BGCSE SCIENCE
DOUBLE AWARD
REVISION
BOOKLET
KEFENTSE MOGOPODI
CONTACTS: 74549960/
74339844
SPECIAL CONTRIBUTIONS BY
TEBO GEORGE: BACHELOR OF EDUCATION (PHYSICS)
RAYMOND MOTLHAGODI : BACHELOR OF EDUCATION (CHEMISTRY)
BITSANG ISSA BITSANG: BACHELOR OF EDUCATION (BIOLOGY)
1 Fig 1.1 shows a car of mass 500kg moving from rest with constant
acceleration of 10m/s2 . Two forces act on it, a forward force and a friction
force.
(a)(i) Calculate the resultant force acting on the car. Show your working
F = ma
F= 500kg × 10m/s2
F = 5000N
(ii) If the friction force is 2000N, calculate the forward force acting on the car.
Show your working
5000N – 2000N
Forward force = 3000N
(b)After some time, the car reaches a velocity of 20m/s . How long did it take
for the car to reach this velocity? Show your working
Solution: a = 10m/s2
𝒗−𝒖
𝒂
, v = 20m/s , u = 0m/s
=𝒕
𝟐𝟎𝒎 𝟎𝒎
−
𝒔
𝒔
𝟏𝟎𝒎/𝒔𝟐
= 2 seconds
2 Fig 2.1 shows an electrician replacing a broken bulb on a lamp post. The
lamp post is 20m high
(a)The bulb slips through the electrician’s hand and falls to the ground. The
mass of the bulb is 20g. The gravitational force on a mass of 1kg is 10N.
Calculate the kinetic energy of the bulb just before it hits the ground
Height = 20m
Mass = 20g
Force = 10N
Convert 20g mass to kilograms, m = 0.02kg
E = mgh
E = 0.02kg × 10N × 20m
E = 4J
b) what assumption did you make in your answer for (a)?
Ans: The gain in Kinetic Energy is equal to the loss in Potential Energy
3 Fig 3.1 shows the temperature – time graph of a solid substance when
heated
State what happens at each stage
Stage I :
Stage II:
Stage III:
4 (a) Fig 4.1 shows two lenses
(a)Write down the names of the lenses
Lens V : Convex lens
Lens W: Concave lens
5 Fig 5.1 shows a transformer
(a) Name the type of transformer
Ans: Step down transformer
(b)The transformer is connected to a 240V a.c power supply. The bulb requires
12V to operate normally. There are 100 turns in a secondary coil.
Calculate the number of turns in a primary coil
𝒐𝒖𝒕𝒑𝒖𝒕 𝒗𝒐𝒍𝒕𝒂𝒈𝒆
𝒊𝒏𝒑𝒖𝒕 𝒗𝒐𝒍𝒕𝒂𝒈𝒆
𝒗𝟐
𝒗𝟏
=
𝒕𝒖𝒓𝒏𝒔 𝒐𝒏 𝒕𝒉𝒆 𝒐𝒖𝒕𝒑𝒖𝒕 𝒄𝒐𝒊𝒍
𝒕𝒖𝒓𝒏𝒔 𝒐𝒏 𝒕𝒉𝒆 𝒊𝒏𝒑𝒖𝒕 𝒄𝒐𝒊𝒍
𝒏
= 𝒏𝟐
𝟏
𝟏𝟐𝑽
=
𝟐𝟒𝟎𝑽
𝟏𝟎𝟎
𝒏𝟏
𝒏𝟏 = 2000 turns
6 Fig 6.1 shows a set up used to perform an experiment on
electromagnetic effects. When the North pole of a magnet is pushed into
the coil, the galvanometer deflects to the right and back to zero.
(a) State what will happen if
(i)
The magnet is now pulled out of the coil
Ans: the galvanometer deflects to the left and back to zero
(ii)the South pole of the magnet is pushed into the coil
Ans: the galvanometer deflects to the right and back to zero
NB: refer to Lenz’s law of magnetic induction
(b)Write down three ways of increasing the size of induction
•
Increasing the number of turns in the solenoid per unit length
•
Increasing the strength of magnet
•
Move the magnet into or out the solenoid
•
Insert soft iron core into the solenoid
7 A solution of copper(II) Sulphate is electrolyzed using two copper
electrodes.
(a)Draw a diagram to show how the experiment is set up
(b)What happens during the electrolysis
(i) at the anode
Ans: Copper removed; electrode becomes thinner
(ii)at the cathode
Ans: copper deposited to the electrode, grows thicker
(iii)to the solution
Ans: the blue colour of Copper(II) Sulphate solution does not fade because
the copper ions deposited at the cathode is equal to the copper ions
dissolved at the anode
(c)Give two practical uses of this method of electrolysis.
1. Electroplating – process of coating a metal with another metal for
purpose of decoration or prevention of corrosion
2. Copper purification – electrolysis of copper transfers copper atoms from
an impure copper anode to a pure copper cathode, leaving impurities
behind
(d)What would happen if the copper electrodes are replaced with platinum
electrodes
(i)at the anode
Ans: oxygen bubbles are given off/ observation of bubbling at the anode
(ii)at the cathode
Ans: deposit of copper metal on the electrode surface
(iii)to the solution
Ans: blue colour of copper(II) Sulphate solution fades as Cu2+ are
discharged
8 The major source of the world’s energy supply is fossil fuels. The chemical
energy stored in these fuels is converted to other forms of energy such as
heat and electrical energy. There has been a considerable increase in demand
for electrical energy in the last 50 years, and other energy sources for
generating electrical energy are now being investigated urgently
(a) (i) What is a fossil fuel?
Ans: a natural fuel formed in the geological past from the remains of living
organisms
(ii)Name two fossil fuels in use at present
1. Coal
2. Oil
3. Natural gas
(b) (i) Name two elements that are found in high proportions in fossil fuels
1. Carbon
2. Hydrogen
(ii)Write an equation for the complete combustion of each elements in (b)(i)
•
•
C(s) + O2 (g)
2H2(g) + O2(g)
CO2(g)
2H2O(g)
(iii)Name another element found in fossil fuels that leads to formation of
acidic rain
Ans: Sulphur
c)Give one reason why urgent efforts are being made to find other sources
of energy as an alternative to fossil fuels
Ans: Gases produced when burning fossil fuels destroy the ozone layer
d) State one source of energy, other than direct solar energy, which may be
used as an alternative to fossil fuels
Ans: Hydroelectric power
9 After fertilization and implantation in a mammal, the placenta and the
umbilical cord develop.
(i)What is the advantage of having a dense network of blood capillaries in the
placenta?
Ans: To allow the exchange of food substances and waste products between
the baby and the mother
(ii)State the function of the umbilical cord
Ans: connects the foetus to the placenta
(b)Describe a permanent method that can be used by a woman to prevent
pregnancy
Sterilization – a woman’s fallopian tubes are tied to prevent sperms from
reaching the egg
(c)Explain why this method cannot prevent HIV infection
Ans: There is still exchange of bodily fluids that transmits the virus when
engaged in the sexual act
(d)Give one way by which HIV/AIDS can be transmitted other than by sexual
contact.
Ans: through touching open wounds of an infected person
10 Fig 11.1 shows part of the human skin
(a) Identify the parts labelled R and S
R : Hair
S : Capillary
(b)Describe how S and T help in temperature regulation in hot conditions
S : Dilates so that blood flows closer to the surface and lose much heat in
the process
T – when the temperature is too high, sweat glands take up water from
capillaries around it. Water collects in the gland, travels up the sweat duct
and comes out of skin surface. When sweat evapourates it takes heat from
the body, so it cools it down
(c)Explain why the cooling effect of T will not be felt in hot humid weather
Ans: The sweat glands are not active when the loss and gain of heat are
balanced.
11 Fig 12.1 shows the apparatus used to investigate the effect of a certain
factor on the rate of transpiration
(a)Name the factor being investigated
Ans: Humidity
(b)Define transpiration
Ans: The main force which draws water from the soil and through the plant
(c)Explain how the plastic cover affects the movement of water in the capillary
tube
Ans: As the twig transpires water is lost through leaves and trapped by the
plastic, so the area around leaves become humid with time and after some
time the transpiration rate slows down because of the humid plastic cover,
so movement of water up the capillary tube slows down too.
12 Fig 13.1 shows the urinary system of a human
(a)Name the structures A, B, E and F
A – Left kidney
B – Ureter
E – Aorta
F – Renal vein
(b)What is the function of the structure C ?
Ans : stores/ holds urine ( structure C is the bladder)
(c)How does the function of structure D in women differ from that in a man
Ans: In women. Structure D only expels urine but in men it expels urine
and semen
(d) Suggest the medical assistance given to a person who has structure A
failure
Ans: Use of kidney dialysis machine
13 Many human activities produce waste materials
Using examples of named materials, suggest environmental reasons why these
materials should be recycled.
Ans: Plastics- they are non – biodegradable so they mess up the
environment and animals dies from eating them
Papers – papers are made from wood and as such plants would get
depleted if we don’t recycle papers.
Tins – they are also non – biodegradable and mess up the environment
14 Fig 1.1 below shows a man of mass 60kg climbing up a tree to a height of
6m to escape a lion.
(a)What form of energy does he gain as he goes up the tree?
Ans: Gravitational potential energy
(b) Calculate the work done by the man in climbing up the tree( take g = 10N/
kg )
Ans: work done = Force × distance
60kg = 600N
600N × 6m
= 3600Nm
(c)I he reaches the top of the tree in 10s, what power does he develop?
Ans : Power =
Power =
𝒘𝒐𝒓𝒌 𝒅𝒐𝒏𝒆
𝒕𝒊𝒎𝒆 𝒕𝒂𝒌𝒆𝒏
𝟑𝟔𝟎𝟎𝑵𝒎
𝟏𝟎𝒔
Power = 360 watts
15 Tshepho and Kago stand in front of a high vertical cliff 640m away to
measure the speed of sound in air. When Tshepho hits a drum Kagiso starts a
stopwatch. She stops the watch when he hears the echo. The time measured
by Kago is 4s .
(a)Calculate the speed of sound in air
Ans: speed =
Speed =
𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆
𝒕𝒊𝒎𝒆
𝟔𝟒𝟎𝒎
𝟒𝒔
= 160m/s
b)How will the pitch of the original sound compare with that of the echo?
