwards

Answer 3

because warm air rises

Question 4

what happens to warm water vapour as it rises

Answer 4

it cools and condenses to form clouds

Question 5

what is precipitation

Answer 5

• water falling from the clouds onto land

- which is usually rain but could be snow or hail

Question 6

what does the process of precipitation provide

Answer 6

fresh water for plants and animals

Question 7

what happens to the water that has been rained down unto land after it has nourished plants and animals

Answer 7

• it drains into the sea

- and the whole process starts all over again

Question 8

why is the water cycle so important

Answer 8

• if not the water cycle constantly recycling water
• we would quickly run out of it
• that would be devastating as all living organisms on earth need water in order to survive

Question 9

why is drought such a big problem

Answer 9

because we mainly rely on precipitation to get fresh water for drinking

Question 10

what is the method that we use to produce potable water in times of drought

Answer 10

desalination

Question 11

what does desalination simply do

Answer 11

it removes salts from salt water

Question 12

what is the main method of desalination that is used

Answer 12

thermal desalination
- which is where salt water is boiled in a large enclosed vessel so that the water evaporates
-

Question 13

how does thermal desalination work

Answer 13

• salt water is boiled in a large enclosed vessel so that the water evaporates
• the steam rises to the top of the vessel
• but the salts stay at the bottom
• the steam travels down a pipe from the top of the vessel
• and condenses back into pure water

Question 14

what is osmosis

Answer 14

• the net movement of water across a semi-permeable membrane

- from an area of high concentration to an area of low concentration

Question 15

why could you also say that osmosis is the movement of water from an area of low salt concentration to an area of high salt concentration

Answer 15

• because the higher the salt concentration in a solution
• the lower the water concentration
• so water would travel to the area with the high salt concentration

Question 16

what does reverse osmosis do

Answer 16

• it reverses the process of osmosis

- to get rid of impurities in water

Question 17

how does reverse osmosis worl

Answer 17

• salt water is treated to remove solids
• before being fed at a very high pressure into a vessel containing a semi-permeable membrane
• the pressure causes the water molecules to move in the opposite direction of osmosis (from a higher salt concentration to a lower salt concentration)
• as the water is forced through the membrane, the salts are left behind
• therefore removing them from the water