F2 IS 2nd Term WS10 Answers

11.1    Senses and sense organs

i      Words to know:

	English term	Write the words again	Chinese term
1	Sense		感覺
2	Detect		探測
3	Stimuli		刺激
4	Respond		反應
5	Sense organ		感覺器官
6	Receptor		感受器
7	Sensitive		敏感
8	Brain		腦
9	Nerve		神經
10	Interpreted		詮釋

i      Fill in the blanks:

1       We have different senses such as sight, hearing, smell, taste and touch.

2       Changes in the environment are called stimuli. Living things can detect and respond to them.

3       By responding to stimuli, living things can find food, mates, shelters and escape from danger.

4       We have different sense organs like eye, ear, tongue, nose and skin. They contain special kinds of cells called receptors which are sensitive to particular kinds of stimuli.

5       When the receptors detect stimuli, they send signals to our brain through nerves, which are then interpreted to give us senses.

i      Fill in the table:

Sense organ	Stimuli	Senses produced
Eye	Light	Sight
Ear	Sounds	Hearing
Nose	Chemicals in air	Smell
Tongue	Chemicals in food or drinks	Taste
Skin	Things in contact with the skin	Heat/cold, touch, pain, pressure

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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

                                                                                  

F2 IS 2nd Term WS08 Answers

10.4    Acids and corrosion

i      Words to know:

	English term	Write the words again	Chinese term
1	Corrode (vb)		腐蝕 (動詞)
2	Corrosion (n)		腐蝕 (名詞)
3	Corrosive (adj)		腐蝕性的
4	‘Pop’ sound		爆鳴聲
5	Hydrogen		氫
6	Marble		大理石
7	Limestone		石灰石
8	Calcium carbonate		碳酸鈣

i      Fill in the blanks:

1             Some metals (e.g. zinc and magnesium) react with dilute acids. During the reactions, hydrogen

gas and heat are produced. The metals decrease in size gradually. Thus acids have corrosive

effects on these metals.

2           To test for hydrogen, a burning splint is put near the mouth of the test tube containing the gas. It burns

with a ‘pop’ sound if the gas is hydrogen.

3             We should not use acidic detergents to clean marble / limestone and limestone / marble

surfaces because both of them contain calcium carbonate, which are easily

corroded by acids. The reaction gives out carbon dioxide.