Ans: the pitch of original sound is higher than that of the echo
(c)Echo is a reflected sound so by vibrating against a medium before it bounces
back makes the waves weaker
16 Fig 3.1 shows two rays of light reflected from a pebble at the bottom of the
pool .
(a)On the diagram ;
(i)continue the paths of the two rays when they emerge from the water surface
(ii)Use the refracted rays to show the position of the image of the pebble; label
the image I
(b)The real depth of the pool is 1.5m and the image appears to be 1.1m beneath
the water surface.
Calculate the refractive index of water
Refractive index =
Refractive index =
𝒓𝒆𝒂𝒍 𝒅𝒆𝒑𝒕𝒉
𝒂𝒑𝒑𝒂𝒓𝒆𝒏𝒕 𝒅𝒆𝒑𝒕𝒉
𝟏.𝟓𝒎
𝟏.𝟏𝒎
= 1.36
17 Fig 4.1 shows the direction in which a compass needle points when it is
placed on a wooden table
Two plotting compasses are then placed near a metal bar, AB and the compass
needles point as shown in Fig 4.2
(a) How do the plotting compasses show that bar AB is a magnet?
Ans: the compass points are deflected
(b) Draw the magnetic field around AB
(c)Describe an electrical method of demagnetizing a magnet
Ans: Applying alternating current to the magnet. This destroys the
magnetic field, hence destroying the magnet.
18 (a)Fig 6.1 shows an electric heater
(a)Name the three wires
Name
Colour
1. Live
2. Neutral
3. Earth
brown
blue
yellow/ green
(b)Which two wires are connected to the heating element of the heater?
Ans: Live and neutral
(c)What is the function of the third wire?
Ans: To absorb excess electricity passing through the appliance(heater)
and to prevent overloading of the live wire.
(d)The heater is rated 250V, 1000W
(i)Calculate the normal operating current of the heater
Current =
Current =
𝒑𝒐𝒘𝒆𝒓
𝒗𝒐𝒍𝒕𝒂𝒈𝒆
𝟏𝟎𝟎𝟎𝑾
𝟐𝟓𝟎𝑽
= 4A
(ii)
From the list of fuses below, choose by a tick the lowest fuse rating
suitable to be used to protect the heater
1A , 2A , 10A , 15A
Ans: Fuse rating =
𝒘𝒂𝒕𝒕𝒔
𝒗𝒐𝒍𝒕𝒂𝒈𝒆
× 1.25
= 4A × 1.25 = 6
So, we opt for 10A
19 (a)Use a dot and cross diagrams to draw electronic structures of
(a)Methane
(ii)Calcium Chloride
(b)Give two properties of ionic compounds
1. They form crystals
2. Have high melting and boiling points
3. High enthalpies of fusion and vaporization than molecular compounds
4. Hard and brittle
5. Conduct electricity when dissolved in water
NB: CHOOSE ONLY 2
20 The equation shows the reaction between hydrogen and nitrogen to produce
ammonia.
N2 + H2 ⇋ NH3
ΔH = - 93 kj
(a)Balance the chemical equation
N2 + 3H2 ⇋ 2NH3
(b)The reaction is exothermic. Explain what this means in terms of bond
breaking and bond formation.
Ans: Reaction produces/ releases heat. Energy is released when new bonds
form and energy is absorbed.
(c)(i) What volume of nitrogen is needed to react completely with 24dm3 of
hydrogen at room temperature and pressure? ( 1 mole of a gas occupies 24dm3
at r.t.p)
1: 3
x : 24
𝟑𝒙
𝟑
=
𝟐𝟒
𝟑
x = 8dm3
(ii)Calculate the volume of ammonia produced, assuming 10% conversion
1 : 2
8 :x
x = 16dm3
(d)Give one use of ammonia
Ans: used in cleaning detergents
21 Coal is a mixture of carbon , hydrocarbons and sulphur compounds. When
coal is burned sulphur dioxide is produced
(a)Name other two gaseous products formed when coal is burned
1. Carbon monoxide
2. Carbon dioxide
(b)In a coal fired factory, sulphur dioxide can be removed before the waste
gases are released into the atmosphere.
Suggest a reason for removing sulphur dioxide
Ans: It leads to acid rain
Sulphur dioxide is removed by passing the waste gases through a mixture of
water and powdered calcium carbonate.
Explain the action in this process of
(ii)Water – to form sulphurous acid
(iii)Calcium carbonate – to convert it to carbonate sulphite ions
22 Hydrochloric acid is a strong acid and ethanoic acid is a weak acid
(a)What is meant by a strong acid?
Ans: an acid that is completely dissociated or ionized in an aqueous
solution
(b)What is the pH of dilute hydrochloric acid and of ethanoic acid likely to be
(i) dilute Hydrochloric acid : 2
(ii)dilute ethanoic acid : 4
23 Mpho likes serobe (tripe) and he eats it quite often. Dineo advises him to
exercise every day.
(a)(i) State one problem Mpho is likely to face if he eats too much serobe
Ans: increased risk of heart disease
(ii)Explain how the problem in (i) above occurs
Ans: Hardening of arteries – occurs when fat / cholesterols and other
substances build up in the walls of arteries. Over time, these deposits
completely block arteries and cause problems throughout the body as blood
circulation would be disturbed.
(b)Explain how Dineo’s advice is sensible
Ans: Exercising uses much energy and as such cholesterol from the body is
converted or broken down to avoid build up in the arteries.
(c)Dineo also suggests that Mpho should eat his serobe with plenty of fresh
vegetables.
Give one reason why this is a good advice
Ans: Fresh vegetables are low in fat and calories and are rich in potassium
to help maintain healthy blood pressure.
24 Fig 13.1 shows a setup used by two students investigating the loss of water
from a plant. They used a freshly cut shoot
(a)Name the process under investigation
Ans: Transpiration
(b)State the purpose of using oil in the experiment
Ans: To prevent water from being lost directly from the beaker
(c)(i) State the day with the highest amount of water loss
Ans: Day 6
ii)Suggest the likely weather conditions of the day
•
•
•
High temperature
Less humidity
Windy
(d)Explain the importance of nitrogen and magnesium to plants
Nitrogen: major component of chlorophyll so it helps in photosynthesis.
Magnesium : Use by plants for metabolism of carbohydrates and in cell
membrane stabilization
25 Fig 14.1 shows a section through the human skin
(a) Identify structures A and B
A : Hair
B : Blood capillary
(b)What causes shivering ?
Ans: a drop in temperature. When the core body temperature drops, the
shivering reflex is triggered to maintain homeostasis. Skeletal muscles
begin to shake in small movements, creating warmth by expending energy.
(c)(i) When the body is overheated the arterioles in the skin dilate. Explain how
this helps the body maintain a constant temperature
Ans: By dilating, blood flows closer to the surface therefore helping the
body lose heat faster and in the process maintaining a constant body
temperature
ii)Suggest how structure C is involved in maintaining a constant body
temperature during hot weather
Ans: during hot weather, sweat glands take up water from the capillaries
around it. Water collects in the gland, travels up sweat duct and comes
onto skin surface. When sweat evapourates it takes heat from the body, so
it cools it down.
26 Fig 15.1 shows parts of a flower
(a)State how this flower is pollinated
Ans: Wind pollination
(b) Describe the path taken by the pollen grain nucleus from the stigma to the
region where fertilization takes place
Ans: pollen grains absorbs liquid from the stigma and a microscopic pollen
tube grows out of the grain. This tube grows down the style and into the
ovary where it enters a small hole, micropyle in an ovule. The nucleus of
the pollen grain travels down the pollen tube and enters the ovule
27 A girl pours hot water into a bottle and a Thermos flask, Fig 1.1. She notices
that the bottle gets hotter than the flask
(a) By what process does the heat from the water in the bottle reach her hand?
Ans: Conduction
(b)State two features of Thermos flask that reduce heat loss from the flask, and
explain how each reduces heat loss
1. An insulated stopper to reduce conduction and convection
2. A double walled container with a gap between the walls. Air has been
removed from the gap to reduce conduction and convection
3. Walls with silvery surface to reduce thermal radiation
28 An electric motor rated at 200W is used to raise a 20kg bag to the roof of a
building 10m high.
(a)What form of energy does the bag gain as it rises?
Ans: Gravitational potential energy
(b)Calculate the work done to raise the bag to the roof. 1kg has a weight of 10N
.
Work done = Force × distance
= 200N × 10m
= 2000Nm or 2000 joules
(c)Assuming no energy losses, how long would it take for the bag to reach the
roof?
Power =
200W =
𝟐𝟎𝟎𝒙
𝟐𝟎𝟎
=
𝒘𝒐𝒓𝒌 𝒅𝒐𝒏𝒆
𝒕𝒊𝒎𝒆 𝒕𝒂𝒌𝒆𝒏
𝟐𝟎𝟎𝟎𝑵𝒎
𝒙
𝟐𝟎𝟎𝟎𝑵𝒎
𝟐𝟎𝟎
x = 10s
29 (a) Fig 3.1 shows the positions of air particles when two sound waves , A
and B pass through the air in the same time interval
(i)
What type of wave is a sound wave?
Ans: Longitudinal wave
(ii)Which sound wave has a higher pitch?
Ans: wave A
Explanation: Its frequency is higher than that of wave B
(iii)One wave is reflected by a vertical wall. What effect will this have on its
pitch?
Ans: the pitch lowers
Explain your answer
Ans: the waves lose energy and as such the pitch lowers
(b) A student stands 400m away from a vertical wall. She fires a starter pistol
and hears an echo after 2.4s. Calculate the speed of sound in the air.
Speed of =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑
𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
=
2 ×𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 𝑤𝑎𝑙𝑙
𝑒𝑐ℎ𝑜 𝑡𝑖𝑚𝑒
sound
2 ×400𝑚
2.4𝑠
= 333.33 m/s
30 Fig 4.1 shows two skydivers A and B falling in the air
(a) Name two vertical forces acting on each diver
• Force of gravity
• Air resistance
(b)Explain why diver B would fall faster than diver A
Ans: Diver B experiences less resistance because he doesn’t use a parachute
while Diver B does use the parachute
31 Fig 5.1 shows two resistors in parallel. These resistors can be replaced by a
single resistor X, without changing the brightness of the lamp
(a)What would be the resistance of resistor X ?
