Water Cycle

Question 1

Describe the water cycle.

Answer 1

1) Groundwater moves through the soil and rock
2) Rivers flow Ingo lakes and eventually, the water returns to the ocean
3) Water evaporates from oceans, lakes and rivers - water vapour
4) As air rises, it cools, so water vapour in it condenses to form clouds
5) As water droplets get too large/heavy, they fall as rain or snow

Question 2

What is evaporation?

Answer 2

When a liquid changes into a gas

Question 3

What is condensation?

Answer 3

The change of water from its gaseous form (water vapour) into liquid water

Question 4

What is precipitation?

Answer 4

Water that is falling out of the sky (eg: rain, snow, sleet, hail)

Question 5

What is a drought?

Answer 5

A lack of water

Question 6

What is desalination?

Answer 6

A process that produces fresh drinking water by separating the water from the salts in salty water

Question 7

What is distillation?

Answer 7

The process of separating a liquid from a mixture by evaporating the liquid and condensing it so it can be collected

Question 8

What does potable mean?

Answer 8

Suitable for drinking

Question 9

What is transpiration?

Answer 9

The flow of water up into a root, up the stem and out of the leaves.

Question 10

What must happen to groundwater/river water for it to become potable?

Answer 10

It has to be filtered and chemically treated

Question 11

What must happen to seawater for it to become potable?

Answer 11

It must be desalinated (remove the salt to form freshwater)

Question 12

What happens in the process of desalination?

Answer 12

• Removes salt from water
• Energy consuming process
• Produces waste product brine
• Brine must be diluted before being released into the atmosphere (good for countries like Saudia Arabia, who have a huge oil supply)

Question 13

How can a simple solar still be used to produce potable water?

Answer 13

• Low tech solution to making small volumes of water potable without electricity
  1) Dirty water placed in still
  2) Water evaporates
  3) Condenses in lower surface of cover
  4) Trickles downslope into the collecting tube
  5) Impurities are left at the bottom of the sill

Question 14

How can people ‘harvest’ clouds for potable water?

Answer 14

• Used when there is no rains fall but clouds form regularly
• Local population capture water vapour from clouds in their nets + harvest
• Good in countries like Peru + Morocco, where people are far from the ocean and cannot afford desalination plants.