Chapter 1
Fundamentals of chemistry
Chapter Exercise
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
science, observations, experiments
substances, compositions, structures, properties, changes
Oxygen, atmosphere
chemically combined together, hydrogen, oxygen.
heating, electrolysis
mixture
chlorine, compound
element, compound, mixture
retains, different
ppearance , dour , aste , ensity , elting
chemical
physical
new
A
B
D
C
C
D
B
B
A
D
A
D
C
B
D
A
30. (a) A = beaker, B = test tube, C = Bunsen burner, D = wire gauze, E = tripod
stand, F = heat-proof mat, G = test tube holder, H = evaporating dish
(evaporating basin)
(b) (i) Test tube (B).
(ii) Test tube(B), test tube holder (G), Bunsen burner (C) , heat-proof mat
(F).
(iii) Beaker (A), tripod stand (E), wire gauze (D), Bunsen burner (C),
heat-proof mat (F).
31. (a)
(b)
(c)
(d)
(e)
Tasteless; no smell; colourless; liquid at room conditions
React with iron; react with sodium
Water changes into steam at 100oC. / Water changes into ice at 0oC.
It is because no new substance is formed.
Iron reacts with water to form iron rust. / Sodium reacts with water to form
hydrogen gas.
(f)
New substance (e.g. rust or hydrogen gas) is formed.
32. (a) Chlorine, hydrogen, iron, mercury , oxygen, sodium and sulphur
(b) An element is a pure substance that cannot be broken down into anything
simpler by chemical methods.
(c) Ammonia, sodium chloride and water
(d) A compound is a pure substance made up of two or more elements
chemically combined together
(e) A mixture consists of two or more pure substances (elements or compounds)
which have not chemically combined together.
(f) Sodium chloride solution is a mixture (because a solution is a homogeneous
mixture).
33. (a) No. Both oxygen and hydrogen are gases at room conditions while glucose
is a solid at room conditions. Carbon is black in colour while glucose is
white.
(b) Glucose solution is a mixture. It is because there is no chemical reaction
taking place between glucose and water.
(c) Glucose + oxygen  carbon dioxide + water
34. Compounds and mixtures are different in a number of ways. These include:
(1) Compounds have fixed chemical composition while mixtures have variable
chemical composition. Examples: water and air
(2) During the formation of compounds, a chemical change occurs. New
substances are always formed. On the other hand, a mixture is obtained
when different substances are physically mixed. There is no chemical
change. No new substance is formed and the change is seldom accompanied
by energy changes. Examples: formation of water from hydrogen and
oxygen, mixing of sand and sugar
(3) Properties of a compound are very different from that of its constituent
elements. For example, water is colourless liquid while hydrogen and oxygen
are colourless gases. On the other hand, each constituent substance retains
its own properties in mixtures. For example, nitrogen and oxygen are both
colourless gases no matter whether they are isolated or present together in
the air.
(4) Separation of the constituents of a compound requires a chemical process.
For example, breaking water down into the elements hydrogen and oxygen
requires a chemical process called electrolysis. On the other hand,
separation of a mixture requires a physical process only. For example,
separation of iron powder from a mixture just requires the use of a magnet.
35.  PHYSICAL PROPERTIES of a substance are those properties that can be
determined without the substance changing into another substance.
 Examples of physical properties of a substance include colour, odour (smell)
and physical state. For example water is a colourless, odourless liquid under
room conditions.
 CHEMICAL PROPERTIES of a substance are the chemical reactions of the
substance, and the respective conditions under which each reaction takes
place.
 Examples of chemical properties of a substance include how fast and
vigorous
it reacts (i.e., its reactivity) with another substance, the
condition(s) needed for it to react with other substances and what products
can be produced when
it reacts with other substances. For example,
hydrogen reacts vigorously with
oxygen (or air) only when lit with a
burning splint to form water.
Chapter 2
The atmosphere
Class Practice
A2.1
(a) People in ancient times had little scientific knowledge. In fact, any visible
portion of the Earth appeared more or less flat to the eyes.
(b) Satellite photos clearly show that the Earth is roughly spherical.
(Other answers may be given.)
A2.2
atmosphere
crust
mantle
inner core
outer core
A2.3
1. (a) No. (7 planets have an atmosphere.)
(b) Yes.
2. There is no air on the Moon.
A2.4
Elements
nitrogen
oxygen
helium
neon
argon
krypton
xenon
Compounds
carbon dioxide
water vapour
A2.5
(a)
Helium
Neon
Nitrogen
Argon
Oxygen
Krypton
Xenon
Carbon dioxide
269
246
196
186
183
153
109
78
(b) Neon and helium.