Ans: Rparallel =
𝟏
𝑹𝑻
𝟏
𝑹𝑻
=
=
𝟏
𝟖
+
𝟏
𝑹𝑻
=
𝟏
𝑹𝟏
+
𝟏
𝑹𝟐
𝟏
𝟐
𝟓
𝟖
𝑹𝑻 = 1.6 Ω
(b)What effect would removing the 8Ω resistor have on the brightness of the
lamp?
Ans: Increase in brightness of the lamp
Explanation: The resistance of the current would be reduced therefore
more current flows to the bulbs.
(c)(i)State one difference between a step-down transformer and a step-up
transformer
Ans: Number of turns on the secondary and primary coils
(ii)A Transformer connected to a 240V supply draws a current of 10A. The
voltage output of the transformer is 600V. Calculate the current in the
secondary coil
Input voltage × Input current = Output voltage × output current
240V × 10A = 600V × A2
Current in secondary coil = 4A
(iii)Why is it preferable to use low current in the transmission of electricity over
long distances
Ans: The primary reason that power is transmitted at high voltages is to
increase efficiency. The lower current that accompanies high voltage
transmission reduces resistance in the conductors as electricity flows along
the cables. This means that thin, light-weight wires can be used in longdistance transmission
32 Fig 6.1 shows the arrangement of particles in structures X and Y.
(a)(i) Write the chemical formula of a compound with structure X
Ans: NaCl
(ii)Write the chemical formula for the compound with structure Y
Ans: H2O
(b)Complete the table by naming the type of structure and bonding in X and Y
Type of structure
Bonding
X
Ionic structure
Ionic bonding
Y
Molecular bond
Covalent bonding
(c)Why does the compound with structure X have a high melting point, while
that with structure Y has a low melting point
X : due to strong electrostatic forces of attraction holding the crystal lattice
together
Y : weak intermolecular forces of attraction which exists between
molecules
(d)Give one other property each for the compounds with the bonding in X and
Y.
X : Usually conduct electricity when molten or in aqueous state
Y : Generally, do not conduct electricity when molten or dissolved in water
33 The equation represents the complete combustion of 2.0g of propane at room
temperature and pressure.
C3H8 (g) + O2 (g)
CO2 (g) + H2O(l)
(a) Balance the equation
Ans: C3H8 (g) + 5O2 (g)
3CO2 (g) + 4H2O(l)
(b)Calculate the number of moles of propane that were burnt
Number of moles =
𝒎𝒂𝒔𝒔
𝒎𝒐𝒍𝒂𝒓 𝒎𝒂𝒔𝒔
Molar mass of propane = C : 12 × 3
H: 8 × 1
= 44g/mol
No .of moles =
𝟐.𝟎𝒈
𝟒𝟒𝒈/𝒎𝒐𝒍
= 0.045 moles
c)Calculate the mass of oxygen that reacted with propane
use ratio to find moles of oxygen first
1:5
0.045 : x
= 0.227 moles
Then mass = number of moles × Molar Mass
= 0.227 × 32g/mol
= 7.27g
(d)Calculate the volume of carbon dioxide produced.
1 : 3
0.045 : x
x = 0.135 moles of CO2
So, volume , Number of gas moles =
𝒗𝒐𝒍𝒖𝒎𝒆
𝟐𝟒𝒅𝒎𝟑
Volume = number of moles × 24dm3
= 3.24dm3
(e)When the carbon dioxide produced was dissolved in water, it formed a weak
acid.
(i)What is a weak acid?
Ans: acid that produces a few hydrogen ions when it dissolves in water
ii)Name the weak acid formed
Ans: Carbonic acid
34 The worldwide chemical industry has some advantages and disadvantages if
it is not undertaken properly.
(a)State two environmental problems that may be caused by the chemical
industry
1. water pollution – kills water inhabiting organisms
2. air pollution – smokes from the industries pollute the air we breathe
(b)Some products of the chemical industry are recycled
(i)What is recycling?
Ans: processing material which is no longer in use to make other useful
products
(ii)Give two advantages of recycling
1. Helps keep the environment clean
2. Helps conserve other existing natural resources
(iii)Name one substance that can be recycled
Ans: paper
35 Dudu prepared some alcohol by mixing yeast, malt, sugar and warm
water. The mixture was left for 2 – 3 days
(a)Name the substance added to speed up the reaction
Ans: malt(act as catalyst)
(b) Name the process used to prepare alcohol
Ans: Fermentation
(c)Write an equation to represent the reaction that took place
Malt
C6H12O6 + H2O +yeast
2C2H5OH + 2CO2
(d)The equation shows the reaction between alcohol and ethanoic acid and to
form P and water
(i)
Name the group of organic compounds to which P belong
Ans: Esters
(ii)
Draw the molecular formula of P
Ans: C4H8O2
(iii)State one physical property of P
Ans: Strong and pleasant smell
36. Fig 11.1 shows blood vessels in the skin
When a person carries out vigorous exercise, there is a change in the capillary in
the skin
(a)(i) On Fig 11.1, show how the capillary would change if vigorous exercise is
carried out
(ii)Explain how the change you have shown helps in regulating body
temperature
Ans: As the capillaries dilate and blood flows close to the skin, heat can
easily be lost from the body hence helping regulate temperature.
(b)Describe the role of the following skin structures in cooling the body
(i)Hair : The hair lies flat when we are warm to help heat escape from the
body
(ii)Sweat glands : When the body temperature rises, sweat glands secrete
sweat to the surface. This sweat carries heat with it.
(iii)Receptors : detect temperature, if the skin detects increased heat, this
will lead to sweating
37. A student used three culture solutions A, B and C to investigate the
necessity of mineral salts for plant growth. Three leafy shoots were put in the
culture solutions treated as follows:
A solution with all mineral salts
B solution lacking nitrate ions
C solution lacking magnesium ions
The leafy shoots were exposed to the same conditions of growth for four weeks.
Air was bubbled through the solutions.
(a)Which plant will show the healthiest growth
Ans: Plant A
(b)Describe and explain the appearance of
(i) plant B
Appearance: leaves turn a pale green or yellow colour. This reduces
the plant's ability to photosynthesize and grow properly, which reduces the
farmers' crop yield .
Explanation: Without nitrates, the amount of chlorophyll in leaves reduces.
(ii)plant C
Appearance: stunted growth
Explanation: plant doesn’t photosynthesize so it doesn’t make any food to
help it grow
c)What was the purpose of plant A
Ans: used as a control
d)Name the process by which plants take up mineral salts
Ans: Active transport
(ii)State two ways in which the process in (i) differs from Osmosis
Ans: *Active transport requires energy to happen while osmosis doesn’t
*Osmosis is the movement of water molecules while Active transport is the
movement of soluble solutes
38. Fig 13.1 shows the percentage of undigested food taken in through the
mouth until it leaves the alimentary canal
(a)Name section B
Ans : stomach
(b)Why does the digestion of carbohydrates stop in section C?
Ans: due to absence of amylase (starch digesting enzyme)
(c)In which section does most digestion occur
Ans: section C (duodenum)
(d)State the function of section F
Ans: stores faeces before being expelled
(e)State what happens to the undigested material at G
Ans: Faeces are expelled from the body here
39. Fig 1.1 shows the speed – time graph of a ball thrown vertically
upwards (g = 10m/s2 )
(i)What is the speed of the ball at the highest point?
Ans: 0m/s
(ii)Calculate the maximum height reached
g=
𝟐𝒉
𝒕𝟐
make h the subject of the formula
h=
h=
𝒈𝒕𝟐
h = 45m
𝟐
𝟏𝟎 ×(𝟑)𝟐
𝟐
(iii)How long does the ball take to reach the highest point
Ans: 3 seconds
(iv)What is the energy transfer taking place as the ball falls from the maximum
height back to the thrower
Ans: From Gravitational Potential Energy to kinetic energy
(b)A box is pushed by a force of 100N along a surface at a constant speed of
0.5m/s in 3s.
(i)What is the friction force?
Ans: 100N ( If an object is moving at a constant speed the force of friction
must equal the applied force)
(ii)Calculate the work done in moving the box along the surface
Ans: calculate distance first
Distance = speed × time
= 0.5m/s × 3s
= 1.5 m
Work done = Force × distance travelled
= 100N × 1.5m
= 150Nm
40. Fig 2.1 shows a glass beaker containing water at 2°C
After some time, droplets of water are formed on the outside of the beaker.
Explain how the water droplets are formed on the outer wall.
Ans: It is due to condensation. The temperature of the beaker is cold enough
to cool down the water vapour in the surrounding air, so it turns from
gaseous to liquid state.
41. Fig 4.1 shows a practical application of echo sounding in mineral
prospecting( the average speed of sound in rocks is 4500m/s)
(a) A transmitter sends out shock waves and the receiver detects an echo from
the coal deposit 2 seconds later. How deep is the coal deposit in km?
Speed =
𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆
𝒕𝒊𝒎𝒆
4500m/s =
=
𝟐×𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒕𝒐 𝒕𝒉𝒆 𝒄𝒐𝒂𝒍
𝒆𝒄𝒉𝒐 𝒕𝒊𝒎𝒆
𝟐 ×𝒅
𝟐𝒔
d = 2250m
d = 2.25km
42. Fig 5.1 shows two houses which have lightning conductors. In House A,
the rod is attached to the roof while in house B the rod is attached to a
metal plate buried underground.
