F2 IS 2nd Term WS09 Answers

10.5    Acid rain

i      Words to know:

	English term	Write the words again	Chinese term
1	Acid rain		酸雨
2	Pollutant		污染物
3	Sulphur / Sulphur dioxide		硫 / 二氧化硫
4	Nitrogen oxides		氮氧化合物
5	Dissolve		溶解
6	Power station		發電廠
7	Fuels		燃料
8	Coal		煤
9	Petroleum		石油
10	Catalytic converter		催化反應器

i      Fill in the blanks:

Acid rain

l  Clean or unpolluted rainwater is slightly acidic with a pH value of about 5.6.

         When the pH value of rainwater drops below 5.6, it is regarded as acid rain.

Causes of acid rain

l  Acid rain is mainly caused by acidic pollutant gases like Sulphur dioxide

and nitrogen oxides. They are released from traditional power station, factories and motor vehicles.

l  The acidic pollutant gases dissolve in tiny water droplets in the air to form acids. The acidic

         water droplets gather together to form clouds, and finally fall as acid rain.

l  The two main sources of acidic pollutant gases are:

(a)        Traditional power stations and factories

Ø  When coals and fuels obtained from petroleum are burnt in traditional power stations and factories, sulphur dioxide and nitrogen oxides are released.

(b)       Motor vehicles

Ø  When fuels are burnt in the engines of motor vehicles, Sulphur dioxide and nitrogen oxides are released.

Environmental effects of acid rain

1           Corroding buildings and structures

l   Acids have corrosive effects on some metals and building materials.

l   Acid rain can gradually corrode building materials and structures made of metal / limestone, marble and limestone / metal.

2           Killing water life

l   Acid rain makes the water in lakes and rivers so acidic that fish and plant cannot survive.

l   Many fish and plants die if the pH value of water drops below 5.

3           Damaging plants

l   Acid rain makes soil too acidic and thus affects plant growth.

l   Acid rain also damage leaves and make plants unable to carry out photosynthesis.

Preventive measures against acid rain

l  Some major ways to reduce the emission (排放) of Sulphur dioxide and nitrogen oxides:

Ø   saving energy so that less coals and fuels obtained from petroleum are burnt;

Ø   using alternative energy sources like solar / nuclear / water power and wind power;

Ø   using high-grade fuels with a low sulphur content;

Ø   reducing pollutants from the exhaust gas of motor vehicles by using catalytic converter.

i      Concept checking:

Decide whether the following statements are true or not and try to rewrite the correct statements.

1.       Unpolluted rainwater is neutral.                                                                                                                       True / False

Unpolluted rainwater is slightly acidic

2.       Rainwater with a pH value below 7 is regarded as acid rain.                                         True / False

Rainwater with a pH value lower than 5.6 is regarded as acid rain.

3.       Carbon dioxide is the major gas that causes acid rain.                                                   True / False

Sulphur dioxide and nitrogen oxides are the major gases that cause acid rain.

4.       The main sources of pollutant gases that cause acid rain are traditional power stations,     True / False

factories and motor vehicles.                                                                                  

5.       Solar power, wind power and nuclear power are alternative energy sources which can  reduce the emission of acidic pollutant gases.                                                                                   True / False