Chapter 2
The atmosphere
Chapter Exercise
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
crust, mantle , core, atmosphere
atmosphere
nitrogen, oxygen
fractional distillation
liquefied
supporter
glowing
A
A
B
B
B
D
14. (a) Nitrogen
(b) Carbon dioxide and water vapour
(c) Oxygen, argon, neon, helium, krypton, xenon (any two)
15. (a) The volumes of the three gases obtained i.e. argon, nitrogen and oxygen are
930 litres, 78,000 litres and 21,000 litres respectively.
(b) Fractional distillation
(c) No. Oxygen is the most reactive gas in air, whereas nitrogen is unreactive,
which serves the good purpose of ‘diluting’ oxygen in air. If there were
more oxygen in air, metals would be oxidized and corroded faster. Things
would also burn easier, so there would be a greater hazard of fire.
16. (a) Fractional distillation of liquid air
(b) Oxidizing
(c) Physical property: colourless, odourless
Chemical property: it supports combustion
(d) Put a glowing splint into a test tube containing the gas to be tested. If the
gas is oxygen, the splint relights.
17. (a)
(b)
(c)
(d)
Nitrogen and oxygen
Oxygen
copper + oxygen  copper(II) oxide
50 cm3  33 cm3 = 17 cm3
17 cm 3
(e)
 100% = 34%
50 cm 3
(f) 21%
(g) The percentage of oxygen in dissolved air (34 %) is much greater than that
in the atmosphere (21 %) because oxygen is more soluble in water than
nitrogen.
18.  Fractional distillation of liquid air is used to separate nitrogen and oxygen
from air.
 The air is first liquefied by repeated cooling and compression.
 Then the liquid air is warmed up bit by bit very slowly.
 Different gases in air boil at different temperatures, so they can be collected
one by one.
 The one boiling off first is nitrogen (boiling point 196 C). The second one to
be collected is argon(boiling point 186 C) /noble gas. Then oxygen gas
(boiling point 183 C) is collected.
Chapter 5
Atomic structure
Class Practice
A5.1
They are the only two liquid elements.
A5.2
1. (a) Only an element can be classified as a metal or non-metal. Water is not an
element.
(b) Non-metal.
(c) Metal.
2. (a) Mercury. All are metals. Mercury is a liquid, while the others are solids at
room conditions.
(b) Sulphur. Sulphur is a non-metal, while the others are metals.
(c) Iodine. All are non-metals. Iodine is a solid, while the others are gases at
room conditions.
(d) Graphite. All are non-metals. Graphite conducts electricity, while the others
are non-conductors of electricity.
A5.3
(a) (i)
(ii)
(iii)
(b) (i)
(ii)
(iii)
(c) (i)
(ii)
(iii)
Mg
Ag
Na
Ar,
He
Ne
fluorine
bromine
mercury
A5.4
(a) 118
(b) Br
(c) N
(d) The element copper or a copper atom.
A5.5
(a) The commonest type of hydrogen atom.
(b) 91 electrons. Number of neutrons cannot be predicted.
(c) It is not an atom. The numbers of protons and electrons are not equal.
A5.6
A magnesium atom would be changed to a chlorine atom.
A5.7
1. (a) silver
(b) silver
(c) silver
2.
(a) Aluminium
(b)
27
Al
13
(c) (i) 13
(ii) 13
(iii) 27  13 = 14
A5.8
(a) 3
(b)
16
O
8
(16O, or oxygen-16)
A5.9
(a) 37
(b) 35
(c) 4
(d) 238
(e) We cannot tell from the given data.
(The mass number is not given.)
A5.10
(a) Relative atomic mass of sodium
= mass number of the only type of sodium atom
= 23
(b) Relative atomic mass of neon
20  90  22 10
=
= 20.2
100
A5.11
(a)
(b)
(c)
(d)
A5.12
(a) 17
(b) (i)
(ii)
2,8,7
Chapter 5
Atomic structure
Chapter Exercise
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
physical
bromine, mercury
metals, non-metals
metals, non-metals, graphite
ymbol
smallest part
element
atoms
nucleus, neutrons, nucleus, electrons
positively, negatively, neutral
protons
mass number
same, different
carbon-12
weighted average, relative isotopic
shells
electronic arrangement (electronic configuration)
B
D
D
B
C
D
C
D
26. (a) True. This is because there is no gaseous metal or semi-metal at room
conditions.
(b) False. This is because mercury is a liquid metal at room conditions.