(a) Name a suitable metal which could be used to make the rod
Ans: Copper
(b)Explain why the house A is more likely to be damaged by lightning
Ans: the spike rod is connected directly to the roof so if struck by lightning
the house will be affected too
(c)In a storm the spikes have a positive charge as shown. Indicate on the
diagram the sign and the location of the charge on the cloud above the
spikes
43. Fig 6.1 shows an electric circuit
The reading of A3 is 1.5 A
ADDITIONAL NOTES:
Resistance in parallel =
𝟏
𝑹𝑻
𝟏
𝟏
𝟐
𝟐
= + =1
𝑹𝑻 = 1 𝜴
So, the total resistance of the circuit will be 1Ω + 3Ω = 4Ω
Total current in the circuit =
𝒗𝒐𝒍𝒕𝒂𝒈𝒆
𝒓𝒆𝒔𝒊𝒔𝒕𝒂𝒏𝒄𝒆
=
𝟏𝟐𝑽
𝟒𝜴
= 3A
State the current through
R2 = 1.5A
R1 = 3A
NOTE: In a series circuit, the sum of the voltages consumed by each individual
resistance is equal to the source voltage. ... In a series circuit, the current that
flows through each of the components is the same, and the voltage across the
circuit is the sum of the individual voltage drops across each component. We
combined R2 and R3 so that the circuit becomes series circuit
R2 and R3 are in parallel, and for components in parallel, the current is
divided amongst them that is why R2 is equal to R3 because they have to add
up to 3A
(b)Calculate the voltage across each resistor
(i) Voltage across R1
V= IR
V = 3A × 3Ω = 9V
(ii)Voltage across R2
V = 1.5A × 2Ω
V = 3V
(d)Voltage across R3
V = 1.5 A × 2Ω
= 3V
44. To improve the crop yields farmers add fertilizers like ammonium nitrate to
their fields
(a)(i)Write the chemical formula for ammonium nitrate
Ans: NH4NO3
(ii)Calculate the percentage by mass of nitrogen in ammonium nitrate
(N= 14 , H= 1 , O = 16 )
N = 14 × 2 = 28
H = 1× 4 = 4
O = 16 × 3 = 48
Total Molar mass of Ammonium Nitrate= 80g/mol
𝟐𝟖
𝟖𝟎
× 100% = 35%
(b) Lime , calcium oxide (CaO) is sometimes used to neutralize acidic soils
(i)Write an equation for the reaction between lime and dilute hydrochloric acid
CaO + 2HCl
CaCl2 + H2O
(ii)Write an ionic equation for the reaction in b(i)
Ans: O-2 (aq) +2H+ (aq)
(iii)
H2O(l)
Explain why ammonium nitrate is regarded as a good fertilizer while lime
is not
(c)Lime is obtained from the thermal decomposition of limestone, CaCO3 .
The equation shows the decomposition of 5g of limestone.
CaCO3(s)
CO2(g) + CaO(s)
(i)What is meant by thermal decomposition?
Ans: breakdown of substances using heat
(ii)State one use of calcium carbonate other than the production of lime
Ans: used as an antacid to relieve heartburn
(iii)Calculate the number of moles of calcium carbonate decomposed
𝒎𝒂𝒔𝒔
Number of moles:
𝒎𝒐𝒍𝒂𝒓 𝒎𝒂𝒔𝒔
Ca = 40
C = 12
=
𝟓𝒈
𝟏𝟎𝟎𝒈/𝒎𝒐𝒍
O = 16 × 3
= 0.05 moles
(iv)How many moles of calcium oxide would be produced?
Moles :
1:1
0.05 : x
= 0.05 moles
(v)Calculate the volume of carbon dioxide produced at room temperature and
pressure. (1 mole of a gas occupies 24dm3 at room temperature and pressure)
Ratio is 1: 1
So number of moles of CO2 is also 0.05
Therefore volume = number of moles × 24dm3
= 0.05 × 24dm3
= 12dm3
45. Study the flow chart shown
(i)What must be added to glucose to enable fermentation to take place
Ans: Yeast
(ii)State two conditions necessary for fermentation to occur
1. Sugars dissolved in water and mixed with yeast
2. Warm temperature
3. Expulsion of carbon dioxide
(b)Write the names of substances R, S and gas Q.
R : Polyethene
S : Ethane
Q: Carbon dioxide
(c)The equation shows the reaction between ethanol and ethanoic acid
C2H5OH + CH3COOH
CH3COOCH2CH3 + H2O
(i)Name the organic product for this reaction
Ans: Ethyl ethanoate
(ii)Draw the structural formula of the organic product of the reaction
46. The diagram shows the position of iron, Fe, in the periodic table
(a)Name the group of metals to which iron belongs
Ans: Transition metals
(b)State two properties of metals in the group named in (a) above
1. High melting point/ boiling point
2. Form coloured ions and compounds
(c)Iron is used in the manufacture of ammonia, NH3
(i)Draw a dot and cross diagram to show the bonding in a molecule of ammonia
(ii)What type of bonding is present in a molecule of ammonia?
Ans: Covalent bonding
(d)Ammonia dissolves in water to form a weak alkali, aqueous ammonia
(i)Why is aqueous ammonia a weak alkali?
Ans: Ammonia produces OH- ions in its water solution
(ii)Suggest the pH of aqueous ammonia
Ans: between 11 and 12
(iii)Describe how aqueous ammonia is used to test for presence of aluminium
ions in a solution
Ans: To a sample of a solution, add few drops of ammonia solution. If
aluminium ions are present, a white precipitate is formed.
47.Define a hormone
Ans: A chemical substance that is made by a specialist cell usually within
an endocrine gland and is released into the bloodstream to send a message
to another part of the body.
(b)Complete table 11.1 to show hormones, their sources and their functions
Hormone
source
Function in the body
Insulin
Pancreas
(ii)Helps control blood
glucose level by
signaling the liver and
muscles and fat cells to
take in glucose from
the blood
Adrenaline
Adrenal glands
Prepares the body for
action
48. Neo made dough using yeast. She took two equal masses of dough and
placed them in two identical dishes at different temperatures as shown in Fig
12.1 A
(a)(i) Using information in Fig 12.1 describe any changes that had taken place
in each batch of dough in dishes X and Y after one hour
X: dough has risen
Y : dough remains the same
(ii)Explain the difference in the results for the two batches of dough
Ans: In dough X, the enzymes reacted, and fermentation took place thus
leading to production of carbon dioxide which made the dough rise. In
dough Y the enzymes were destroyed by the high temperature and as such
no reaction took place in the ingredients used.
(b)Suggest why it is convenient to use microorganisms in biotechnology
Ans: Microorganisms break down and convert nutrients that have been
taken up into new products.
49. Fig 14.1 shows a diagram of a kidney machine
(a)(i)Name the process by which waste products move from the blood to the
dialysis fluid.
Ans: diffusion
(ii)State the property of the dialysis tube that makes it suitable for use in the
kidney machine
Ans: it is selectively permeable
(b)Explain how glucose is prevented from leaving the blood
Ans: The glucose level of the dialysis fluid is equal to that of the blood so
there is no net movement of glucose during dialysis
50. State two disadvantages of asexual reproduction
1. Low genetic variability
2. Adaptation to environment is difficult
(b)Complete Table 15.1 by filling in two named methods of asexual
reproduction and examples of plants where they can be applied
Table 15. 1
Method
Example
Vegetative propagation
potatoes
Budding
Maple
51. (a) Define acceleration
Ans: The rate of change of velocity per unit time
(ii)A bus stops to pick up a passenger. Its speed decreases from 22m/s to 0m/s
in 10s. Calculate its deceleration
Note: deceleration is negative acceleration
𝟎𝒎𝒍𝒔−𝟐𝟐𝒎/𝒔
𝟏𝟎𝒔
= – 2. 2m/s2
(b)Fig 1.1 shows a distance – time graph for a car journey from A to C
(i)In which region of the graph is the speed of the car constant?
Ans: A – B
(ii)For how long is the car at rest?
Ans: 200s – 125s = 75s
(c)A ball is dropped from the roof of the building. It reaches the ground in 3s. (g
= 10m/s2 ). Calculate
(i)the height of the building
Use formula
𝟐𝒉
𝒕𝟐
, make h the subject of formula
𝒈𝒕𝟐
h=
h=
g=
𝟐
(𝟏𝟎 ×𝟑𝟐 )
𝒉=
𝟐
𝟗𝟎
𝟐
= 45m
(ii)the speed of the ball as it touches the ground
Ans: speed =
𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆
𝒕𝒊𝒎𝒆
Speed =
𝟒𝟓𝒎
𝟑𝒔
= 15m/s
52. (a)Fig 2.1 shows waves on a surface of a liquid
(i)What type of wave is illustrated?
Ans: Transverse wave
(ii) On the diagram, show one wavelength and label it 𝜆
(iii) X is a particle on the surface of the liquid. On the diagram ,
draw an arrow to show the direction in which the particle is
moving
(b)Table 2.2 shows critical angles of water, diamond and glass
(i)What is a critical angle?
Ans: the angle of incidence beyond which rays of light passing through a
denser medium to the surface of a less dense medium are no longer
refracted but totally reflected.
(ii)X and Y are materials in Table 2.2. Use the information from the table and
the paths of rays in Fig 2.3 to identify materials X and Y
X:
Y:
53. Fig 3.1 shows two magnets
(a)On the diagram below draw the magnetic field around XY
Note: like pole repel each other so x is a south pole and y is a north pole
(b)Fig 3.2 shows an electromagnet next to four cubes A, Aluminium , B lead, C
nickel and D cobalt
(i)Which two cubes will the magnet pick up when the switch is closed
Ans: Cube C and D
(ii)Suggest two changes that could make the magnet stronger
1. Increasing current
2. Increasing number of coils
55. (a)Fig 4.1 shows a transformer connected to a power supply and a
milliammeter.
(i)What type of transformer is this?
Ans: Step up transformer
(ii)Explain why the milliammeter deflects momentarily when the switch is
closed
Ans: When the switch is closed, an EMF is induced in the secondary coil and as
such the galvanometer deflects momentarily
(iii)Explain why there is no deflection when the switch remains closed
Ans : with a steady current in the circuit, no EMF is induced because the
magnetic field is not changing.
(iv)
A 240V a.c source replaces the supply shown in Fig 4.1. Calculate the
output voltage.
Formula :
𝒙
𝟐𝟒𝟎𝑽
=
𝟏𝟎𝟎𝟎𝒙
𝟏𝟎𝟎𝟎
𝒐𝒖𝒕𝒑𝒖𝒕 𝒗𝒐𝒍𝒕𝒂𝒈𝒆
𝒊𝒏𝒑𝒖𝒕 𝒗𝒐𝒍𝒕𝒂𝒈𝒆
=
𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒕𝒖𝒓𝒏𝒔 𝒐𝒇 𝒔𝒆𝒄𝒐𝒏𝒅𝒂𝒓𝒚 𝒄𝒐𝒊𝒍
𝒏𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒕𝒖𝒓𝒏𝒔 𝒐𝒇 𝒑𝒓𝒊𝒎𝒂𝒓𝒚 𝒄𝒐𝒊𝒍
𝟐𝟎𝟎𝟎
𝟏𝟎𝟎𝟎
=
𝟒𝟖𝟎𝟎𝟎𝟎
𝟏𝟎𝟎𝟎
= 480V
(v)State the advantage of transmitting power at a high voltage
Ans: High voltage means low current, therefore leading to reduced loss of
power.
