F2 Worksheet 10.5 answers

10.2            Acid rain

I.    Words to know:

	English term	Write the words again	Chinese term
1	Acid rain	Acid rain	酸雨
2	Sulphur dioxide	Sulphur dioxide	二氧化硫
3	Nitrogen oxides	Nitrogen oxides	氮氧化物
4	Dissolve	Dissolve	溶解
5	Power station	Power station	發電廠
6	Sulphur	Sulphur	硫
7	Catalytic converter	Catalytic converter	催化反應器

II.   Fill in the blanks:

1.     Acid rain

Ø   Clean or unpolluted rainwater is slightly acidic and has a pH value of about 5.6.

Ø   When the pH value of rainwater drops below 5.6, it is regarded as (1) acid rain.

2.     Causes of acid rain

Ä  Acid rain is mainly caused by the acidic pollutant gases like (2) sulphur dioxide and (3) nitrogen oxides. A large amount of these pollutant gases are released from traditional power stations, factories and motor vehicles.

Ä  The acidic pollutant gases (4) dissolve in tiny water droplets in the air to form acids. The acidic water droplets in the air gather together to form clouds, and finally fall as acid rain.

(a)   Traditional power stations and factories

²  When coal and fuels obtained from petroleum are burnt in traditional (5) power station and factories, sulphur dioxide and nitrogen oxides are released.

(b)   Motor vehicles

²  When fuels are burnt in the engines of motor vehicles, sulphur dioxide and nitrogen oxides are released.

2.     Environmental effects of acid rain

(a)   Corroding buildings and structures

²  Acids have (6) corrosive effects on some metals and building materials.

²  Acid rain can gradually corrode buildings and structures made of metals, marble and limestone.

(b)   Killing water life

²  Acid rain makes the water in lakes and rivers so acidic that fish and plants cannot survive.

²  Many fish and plants (7) die if the pH value of water drops below 5.

(c)   Damaging plants

²  Acid rain makes soil too acidic and thus affects plant growth.

²  Acid rain may also damage leaves and make plants unable to carry out (8)

                photosynthesis.

3.     Preventive measures against acid rain

Ø   Some major ways of reducing the emission of sulphur dioxide and nitrogen oxides:

²  saving energy so that less coal and fuels obtained from petroleum are burnt;

²  using alternative energy sources like (9) solar / nuclear and wind power;

²  using high-grade fuels with a low (10) sulphur content;

²  reducing pollutants from the exhaust gas of motor vehicles, e.g. using (11) catalytic converter;

²  educating the public about the harmful effects of acid rain and the ways of reducing air pollution.