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5.1 This question is about acid rain.

a) Choose words to complete the sentences.

Rain has always been a weak . acid alkali carbon dioxide nitric oxygen sulphuric sulphur dioxide This is because rain dissolves some of the . acid alkali carbon dioxide nitric oxygen sulphuric sulphur dioxide that is in the air.  Over the last 200 years, rain has become more strongly acidic. When coal and oil are burnt in power stations the poisonous gas . acid alkali carbon dioxide nitric oxygen sulphuric sulphur dioxide is released into the air.  When this gas dissolves in rain it produces . acid alkali carbon dioxide nitric oxygen sulphuric sulphur dioxide acid.

b) Acid rain causes rivers and lakes to become acidic. Many fish cannot survive in such water so they die. To reduce the acidity in lakes, large quantities of limestone (calcium carbonate) are often added to the water.

i) Why should the addition of limestone reduce the acidity of the water in a lake?

ii) The reaction would take place quicker if the limestone was first powdered. Why?

iii) What gas is produced when limestone reacts with an acid? 

5.2 a) The action of a number of weathering agents, such as the Sun and plants, breaks down large rocks.

Complete the table by describing how each agent breaks down rock.

b) Look at the drawings of two gravestones. Both gravestones are over 80 years old and made from limestone

Gravestone A is in a graveyard in the middle of a busy city, gravestone B is in a graveyard many kilometres from the nearest town.

   Explain why gravestone A is more weathered than gravestone B.

5.3 An increase in the amount of carbon dioxide in the air is thought to increase the average temperature of the Earth’s atmosphere. This effect is called global warming.

a) Which two effects increase the amount of carbon dioxide in the air? Tick the correct boxes.

b) Some scientists think that global warming will cause the flooding of any low-lying land in coastal areas. How could global warming cause this to happen?

c) Look at the information in the table:

i) How has the amount of carbon dioxide in the air changed in the last 160 000 years?

ii) What has happened to the average temperature over the last 160 000 years?

iii) What trend links the amount of carbon dioxide in the air and the average temperature?