(b)Fig 4.2 shows a mains plug
(i)
Label the three wires
(ii)
Which wire could be connected to the metal body of an appliance
Ans: Earth wire
Explain why
Ans: The main function of the earth wire is to conduct the leaking current
from the electrical appliance to the ground
56. The equation shows decomposition of magnesium carbonate.
MgCO3 (s)
MgO(s) + CO2 (g)
(a)Calculate the mass of carbon dioxide formed when 0.1 moles of magnesium
carbonate is completely decomposed.
[ Ar : Mg = 24 , C = 12, O = 16 ]
Molecular mass of CO2 is : (12 + 16 × 2) = 44g/mol
So, mass = number of moles × molar mass
= 0.1 moles × 44g/mol
= 4.4g
(b)Magnesium carbonate reacts with dilute hydrochloric acid as shown by the
equation.
MgCO3 (s) + 2HCl (aq)
MgCl2 (aq) + CO2 (g) + H2O(l)
(i)How many moles of hydrochloric acid react with 1 mole of magnesium
carbonate?
Ans: 2 moles
(ii)Calculate the number of moles in 25cm3 of 0.1 mol/dm3 hydrochloric acid
Convert 25cm3 to dm3
Number of moles: concentration × volume
= 0.1 mol/dm3 × 0.025dm3
= 0.0025 moles
(iii)What volume of carbon dioxide would be produced when 0.1 moles of
magnesium carbonate completely reacts with dilute hydrochloric acid at room
temperature and pressure.
(1 mole of any gas occupies 24dm3)
1:1
0.1 : x
x = 0.1 moles
Volume = number of moles × 24dm3
= 0.1 moles × 24dm3
= 2.4dm3
57. Fig 7.1 shows a fractionating column used to separate the fractions of crude
oil
(a)(i)At which point, P, Q or R is the column at the lowest temperature?
Ans: R
(ii)Which fraction on the column contains the largest hydrocarbon molecules
Ans: Bitumen
(b)Crude oil is a mixture of alkanes which are saturated hydrocarbons. What
type of reactions do alkanes undergo?
Ans: addition reaction
(c)The fuel gas fraction contains the hydrocarbon propane, C3H8 , showing all
the bonds around all the atoms
(ii)Write a balanced equation for the burning of propane in a plentiful supply of
oxygen.
C3H8 + 5O2 (g)
4H2O(l) + 3CO2
(iii)When propane is burnt in a limited supply of oxygen a poisonous gas is
produced. Name the gas and explain how it is poisonous
Gas: Carbon monoxide
Explanation: Carbon monoxide is harmful when breathed because it displaces
oxygen in the blood and deprives the heart, brain and other vital organs of
oxygen
(d)When propane is passed over a hot catalyst, the molecule breaks down to
form hydrogen and an alkene.
(i)Name the alkene
Ans: Propene
(ii)Describe a test you would carry pout to distinguish an alkene from propane
Test: Bromine water test
Result for propane: bromine water remains orange when mixed with
alkanes and shaken
Result for alkene: bromine water turns colourless when mixed with alkenes
58. Sample of two different gases are allowed to diffuse through a small hole, in
air at room temperature and pressure. The time taken by each gas is shown in
Table 8.1
Gas
Time/ s
Relative molecular
mass
Ammonia
20
17
Nitrogen
26
28
(a)Use the periodic table to calculate the relative molecular mass of ammonia,
NH3. Write the answer in Table 8.1
(b)What is meant by diffusion?
Ans: Movement of particles from a region of high concentration to a region
of low concentration against a concentration gradient until even
distribution is attained
(c)Explain why, at the same temperature, Nitrogen takes longer than ammonia
to diffuse through a small hole
Ans: because of higher molecular mass, nitrogen diffuses slowly
(d)Suggest what would happen to the time taken for the ammonia sample to
diffuse if the temperature was dropped to 10°C
Ans: increase in time taken
Explanation: Lower temperatures decrease the energy and therefore the
movement of the molecules, decreasing the rate of diffusion.
59. Fig 9.1 shows how two hormones A and B control the levels of glucose in
the blood.
(a)Identify hormones A and B
A: insulin
B : glucagon
(b)Name the gland that produces hormone A and B
Ans: Endocrine gland
(c)How does the presence of hormone A lead to a drop in glucose level
Ans: Hormone A signals the liver to take up glucose and store it as
glycogen
60. Fig 10.1 shows the parts of the digestive system
(a)Identify the blood vessel G
Ans: Hepatic artery
(b)Why is there a lesser amount of amino acids in the hepatic vein than in vessel
G?
Ans: deamination of amino acids takes place in the liver, thus leading to
less amount of them in hepatic vein
(c)Bile is an excretory product. State two advantages of releasing bile into the
duodenum
Ans: * Aids digestion by breaking down fats
•
•
Helps absorb fat soluble vitamins
Eliminate waste products
61. Fig 11. 1 shows a longitudinal section of a bean seed
(a)Name the structures P and Q
P : Plumule
Q: Radicle
(b)Describe how you would show that the cotyledons contains protein
Ans: Biuret solution is used to identify the presence of proteins. Biuret
reagent is a blue solution that , when reacts with protein will change colour
to pink – purple.
(c)Describe how structures P and Q are able to use the starch stored in the
cotyledons
Ans: The starch is converted to soluble sugars by the enzymes which
become active as soon as the seeds germinate and in this form it can be
transported by the phloem cells.
62.Fig 12.1 shows a longitudinal section of the heart
62. Fig 13.1 shows a commercial application of asexual reproduction
(a)Name this type of asexual reproduction
Ans: Grafting
(b)Why is this method regarded as asexual reproduction?
Ans: No seeds are required to produce a new plant
(c)Give two reasons why the bark around the cut surfaces is covered with grease
1. To exclude air
2. To slow down loss of water
(d)Why is it important for the woody parts of the scion and the stock to be in
contact before tying the two together?
Ans:
63. Fig 14.1 shows how the pulse rate of a student changes during and after
vigorous exercise. The exercise took 5 minutes
(a)Explain why the pulse rate increases during the early stage of the exercise
Ans: The heart must beat faster during exercise because by increasing the
heart rate, the body is able to increase cardiac output and deliver the
necessary blood flow to the muscles. During exercise the body's muscles
increase their activity level and consume more oxygen.
(b)Explain why the pulse rate does not return to normal immediately after the
exercise
Ans: After the exercise the heart needs to reduce the pulse rate slowly until
it is back to normal. The pulse rate does return immediately because blood
is still moving around the body at a relatively high pressure.
64. A boy drops a stone of mass 0.5kg into a well. The stone takes 2 seconds to
reach the bottom of the well( g = 10N/kg)
(a)Calculate the depth of the well
g=
h=
h=
2ℎ
𝑡2
𝑔𝑡 2
2
10 × 22
2
h = 20m
b)Calculate the kinetic energy of the stone just before it reaches the bottom of
the well.
k.e = g.p.e
= mgh
= 0.5kg × 10m/𝑠 2 × 20m
= 100 joules
c)Calculate the velocity of the stone just before hitting the bottom of the well
k.e =
𝑚𝑣 2
v=√
2
2 ×𝑘.𝑒
𝑚
200
v =√ 0.5
2×100𝐽
v = √ 0.5𝑘𝑔
v = 20m/s
(d)What assumption did you make in answering (b)? (repeated question, search
for the answer in the previous questions)
Ans:
(e)If a boy now drops a 1.0kg stone into the well, how would the value of the
kinetic energy compare with your answer in (b)?
Ans: The kinetic energy would be twice the amount in (b)
64. A student performs an experiment to determine the period of a simple
pendulum. She uses a stopwatch to record the time taken for 20 oscillations. Fig
2.1 shows the face of a stopwatch.
a) What is the time recorded by the stopwatch?
Ans: 15 seconds
b) Calculate the period of the pendulum
Ans: period =
=
𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑜𝑠𝑐𝑖𝑙𝑙𝑎𝑡𝑖𝑜𝑛𝑠
15𝑠𝑒𝑐𝑜𝑛𝑑𝑠
20
period= 0.75
(c)State one factor that would affect the period of the pendulum
Possible Answers: the length of the string, the mass of the bob, and the angle
displaced.
Additional information : The length of the string affects the pendulum's period
such that the longer the length of the string, the longer the pendulum's period.
(d)After some time, the pendulum would stop oscillating. Give a reason for your
answer
Ans: pendulum stops oscillating because it loses energy when it is converted
into heat. Even without air friction, the friction which exists with the point
around which the pendulum rotates causes the system to lose kinetic energy
and eventually stop
65. (a)A hot metal block is immersed in a beaker containing 500g of water. The
temperature of water rises to 20°C. Calculate the amount of heat energy gained
by water. (specific heat capacity of water = 4200J/kg°C)
Energy transferred = mass × specific heat capacity × temperature change
= 0.5kg × 4200J/kg °C × 20°C
= 42 000 J
66. Fig 5.1 shows the charge on a balloon after it has been rubbed with a woolen
cloth
(i)Explain why the balloon becomes negatively charged
Ans: Rubbing the balloon with a cloth transfers electrons from the cloth to the
balloon so the balloon now has an excess of electrons and it is negatively
charged.
(ii)Explain why the balloon is attracted to the woolen cloth
Ans: as the balloon is rubbed against the woolen cloth, the cloth becomes
positively charged and as the balloon is negatively charged it will become
attracted to the cloth.
(b)Fig 3.2 shows a plastic rod brought near a metal cap of positively
charged gold leaf electroscope. The divergence of the leaf increases
(a)What is the charge on the plastic rod?
Ans: Positive
Additional information on pictures below
(ii)The plastic rod is taken away, and the cap of the electroscope is touched with
a finger. What will be observed?
Ans: The leaf closes
Explain your answer
Ans : When we touch the metal top of an electroscope, some amount of
charge will be transferred to our body. Because metal top and our body
both are conductors, will try to come to a common potential.
67. Fig 6.1 shows two bulbs connected in a circuit with a battery and two
ammeters. Ammeter A reads 2A and Ammeter A1 reads 0.5A
Calculate:
(a)The current through the 2Ω bulb
2A – 0.5A = 1.5A
(b)The potential difference across the 6 Ω bulb
Potential difference = current × resistance
p.d = 0.5A × 6Ω
= 3V
(c)What is the potential difference across the battery?
