Ch.9.4

Question 1

Acid reacts with some metals (eg ___________________). During the reaction, a ________________ and ________________ are produced.

Answer 1

magnesium, salt, hydrogen

Question 2

HYDROGEN FACT FILE 👐
—Hydrogen is a ________________ gas.
—How do we test for hydrogen?

Answer 2

colourless;
we can use a burning splint to test for hydrogen. when the burning splint is placed over a test tube containing hydrogen, the hydrogen burns with a ‘pop’ sound

Question 3

When metal reacts with acid, ________________________________________________. We say that the acid ________________ the metal.

Answer 3

its size decreases slightly, corrodes

Question 4

Name the metals in the:
most reactive (1st tier)
2nd tier
3rd tier
least reactive (4th tier)
AND describe their reaction with acids.

Answer 4

1st — potassium, sodium — explosive reaction
2nd — magnesium, aluminium, zinc, iron — reacts with dilute acid, more slowly down the series
3rd — lead — very slow reaction
4th — copper, mercury, silver, gold — no reaction

Question 5

What is the word equation for the reactions between acid and metals?

Answer 5

acid + metal —> salt + hydrogen

Question 6

hydrochloric acid + magnesium —> ??

Answer 6

magnesium chloride + hydrogen

Question 7

hydrochloric acid + aluminium —> ??

Answer 7

aluminium chloride + hydrogen

Question 8

sulphuric acid + magnesium —> ??

Answer 8

magnesium sulphate + hydrogen

Question 9

sulphuric acid + aluminium —> ??

Answer 9

aluminium sulphate + hydrogen

Question 10

Besides reacting with metals, acids also react with _______________________________. Many ________________ ________________ contain this substance.

Answer 10

calcium carbonate, building materials

Question 11

Give two examples of buildings made mainly of substances containing calcium carbonate.

Answer 11

The Kowloon Masjid and Islamic Centre in Hong Kong — marble

The Great Pyramid of Giza in Egypt — limestone

Question 12

________________ and ________________ both contain calcium, which reacts with ________________ to produce a ________________, ________________ ________________ and ________________.

Answer 12

Marble, limestone, acids, salt, carbon dioxide, water

Question 13

CARBON DIOXIDE FACT FILE 👐
—Carbon dioxide is a ________________ gas
—When carbon dioxide is mixed with ________________, it ________________________________________________.

Answer 13

colourless, limewater, turns the limewater milky

Question 14

Some building structures such as ________________ ___________ and ___________________ are made of marble. We should avoid ________________________________________________________________ _______________________________________________.

Answer 14

kitchen tops, windowsills, using acidic cleaners to clean marble surfaces as acids will corrode the material

Question 15

Apart from marble and limestone, some substances such as ________________, ________________ and ________________ also contain calcium carbonate. They will be ______________________ by acids.

Answer 15

pearls, seashells, eggshells, corroded

Question 16

What is the word equation for reactions between acids and carbonates?

Answer 16

acid + carbonate —> salt + carbon dioxide + water

Question 17

hydrochloric acid + calcium carbonate —> ??

Answer 17

calcium chloride + carbon dioxide + water

Question 18

sulphuric acid + calcium carbonate —> ??

Answer 18

calcium sulphate + carbon dioxide + water

Question 19

nitric acid + calcium carbonate —>

Answer 19

calcium nitrate + carbon dioxide + water

Question 20

Rainwater is naturally ________________ ________________ and has a pH value of about ___________. If the rainwater is more acidic than it should be, it is considered to be _____________ _____________.

Answer 20

slightly acidic, 5.6, acid rain

Question 21

________________ ________________ are the main cause of acid rain. Over the past two centuries, _________________________________________________________________________________________________________________________________________. This releases a lot of ________________ ________________ including ________________ ________________ and ________________ ________________, which are ________________ gases.

Answer 21

Human activities.
more and more fossil fuels have been burned in power stations, factories and vehicles
air pollutants, sulphur dioxide, nitrogen oxide, acidic

Question 22

What are the three steps of the formation of acid rain?
1.
2.
3.

Answer 22

1. Acidic gases such as sulphur dioxide and nitrogen oxides are released into the atmosphere
2. They dissolve in water droplets and then sulphuric acid and nitric acid are produced respectively
3. These acidic droplets later join to form clouds and fall as acid rain

Question 23

What are the sources and types of acidic gases that cause the formation of acid rain?
sources:
—
—
—
types:
—
—

Answer 23

—Power stations (sulphur dioxide)
—Factories (sulphur dioxide)
—Vehicles (nitrogen oxide)
;
—sulphur dioxide
—nitrogen oxides

Question 24

Fossil fuels contain some ________________ ________________. The burning of fossil fuels causes ________________ to react with ________________ producing ________________ ________________.

Answer 24

sulphur impurities, sulphur, oxygen, sulphur dioxide

Question 25

What are the three effects of acid rain on the environment and living things? 1. 2. 3.

Answer 25

1. Corroding metal objects and building materials 2. Damaging plants 3. Causing harm to aquatic life

Question 26

Why is acid rain a problem for everyone?

Answer 26

This is because acidic gases (eg sulphur dioxide and nitrogen oxides) may be spread by wind over long distances, causing damage not only to the place where the acidic gases come from.

Question 27

Elaborate on how acid rain corrodes metal objects and building materials. — — —

Answer 27

Acid rain corrodes metal objects such as iron fences, bridges and motor car bodies It also corrodes building materials and statues made of metal or marble.

Question 28

``` Elaborate on how acid rain damages plants. — — — — — — ```

Answer 28

—Acid rain may destroy the leaves of plant directly, especially high-altitude forests. —The plants die if they cannot carry out photosynthesis (due to the lack of leaves). —Acid rain also dissolves and washes away the nutrients in the soil —As a result, the plants cannot get enough nutrients for growth; They may grow slowly or even die. —Acid rain also increases the acidity of soil —Many plants cannot grow well in acidic soil

Question 29

``` Elaborate on how acid rain causes harm to aquatic life. — — — — — ```

Answer 29

—If acid rain enters lakes and rivers, it increases the acidity of water —Most aquatic life cannot survive in water which is too acidic —Low pH levels kill fishes, their eggs and food organisms —Acid rain also dissolves minerals in the soil, washes them out of the soil and carries them into the rivers and lakes —Some of these minerals are harmful and may slow down the growth and reproduction of aquatic life

Question 30

Conclude how acid rain is formed.

Answer 30

Acid rain is formed when acidic gases like sulphur dioxide and nitrogen oxides dissolve in rainwater.

Question 31

Name one natural cause of acid rain.

Answer 31

Erupting volcanoes emit sulphur dioxide.

Question 32

Why do statues made of marble turn yellow in colour?

Answer 32

This is because acid in the air reacts with calcium carbonate of marble.