(c) False. This is because carbon (graphite) is a non-metal which can conduct
electricity. / This is because semi-metals cannot conduct electricity by
themselves.
(d) False. This is because some metals (e.g. sodium) are soft.
(e) True. This is because metals are silvery white, golden or brown in colour.
No metal is red in colour.
27. (a) The mass number of an atom is the sum of the number of protons and
neutrons in the atom.
(b) The atomic number of an atom is the number of protons in the atom.
(c) Isotopes are different atoms of the same element, with the same number of
protons (and electrons) but different numbers of neutrons.
(d)
(e)
Atom Number of Number of Electronic
protons
neutrons configuration
10 B
5
5
2, 3
5
11 B
5
6
2, 3
5
10  20  11 80
 10.8
100
28. (a) Q and R
(b) Carbon
(c) Carbon-13 and carbon-14
(d) 135 P, 136 Q, 146 R, 147 S
29. (a)
Atom
(a)
(b)
(c)
35
Cl
17O
40
Ar
Atomic
no.
Mass
no.
17
8
18
35
17
40
Number of
protons
neutrons
17
18
9
8
22
18
Electronic
electrons arrangement
17
2, 8, 7
8
2, 6
18
2, 8, 8
(b)
(c) Neon
(d) Argon is very unreactive.
30.
 Elements can be classified according to their physical states. For example, at
room temperature, hydrogen and oxygen are gases; bromine and mercury are
liquids; carbon and iodine are solids.
 Elements can also be classified into metals and non-metals. A few elements
have properties in between those of metals and non-metals. They are
classified as semi-metals.
 Examples of metals include sodium and mercury; examples of non-metals
include bromine and hydrogen; examples of semi-metals include boron and
silicon.
Chapter 6
The Periodic Table
Class Practice
A6.1
(a) Period 7, Group II; alkaline earth metals.
(b) Radium.
(c) Yes. Radium is a metal (all metals conduct electricity).
A6.2
Element X: Metal
Element Y: Non-metal
Element Z: We cannot tell from the given data as elements in Group IV can be a metal,
non-metal or semi-metal.
A6.3
(a) 2, 8, 8, 2.
(b) Yes, it is a metal.
(c) (ii).
A6.4
(a) Yes. By knowing the chemical properties of familiar elements in the same group
and the group trend, predictions about the unfamiliar element can be made.
(b) Astatine: D; strontium: A
Chapter 6
The Periodic Table
Chapter Exercise
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
electrons, outermost
ascending, atomic numbers
period, group, eight,
period number, outermost
metals, semi-metals, non-metals
chemical
1, 1, increases
7, halogens, decreases
8, noble gases
B
B
D
C
C
C
C
D
18.
Element Electronic
arrangement
A
2, 6
B
2, 8, 2
C
2, 8, 8, 1
D
2, 8
E
2, 8, 18, 3
F
2, 8, 18, 18, 7
Atomic
number
8
12
19
10
31
53
Period
number
2
3
4
2
4
5
Group
number
VI
II
I
0/VIII
III
VII
19. (a)
(b)
(c)
(d)
2
They all have two electrons in the outermost shell.
Increase down the Group.
(i) Beryllium reacts very slowly with water.
(ii) Barium reacts vigorously with water.
(e) Barium is more reactive than calcium. It should be stored under paraffin.
20. (a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
Magnesium, silicon, chlorine. They are in Period 3.
Lithium, rubidium, caesium. They are in Group I.
Iron, copper
Caesium
Fluorine
Silicon
Helium
Helium, fluorine, chlorine
Fluorine, chlorine
21. (a)
(b)
(c)
(d)
(e)
22.
Group II
Alkaline earth metals
Strontium has 2 outermost shell electrons.
Strontium is a silvery white solid at room conditions.
Strontium reacts with cold water more readily than calcium does and
colourless gas bubbles are given off. This is because the reactivity of Group
II elements will increase down the group.
 In the modern Periodic Table, elements are arranged in ascending order of
atomic number.
 The elements are arranged in periods and groups of the Periodic Table.
A horizontal row of elements is called a period while a vertical column of
elements is called group.
 Period number = number of occupied electron shells
Group number = number of electrons in outermost shell
 Elements within the same group of the Periodic Table have similar chemical
properties.
 Across a period, the elements change from metals through semi-metals to
non-metals.
 Some of the groups have special names. Group I elements are named as alkali
metals; Group II elements are named as alkaline earth metals; Group VII
elements are named as halogens; Group 0 elements are named as noble gases.
The elements in between Group II and Group III are called the transition
elements.