Calculate the total resistance first
1
𝑅𝑇
1
𝑅𝑇
1
=
1
+6
2
4
=6
RT = 1.5Ω
P.D across the battery would be current × resistance
= 2A × 1.5Ω
= 3V
Hint : Use 2A current because Ammeter A is connected directly to the
battery
68. The equation shows how calcium carbonate reacts with hydrochloric acid
CaCO3 + 2HCl
CaCl2 + H2O + CO2
(a)Calculate the relative molecular mass of calcium carbonate. Use the periodic
table
Ca = 40 ; C = 12 ; O = 16 × 3 (add all of them to get 100)
= 100g/mol
(b)(i)Calculate the mass of carbon dioxide produced when 25.0g of calcium
carbonate reacts with excess hydrochloric acid
Number of moles of CaCO3 =
𝟐𝟓.𝟎𝒈
𝟏𝟎𝟎𝒈/𝒎𝒐𝒍
= 0.25 moles
1 mole of CaCO3 produces 1 mole of CO2 , therefore we use ratio to find the
moles of CO2
mass of CO2 will be number of moles × molar mass.
= 0.25 moles × 44g/mol
= 11g
(ii)Calculate the volume occupied by the mass of carbon dioxide in (b)(i)
measured at room temperature and pressure
v = 0.25 moles × 24 dm3
= 6dm3
69. The diagram shows how a door handle was electroplated with copper
(a) Complete the statement below using some words in the diagram
In the electrolytic cell the door handle is connected as the cathode and the
electrolyte is aqueous copper(ii) sulphate.
The process was carried out for 2 hours
(b)Describe the appearance of each of the following after 2 hours
(i)electrolyte
Ans: remains blue
(ii)copper rod
Ans: lost mass/ became thin
(c)Explain why the colour of the solution does not change (answer available in
the previous questions)
Ans:
(d)Write ionic equations for the anode and the cathode reactions (answer also
available in the previous questions)
Anode:
Cathode:
70. The chemical equation represents the process of photosynthesis
The reaction proceeds in stages. Bonds between atoms in reactant molecules
have to be broken and then new bonds formed between atoms in the product
molecules. Use this information to explain why the reaction is endothermic
Ans: In the reaction, sunlight is absorbed by chlorophyll in order for the
reaction to proceed.
71. The structure of a macromolecule, nylon, is shown.
(a)What is a macromolecule?
Ans: A macromolecule is a very large molecule, such as protein, commonly
composed of the polymerization of smaller subunits called monomers.
Proteins are also macromolecules. The structure of a protein is shown
(b)Write one similarity and one difference between the structures of nylon and
the protein
(i)similarity : the have the same linkage which is the amide linkage
(ii)difference: Protein has enormous range of structures and properties
while nylon has regular structure and regular properties.
(iii)Name the types of compounds produced by the hydrolysis of proteins
Ans: amino acids
(c)What are the products of the hydrolysis of fats?
Ans: Glycerol and fatty acids
72. Nitrogen is used for making ammonia in the Haber process
(a)Suggest a reason why oxygen should be removed from nitrogen in air before
the nitrogen is used.
Ans: To prevent it (oxygen )from reacting with hydrogen thus forming
water .
(b)(i)Name one acidic oxide of nitrogen formed in car engines
Ans: Nitrogen oxide
(ii)What is the purpose of catalytic converter in a car exhaust system?
Ans: Catalytic converters are used in exhaust systems to provide a site for
the oxidation and reduction of toxic by-products (like nitrogen oxides,
carbon monoxide, and hydrocarbons) of fuel into less hazardous substances
such as carbon dioxide, water vapor, and nitrogen gas.
72. Fig 12.1 shows the laboratory preparation of chlorine
(a)(i) Name the solid labelled X
Ans: potassium permanganate
(ii)What is the purpose of the water in the test tube?
Ans: dissolve any hydrogen chloride fumes
(b)What is the colour of chlorine gas ?
Ans: yellowish green
(c)Chlorine reacts with water as shown by the equation
(i)Name the two products for the reaction
Ans: Hypochlorous acid and hydrochloric acid
(ii)One of the products is a bleaching agent. Write the formula of this product
Ans: HOCl
73. Describe a chemical test for the presence of aluminium ions, Al3+ , in an
aqueous solution
Test: add a few drops of sodium hydroxide and a white precipitate will be
formed, then add excess sodium hydroxide
Positive results: white precipitate is formed which is soluble in excess
74.An experiment was carried to investigate the activity of the enzyme amylase.
Two test tubes, P and Q were set up, each containing equal volumes of amylase,
its substrate and either an acidic or alkaline solution, as shown in Fig 14.1
Samples from test tubes were tested for starch at the start of the experiment. The
test tubes were then placed in a water bath kept at 35°C for one hour. The
contents were tested for starch again. The results are as shown in Table 14.1
Tube
Start of experiment
End of experiment
P
Blue – black
Blue – black
Q
Blue – black
Brown
(a)Name the reagent that was used to test for starch
Ans: Iodine solution
(b)(i)In which test tube would the contents test positive for reducing sugar at the
end of the experiment?
Ans: Tube P
(ii)Explain your answer to (i)
Ans: Colour for positive test of reducing sugar is blue – black
(c)What factor was being investigated in the experiment?
Ans: Effect of temperature on enzyme activity
(d)Name a part of the alimentary canal where amylase acts
Ans: small intestine (duodenum)
75. Fig 15.1 shows variation in oxygen concentration, number of bacteria and
fish in a river a distance of 50km from point P, which is up stream from a
source of pollution.
(a)At what distance from P did the river become polluted?
Ans: 10km
(b)With reference to the three curves on Fig 15.1, state the effect of pollution on
the following:
Concentration of dissolved oxygen
•
Pollution lowers the quantity of dissolved oxygen
Numbers of fish
•
Number of fish reduces due to pollution
Numbers of bacteria
* Bacteria multiplies in number due to pollution
(c)Explain why the numbers of bacteria started decreasing after a distance of
20km from point P.
Ans: There is less pollution at that point
76. Fig 16.1 shows the changes in numbers of three organism , X, Y and Z
in a pond between January and August
(a)Which organism has the largest numbers in June?
Ans: Z
(b)A pesticide was sprayed to kill organisms X
(i)Suggest in which month organism X was sprayed
Ans: March
(ii)Give a reason for your answer
Ans: The number of organisms started reducing by then
77. Fig 17.1 shows three cuttings from one plant placed in a tray of moist soil.
The tray and cuttings were covered with a polythene bag. The cuttings
developed into individual plants.
(a)What form of reproduction is represented in the diagram?
Ans: Asexual reproduction
(b)The clear polythene bag reduces water loss by evaporation
(i)Describe how polythene bag helps to reduce water loss through leaves of
stem cuttings
Ans: It slows down the rate of transpiration because it closes the moisture
in and increases humidity
(ii)Why is it better to use a clear plastic bag rather than a dark coloured one?
Ans: So as not to block sunlight which is necessary for photosynthesis
78. Fig 18.1 shows apparatus used to measure the rate at which a certain
gas is used
(a)Name the process under investigation
Ans: Respiration
(b)What is the purpose of soda lime in the test tube?
Ans: To absorb carbon dioxide
(c)After 20 mins would be coloured liquid move towards or away from the test
tube?
Ans: Towards the test tube
Explain your answer
The insect uses oxygen and soda lime absorbs carbon dioxide, so the
amount of cases keep on reducing inside the tube hence colored liquid move
towards the tube
79. Fig 19.1 shows two types of cells A and B
(a)Name the cells A and B
A: Root hair cell
B : Red blood cell
(b)Give two differences between cells A and B
A
B
1
Found only in plants
Found only in animals
2
Contains nucleus
Does not contain any nucleus
(c)For each cell A and B state its function and describe how it is adapted for the
named function
Cell A
Function : Transporting water and mineral salts from the soil to the plant roots
Adaptation : Root hair cells are adapted for taking up water and mineral
ions by having a large surface area to increase the rate of
Cell B
Function : The primary function of red blood cells is to transport oxygen
to body cells and deliver carbon dioxide to the lungs
Adaptation: they contain haemoglobin - a red protein that combines with
oxygen. they have no nucleus so they can contain more haemoglobin. they
are small and flexible so that they can fit through narrow blood vessels.
80. Fig 1.1 shows a simple pendulum which is swinging between the
extremities a and b
It takes 0.2s for the pendulum to swing from a to b
(a)Calculate the period of pendulum
Period = time taken / number of oscillations
= 0.2 / 1
= 0.2
(b)Calculate the frequency of the pendulum
Frequency = number of oscillations / time taken
= 1/ 0.2
=5
81. Fig 2.1 shows a metal ball
being dropped from the surface
of oil in a tube of length 2m. The
ball has a mass of 1kg, and it
moves with a constant
acceleration
(a)Calculate the resultant force
acting on the ball
Ans: 1kg × 10N/kg = 10N
(b)Calculate the friction caused by the oil (g = 10N/kg)
Ans: The friction is 10N also since the ball is accelerating constantly
(c)Calculate the time taken by the ball to reach the bottom of the tube
g =
t=√
𝟐𝒉
𝒕𝟐
t=√
𝟐𝒉
𝒈
𝟐×𝟐𝒎
𝟏𝟎
t = 0.63 seconds
82. Fig 3.1 shows a set up used to investigate heat radiation. The heater is
placed an equal distance from each of the two identical metal plates. One plate
is painted all over with black paint on both sides and the other is painted shiny
on both sides. A coin is stuck at the back of each metal plate level with the
heater.
(a)Why is the heater placed at an equal distance from each of the metal plates?
Ans: so that they can receive the same amount of heat
(b)The coin on the plate on the right drops off after a few minutes. The coin on
the plate on the left drops a few minutes later.
Explain what is happening
Ans: The plate on the right absorbs heater better than the plate on the left
therefore that is why the coin on the right plate falls first
83. Fig 4.1 shows a rectangular glass block PQRS with a light ray incident on
the side PS at an angle of incidence of 60°. The ray continues through the glass
block as shown to emerge from side QR. The refractive index is 1.50 and the
critical angle is 42°
(a)Calculate the angle of refraction on side PS. Show your working
90° – 60° = 30°
84. (a)Fig 5.1 shows an arrangement used to compare the penetrating powers of
three radioactive emissions W, X and Y.
