9G Environmental Chemistry
Level by Level
(1996 to 2006)
Commentary
Acid rain is the main event when you are planning delivery of this unit.
A lesson on global warming might not go amiss (but has not yet been tested
explicitly as far as I can tell).
A good chance to revisit 7E Acids and Alkalis, and 9I Energy and
Electricity.
This is the distribution of questions/Levels (omitting questions which fit more
naturally elsewhere :
Level
no. of
qu.s
3
4
5
6
7
0
0
1
0
3
What are the implications for your planning?
Level 5
1.
Burning fossil fuels causes air pollution.
(a) (i)
Give the names of two fossil fuels.
....................................... and ..............................................
1 mark
(ii) Some fossil fuels contain sulphur.
Complete the word equation for the reaction between sulphur
and oxygen in the air.
sulphur + oxygen → ..........................................................1 mark
(b) Burning fossil fuels leads to the formation of acid rain.
Acid rain has collected in this lake.
A helicopter is dropping calcium hydroxide into the lake.
1
Calcium hydroxide dissolves in water to form an alkaline solution.
(i)
What effect does an alkali have on the pH of an acidic lake?
..................................................................................................1 mark
(ii) When calcium hydroxide reacts with sulphuric acid in the lake a
calcium salt is formed.
What is the name of this salt?
Tick the correct box.
calcium
carbonate
calcium
chloride
calcium nitrate
calcium
sulphate
1 mark
(c) The photograph below shows trees damaged by acid rain.
(i)
The trees have lost their leaves and have died.
Explain why leaves are needed for a tree to grow.
..............................................................................1 mark
(ii)What effect does acid rain have on buildings made from
limestone?
............................................................................1 mark
maximum 6 marks
2
Level 7
2.
The chemical name for pure limestone is calcium carbonate. When
calcium carbonate is heated to a temperature above 825°C it produces
calcium oxide and carbon dioxide.
(a) Complete the symbol equation for this reaction.
CaCO3 → .............................. + ..............................
2 marks
(b) The photograph shows a limestone statue that has been changed by
acid rain.
Some gases which pollute the air dissolve in rainwater to form acids.
(i)
Give the name of a gas which dissolves in rainwater, leading to
the formation of sulphuric acid.
.......................................................................................................
......
1 mark
(ii) Complete the word equation for the reaction between calcium
carbonate and sulphuric acid.
calcium + sulphuric → ........................... + ...........................+
water
carbonate acid
2 marks
maximum 5 marks
3
3.
(a) Complete the word equation below for the reaction between calcium
carbonate and hydrochloric acid.
carbon
calcium hydrochloric
+
→ ................................... +
+ water
dioxide
carbonate
acid
1 mark
Limestone is mainly calcium carbonate. It is weathered by acids in the air
or in soil.
(b) In June 1990, a Year 9 class planned a long-term investigation into
the chemical weathering of limestone by acids in soil.
They put limestone chippings of similar size in three nylon mesh
bags.
They buried the bags outside in soils of different pH.
(i)
Chemical weathering took place in sample A, and the mass of
the sample decreased.
Give the reason for the decrease in mass. Use the word
equation above to help you.
.........................................................................................1 mark
(ii) The pupils predicted that chemical weathering would not take
place in samples B and C.
Give the reason for their prediction.
........................................................................................1 mark
(iii) Some chemical weathering did take place in samples B and C.
What could have changed the conditions in these soils to cause
weathering to take place?
........................................................................................1 mark
4
(c) The table shows how the mass of each sample changed between the
years 1990 and 2000.
year
sample A, at
pH 5
mass, in g
sample B, at
pH 7
1990
1000
1000
1000
1995
980
992
997
2000
960
984
995
sample C, at
pH 8
In 2000, a year 9 class buried another identical 1000 g sample of
limestone chippings in soil of pH 6.
(i)
Use the results in the table to predict an approximate value for
the mass of this sample in 2010.
................. g
1 mark
(ii) Why is it not possible to be certain what the mass of this sample
will be in 2010?
............................................................................................1 mark
Maximum 6 marks
4.
This table shows where different pollutants in the air come from.
source of pollutants
percentage
from power
stations
percentage
from road
traffic
percentage
from other
sources
sulphur dioxide
72
2
26
nitrogen oxides
28
51
21
smoke
6
46
48
carbon monoxide
1
90
9
pollutants
5
(a) Which two pollutants in the table above cause acid rain?
1. ..........................................................................................................
2. .........................................................................................................
2 marks
(b) Lichens are organisms which grow on buildings and trees. They
are affected by some pollutants.
Use the information in the table to suggest why few lichens
survive close to power stations but many survive alongside
roads.
................................................................................................1 mark
(c) The two products of complete combustion of petrol are not
shown in the table. Give the names of the two products of
complete combustion of a fuel such as petrol.
1. .................................................................................................
2. ................................................................................................
2 marks
(d) Smoke contains particles of carbon. These can burn when there
is enough oxygen present. Write a word equation for the
reaction of carbon with excess oxygen.
................................................................................................1 mark
(e) Which term best describes the combustion process?
Tick one box.
decomposition
oxidation
pollution
respiration
1 mark
Maximum 7 marks
6