Identify emissions W, X and Y
W:Alpha
X : Beta
Y : Gamma
(b)Give one medicinal use of radioactivity
Ans: To diagnose and treat cancer tumors , to sterilize medical equipment
(c)Which of the radioactive emissions W, X and Y is the least ionizing?
Ans: Y
(d)State one source of background radiation
Ans: Rocks
85. Fig 11.1 illustrates the changes in adrenaline concentration in blood before,
during and after a 100 metre race.
(a)Describe what happens to the adrenaline concentration between 4 and 12
seconds
Ans: It increases
(ii)Suggest three effects of the change in (a)(i) on the muscles
•
•
•
More oxygen is sent to the muscles
More blood is sent/ redistributed to the muscles
Blood glucose levels also increase in order to produce enough energy to
sustain the body during training
b)(i)Name a hormone which has a similar effect to adrenaline but that usually
acts for a longer period of time
Ans: Cortisol
(ii)When is the hormone in (b)(i) secreted in larger amounts?
Ans: in the morning
86. Fig 12.1 shows the relationship between the circulations of the mother and
the foetus
(a)Name two substances that are at a higher concentration in the umbilical
artery than in the umbilical vein.
* Deoxygenated blood
* waste products
(b)Describe how oxygen is transferred from the mother’s blood to the foetus’
blood
Ans: Oxygen and nutrients from the mother's blood are transferred across
the placenta to the fetus through the umbilical cord. This
enriched blood flows through the umbilical vein toward the baby's liver
(c)State three structural differences between umbilical artery and umbilical
vein.
Umbilical artery
Umbilical vein
•
Thick, elastic, muscular walls
Thin walls with few elastic fibres
•
Do not have any valves
Have valves
•
Small lumen
*Large lumen
87. Fig 14.1 shows steps followed in the industrial production of sour
milk(Madila)
(a)What is the purpose of heating the milk?
Ans: To kill microbes
(a) Identify microorganism W
Ans: Bacteria
(b) Suggest one reason for refrigerating madila after packaging
•
To slow down growth of spoilage bacteria
(d)Explain why low fat madila is recommended as part of heathy diet
Ans: Fermented milk also seems to help lower blood pressure, lower
cholesterol, and prevent cancer from growing
89. (a) Define a drug
Ans: A drug is any substance that causes a change in an organism's
physiology or psychology when consumed
(b)Fig 15.1 shows a bottle containing whisky
(i)Identify the drug contained in the whisky
Ans: alcohol
(iii)
•
•
State two effects of this drug on the body
Alcohol can cause liver disease
It also weakens the immune system
(c)A person continues taking a drug until he can no longer do without it. Which
term describes this condition?
Ans: dependence
90. Describe how solids conduct heat
Ans: Conduction transfers heat energy in solids. The moving particles of a
warm solid material can increase the heat energy of the particles in a
cooler solid material by transferring it directly from one particle to the
next.
(b)An iron rod and a copper rod of similar dimensions are heated from the same
source. Complete table 3.1 to show whether the listed quantities of the rod will
increase, decrease or remain the same during the heating process
Quantity
How it affects
Mass
Remain the same
Volume
Increases
Density
decreases
(c)Fig 3.1 shows a bimetallic strip made of brass and copper before heating and
after heating
(i)Why does the strip bend during heating?
Ans: One metal expands faster than the other thus growing longer and end
up bending the other
(ii)Give one use of bimetallic strip
Ans: switches as thermostats
91. Fig 4.1 shows an alternating current generator
(a)Name the parts labelled X and Y
X : slip ring
Y :carbon brushes
(iii)Draw an arrow on the diagram to show the direction of the induced current
in the coil when it is in the position shown in the diagram.
92. What is background radiation?
Ans: Background radiation is a measure of the level of
ionizing radiation present in the environment at a particular location which
is not due to deliberate introduction of radiation sources.
(b)A particle emitted by a radioactive substance has two protons and two
neutrons.
(i)Name the particle emitted
Ans: Alpha
(ii)What is the charge of the emitted particle?
Ans: +2
(c)State two uses of radioactive substances
* Radioactive sources are used to study living organisms, to diagnose and
treat diseases, to sterilize medical instruments and food, to produce energy for
heat and electric power, and to monitor various steps in all types of industrial
processes
93. Fig 6.1 shows an experimental set -up to investigate the rate of diffusion of
hydrogen chloride , HCl and ammonia NH3 . Damp blue and red litmus papers
were both placed at position Y
(a)Name the process by which the gases move from the cotton wool to meet at
position X
Ans: diffusion
(b)(i)Calculate the relative molecular mass of ammonia , NH3
(refer to previous questions)
(ii)The relative molecular mass of hydrogen chloride is 36.5. Explain why the
position X where the gases meet is nearer to the hydrochloric acid end of the tube.
Ans: ammonia diffuses faster than hydrogen chloride gas because of its little
molecular mass therefore it reaches the hydrochloric acid side quickly
(iii)What colour change will be observed in the litmus paper at position Y?
Ans: The damp red litmus paper would turn blue (because of ammonia ) and
the damp blue litmus paper will turn red (because of hydrogen chloride gas
)
(iv)Why are damp litmus papers used instead of dry litmus papers
Ans: To enhance movement of ions
93. (a)Table 8.1 gives information about some organic compounds
(i)Complete the table by writing in the missing information in the blank spaces
Name
Structural formula
Homologous
series
Ethanol
Alkanol
Butane
Alkanes
(ii)Draw the structural isomer of butane
(b)Ethene reacts with hydrogen by an addition reaction
(i)Explain why ethene undergoes an addition reaction instead of substitution
Ans: because alkenes are a more unstable structure than alkanes, and it
takes more energy to break off bonds that are already there than to simply
form new ones.
(ii)State two conditions for this reaction and suggest a reason for each condition
Condition 1: Presence of catalyst
Reason : To speed up the reaction
Condition 2: a temperature of 150°C
Reason: To break up the double bond with ease
(iii)Name the product formed when hydrogen is added to ethene
Ans: Ethane
(c)Alkenes polymerize through addition polymers. Complete the table by using
an example of a polymer of your choice
Name of Structure of polymer chain showing three Structure
polymer monomer units
monomer
of
Protein
94. Fig 10.1 shows a developing mammalian foetus
Umbilical cord
(a)On Fig 10.1 label the structure X
(b)State the function of structure Y
The placenta serves as an interface between the mother and the developing
fetus and has three main jobs: Attach the fetus to the uterine wall.
Provide nutrients to the fetus. Allow the fetus to transfer waste products to
the mother's blood.
(c)Fig 10.2 shows a cross section through structure X
(i)Which blood vessel is a vein?
Ans: Q
(ii)Give a reason for your answer in (c)(i)
Ans: Has a large lumen
(iii)Name two substances transported in high concentration in blood vessel Q
*Oxygen
* Soluble food substances
95. Fig 12.1 shows the relationship between humidity and transpiration rate
(a)At what time of the day is the transpiration the highest?
Ans: 1200hrs
(ii)Explain how humidity affects the rate of transpiration
Ans: As the relative humidity of the air surrounding the plant rises the
transpiration rate falls. It is easier for water to evaporate into dryer air than
into more saturated air.
(b)Give two other environmental factors that affect the rate of transpiration
* Wind speed
*Temperature
96. Fig 14.1 shows a visking tube containing a mixture of two solutions and a
beaker containing water
Contents of the beaker and visking tube were tested using iodine solution and
Benedict’s solution. The results are shown in Table 14.1
Water in a beaker
Iodine test
Benedict’s test
yellow
Blue
Contents of visking Blue - black
tubing
Brick – red
(a)Identify the two solutions in the visking tube
* Starch
*Glucose
(b)Explain why the water in the beaker turned brick – red when tested with
Benedict’s solution after 30 minutes
Ans: The water contains molecules of simple sugar being glucose
(c)The mixture in the visking tube was replaced by a mixture of starch and
amylase and left for 30 minutes in a water bath at a temperature of 35°C
(i)Predict the result for iodine test in the tube after 30 minutes. Give a reason for
your answer
Prediction: a brick red colour will be observed
Reason: amylase has digested starch so there is no starch in the solution, but
glucose is present
(ii)Where in the alimentary canal does a similar reaction occur?
Ans: small intestine
97. Fig 15.1 shows a relationship of a receptor, neurone and effector organ
(a)Name the neurone in the Central Nervous System that links neurones A and B
Ans: Relay neurone
(b)A person touches a hot plate and quickly removes his hand
Name the receptor and effector in this action
Receptor: skin
Effector :muscle
(c)How is the mode of transmission of messages in Fig 15.1 different from
hormonal transmission?
Ans: the endocrine system uses chemical signaling (hormones, produced by
glands) while the nervous system uses electrical signaling (neural impulses).
98. A crane is used to lift a load of 1000N with a constant speed as shown in Fig
1.1
The load takes 15 seconds to lift by 3 metres
(a)Calculate the speed of the load
Ans: speed = distance / time
= 3m / 15s
= 0.2m/s
(b)State the tension, F, in the rope
Ans: 1000N
(c)Calculate
(i)the work done in lifting the load by 3 metres
Work done = Force × distance moved
= 1000N × 3m
= 3000Nm or 3000 joules
)ii)the power output of the crane while lifting the load
Power = work done / time taken
= 3000Nm/ 15s
= 200W
99. Fig 3.1 shows a ray of light entering a parallel sided glass block
(a)Complete the path of ray in Fig 3.1
(b) (i) State the value of angle of incidence of the ray on the block
Ans: 30°
(c)Fig 3.2 shows a ray of light entering a semi – circular glass block of refractive
index 1.5
(i)Explain why the ray does not bend when it enters the glass block
Ans: the incoming ray is perpendicular to the surface, so it is not refracted
(ii)Calculate the critical angle of the glass block
Ans: 90° – 50° = 40°
(iii)How will the ray proceed when it reaches side AB?
Ans: (shown by the arrow)
100. Fig 4.1 shows 2 resistors connected in series. The reading of the voltmeter
V1 is 6V and the reading of voltmeter V2 is 4V
(a)Calculate the voltage drop across the 4Ω resistor
Important note: Voltage applied to a series circuit is equal to the sum of the
individual voltage drops." This simply means that the voltage drops have to add
up to the voltage coming from the battery or batteries. 6V + 6V = 12V.
So, the answer is 6V – 4V = 2V
(b)Calculate the current through the resistors
IMPORTANT NOTE: In a series circuit, the current that flows through each of
the components is the same.
So current = 2V / 4Ω = 0.5 A
101. Fig 5.1 shows the industrial method of gauging the thickness of paper
using beta particles
(a)State the nature and charge of beta particles
Nature : Beta particles are high-energy, high-speed electrons or positrons
emitted by certain fission fragments or by certain primordial radioactive
nuclei such as potassium-40.
Charge : – 1
(b)The measurement of the paper thickness is used to control the pressure
applied by the rollers so that the thickness of paper produced is kept as constant
as possible.
Table 5.1 shows the changes that can happen when the paper passes through the
rollers
Complete Table 5.2 using the words increases or decreases
Thickness of paper
Radiation detected
Pressure applied by
rollers
Increases
Decreases
increases
Decreases
Increases
Decreases
102. Fig 13.1 shows two white blood cells P and Q which destroy bacteria in the
human body
(a)Identify the cells P and Q
P : phagocytes
Q : Lymphocytes
(b)Describe how each cell destroys bacteria
P : Engulfs and destroys bacteria
Q : They recognize proteins on the surface of pathogens called antigens . ...
If they do, they clone themselves in order to make enough antibodies
to destroy the pathogen.
(c)Describe how blood clotting occurs
Ans: Platelets immediately begin to adhere to the cut edges of the vessel
and release chemicals to attract even more platelets. A platelet plug is
formed, and the external bleeding stops
(d)Name two substances other than oxygen and carbon dioxide which are
transported by blood
1. Urea
2. Digested food molecules
103. A copper rod and a Perspex rod are each rubbed with a cloth. The Perspex
rod becomes positively charged and the copper rod remains uncharged
(a)Explain why copper cannot be charged by rubbing
Ans: Copper rod cannot be charged easily by friction because it is a conductor.
Only non-conducting materials can be charged easily by friction.
(b)What happens during the rubbing of Perspex that makes it to be charged
Ans: By rubbing the perspex rod by the dry cloth, electrons are transferred
from the surface of the perspex rod towards the dry cloth. So,
the perspex rod loses the electrons and they are transferred to the dry cloth
and becomes positively charged
104. Fig 6.1 shows hydrogen gas being passed over heated copper (II) oxide
to produce copper
(a)Name the type of reaction that takes place in fig 6.1
Redox reaction
Explain your answer
Copper (ii) Oxide reacts with hydrogen to form copper
(b)An incomplete equation representing the reaction taking place in Fig 6.1 is
shown
Cu(s) + H2 (g)
Cu(s) + H2O (l)
(ii)One of the products of reaction is water. Describe the chemical test for water
Test: Cobalt(II) chloride paper test
Result: This turns pink in the presence of water
(c)Other than the method used in Fig 6.1 state another method of producing
copper
Ans: Electrolysis
106. Magnesium Sulphate is soluble in water
(a)Describe how crystals of magnesium sulphate are made using magnesium
oxide powder and sulphuric acid as reactants
Ans: Magnesium oxide reacts with sulphuric acid to form magnesium
sulphate and water. The solution is then dried to remove water and only
magnesium sulphate crystals remain
(b)A sample of water containing magnesium sulphate is hard
(i)Name this type of hardness of water
Ans: permanent hardness
There are two types of hardness – temporary hardness and
permanent hardness.
•
Temporary hardness – also called 'Carbonate hardness'. ...
•
Permanent hardness, also referred to as 'non-carbonate hardness; is
the hardness due to the presence of calcium or magnesium sulfates,
chlorides and nitrates.
(ii)State the observation made when soap is shaken with hard water
Ans: a lather is formed
(iii)Give one method of removing this type of hardness of water
Ans: treating the water with washing soda.
(iv)Describe a chemical test to confirm the presence of the sulphate ions in the
sample
Test: Sulphate ions in solution, SO 4 2 -, are detected using
barium chloride solution. The test solution is acidified using a few drops of
dilute hydrochloric acid, and then a few drops of barium chloride solution
are added.
Result : A white precipitate of barium sulphate forms if sulfate ions are
present
107. The structure of an organic compound X is
(a)What is the molecular formula of the compound X?
Ans: C5H10
(b)What is the empirical formula of compound X?
Ans: CH2
(c)(i)To which homologous series does compound X belong?
Ans: Alkenes
(ii)Name another compound that belongs to the same homologous series as
compound X.
Ans: Ethene, Propene, Butene,
(d)(i)Name two products formed when compound X burns completely in air
1. Carbon dioxide
2. water
(ii)What other type of reaction can compound X undergo?
Ans: addition reaction
108.Mpho stuck pieces of blue cobalt chloride paper on the upper and lower
parts of a leaf. Each piece of paper was completely covered by a transparent
sticky tape to prevent any air reaching it as shown in Fig 11.1. Cobalt chloride
paper is blue when dry and turns pink when wet.
The paper on the lower surface turned pink before the paper on the upper
surface
(a)Which process caused the colour change of the cobalt chloride paper?
Ans: Transpiration
(b)Explain why it was important for Mpho to make sure that no air could reach
the cobalt chloride paper
Ans: Air can contain moisture
(c)Suggest a reason why the paper on the upper surface took longer to turn pink
Ans: The upper side has less stoma
(d)Fig 11.2 shows the leaves of the plant in the morning and in the afternoon
Explain why the leaves of the plant are upright in the morning
Ans: the stoma of the leaf cells are turgid and firm
109. Fig 12.1 represents stages in which an enzyme controlled chemical
reaction may occur
(a)Define the term enzyme
Ans: A biological catalyst that speed up chemical reactions
(b)Suggest what Q and R in Fig 12.1 represent
Q : . Q enzyme.
R product
(c)State one property of enzymes illustrated in Fig 12.1
Ans: Substrate specificity. Enzyme molecules are not used during reactions
(d)The enzyme has an optimum temperature of 30°C .
Describe how enzyme activity changes as temperature increases from 20°C to
60°C
Ans: Enzyme are active at 20degrees and enzyme activity increases. As
temp increases enzyme activity increases up until optimum temp.. At the
optimum temp enzyme activity is at the highest point. After optimum temp
when temp increases enzyme activity decreases.. At 60 enzyme activity
stops coz enzymes are denatured due to high temperature
110. Street lamps are connected to a transformer which is supplied voltage from
a power station. Fig 2.1 shows the type of transformer the lamps are connected
to
(a)Name the type of transformer shown in Fig 2.1
Ans: step down transformer
(b)Explain how the voltage output to the streetlamps is produced
Ans: as the power is switched on the EMF is induced on the other coil
which is the secondary coil
(c)Fig 2.2 shows some identical street lamps connected in parallel
The potential difference across lamp A is 240V. Each lamp is marked 40W;
240V
(i)State the value of the potential difference across lamp B
Ans: 240V
Note : Voltage is the same across each component of the parallel circuit
(ii)Draw a simple circuit diagram to show how lamps are connected
(iii)Suggest one advantage of having the lamps in parallel
Ans: if one lamp goes out others remain lit
(iv)Calculate the energy, in joules, converted by each lamp in 12 hours
Ans: energy = power × time
12 hours = 43 200 seconds
= 40 W × 43 200s
= 1 728 800 J
(v)Calculate the resistance of each lamp. Use the equation (P)
R = V2 / P
R = (240)2 / 40
R = 1440 Ω
=
𝑽𝟐
𝑹
111. Sodium is an element in Group 1 of the periodic table. It has the electron
configuration of 2, 8, 1
(a)State why sodium is in Group 1
Ans: has one electron in the valence shell
(b)In which period is Sodium found?
Ans: period 3
Explain your answer
Ans: it has three shells
(c)State how the sodium atom reacts with atoms of non- metals
Ans: ionic bonding, it donates electrons to them in order to attain stability
112.Fig 8.1 shows a blast furnace used in the extraction of iron
(a)(i)Name the substance W
Ans: coke
(ii)At which position , X or Y is molten iron removed?
Ans : Y
Give a reason for your answer
Ans: It is denser, so it sinks while the waste products floats
113. (a)The poisonous gas, carbon monoxide is emitted by vehicle exhausts
(i)How is the gas formed
Ans: Incomplete combustion of petrol/ diesel
(ii)Explain how a catalytic converter reduces the emission this gas
Ans: Carbon monoxide is oxidized to carbon dioxide in the catalytic
converter
(iii)The following reaction is used to detect carbon monoxide
CO + Pd2+ + H2O
CO2 + Pd + 2H+
What type of chemical reaction is the change is the change Pd2+ to Pd? Give a
reason for your answer.
Ans: Reduction reaction because Pb has gained electrons
(iv)
Ethene will also give the above reaction. Describe another chemical test
for this gas
Ans: Bubble the gas through bromine water. Bromine water will change
colour from brown to colourless, or is decolorized
(c)Pure nickel is used to catalyze the reduction of unsaturated oils to saturated
fats
(i)What is meant by the terms saturated and unsaturated?
Ans: Saturated hydrocarbons have single bonds between carbons while
Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent
bonds between adjacent carbon atoms.
The term "unsaturated" means more hydrogen atoms may be added to the
hydrocarbon to make it saturated
(ii)Name the functional group in fats
Ans: esters
(iii)How can soap be made from fats
Ans: Hydrolyzing fats with concentrated sodium hydroxide
114. Propane is an alkane. It has the structural formula
Propane reacts with chlorine to form two chloropropanes with the formula
C3H7Cl
(i)Write the equation for this reaction
C3H8 (g) + Cl2 (g)
C3H7 Cl(aq) + HCl(aq)
(ii)What type of reaction is this?
Ans: Substitution reaction
(c)The two chloropropanes react with sodium hydroxide to form different
alcohols
(i)These alcohols are isomers. Using the propanols as an example explain the
term isomers
Ans: substances which have the same molecular formula but different
structural formulae
(ii)Fractional distillation can separate two propanols. Suggest a reason why the
method is effective
Ans: They have different boiling points
(iii)Propanol and propanoic acid react to form an ester. Give the name and
structural formula of the ester
Name: Propyl propanoate
Structural formula
(d)Propane can be made by heating propane and sulphur
(i)Outline another method of making alkenes from alkanes
Ans: cracking a long chain alkane at a temperature of 600°C using
aluminium as a catalyst.
(ii)Outline how propanol can be made from propene
Ans: expose propene to steam under high temperature in the presence of a
catalyst