2018_Combined science_olevel_nov_paper2

Extracted Content: 2018_Combined science_olevel_nov_paper2

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ZIMBABWE SCHOOL EXAMINATIONS COUNCIL
General Certificate of Education Ordinary Level

COMBINED SCIENCE 4003/2
PAPER 2 Theory

NOVEMBER 2018 SESSION 2 hours
Candidates answer on the question paper
Additional materials: Calculator (Optional)

Allow candidates 5 minutes to count pages before the examination.

This booklet should not be punched or stapled and pages should not be removed.

INSTRUCTIONS TO CANDIDATES

Write your name, centre number and candidate number in the spaces at the top.
Write your centre and candidate number in the boxes on the top right comer of
every page of this paper.

Check if the booklet has all the pages and ask the invigilator for a replacement if
there are duplicate or missing pages.

Write your answers in the spaces provided on the question paper.

Section A

Answer all questions.

Section B
Answer any two questions,

Section C
Answer any two questions.

Section D
Answer any two questions.

INFORMATION FOR CANDIDATES
The number of marks is given in brackets [ ] at the end of each question.

Copyright: Zimbabwe School Examinations Council, N2018.

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Section A Answer all questions in this section in the spaces provided.

Fig.1.1 shows a palisade cell.

nucleus

cell vacuole

Fig. 1.1

(a) (i) Identify structure P.

nj
(ii) Explain how the palisade cell is adapted for its function.
14]
(b) —_ State any two nutrient deficiency diseases in humans,
[2]

4008/2 N2018

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(a) Name any two types of teeth and give one function for each.

14]
(ib) @ Explain the importance of chemical digestion.

[2]
(ii) =~ State the enzyme that converts starch to maltose in the mouth.

|

Fig.3.1 shows the electrolytic cell used for the electrolysis of molten lead bromide.

battery

(a) —_ Define the term electrolysis.

2}

4003-2 N2O1N

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ib (i) State the name given to electrode A.

1)
(ii) = Name the product formed at electrode B.

1

(iii) ~~ Write an equation for the reaction which occurs at B.

[2]
Fig.4.1 shows a method used to completely neutralise sodium hydroxide solution, NaOH,,.).

Fig.4.1
(a) Name the method shown in Fig.4.1

1]
(b) Explain why the phenolphthalein indicator is added.

(2)

4003-2 N26t8

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{e)

(d)

(a)

(b)

Complete and balance the chemical equation for the reaction between sodium hydroxide
and sulphuric acid.

2NaOH + H)SQ, +
8]

Calculate the molecular mass of NaOH.

i
State Ohm’s law and give any one limitation to the law.

Ohm's law

Limitation ee

[2]

Fig.5.1 shows an electric circuit with three resistors, R, which is 2.0,
R> which is 20 and Rs which is 6 Q.

(i) State the way in which R, is connected in relation to Ry and Ry.

1]
(ij) = Calculate the total current, [, in the circuit.

B]

40042 N20

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(a) Fig.6.1 shows a water pump.

(i) Name the type of the water pump shown in Fig.6.1.

1]
(i) = Outline what happens during the upward stroke.

B]

40032 M2018

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(b) —_—- Fig.6.2 is a pie chart showing people using a particular source of energy.

Fig.6.2
(i) Identify the energy source which is most widely used.

fy

(ii) =~ Calculate the percentage of people using natural gas.

[2]

40082 N2018

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Section B Answer any two questions. Write your answers in the spaces provided on the question paper.

(a) —_—- Define the term pollination.

[2]
(b) —_ Explain the importance of coloured petals, sticky pollen grains and enclosed anthers of
an insect pollinated flower.
(4]
() fi State any two conditions necessary for germination.
[2]
(i) State any two advantages of reproducing plants using seeds over
vegetative propagation.
[2]

40032 N2018

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[4]

(1)

(a) —_—- Fig. 8.1 shows a sperm.
Fig. 8.1
ty) Explain how the structure of the sperm is related to its function,
(ii) Suggest why sperms need to be produced in large numbers compared to female gametes.
(b>) = @ State any two phases of the human menstrual cycle.

[2]

(i) ~—_— State the part of the female reproductive system where implantation of
the fertilised ovum takes place,

i

(iii) Name any two substances which move from the mother to the foetus
through the placenta.

[2]

4003/2 N2018

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(a) Fig.9.1 shows a food web in an ecosystem. decomposers small bird ———> bird of prey caterpillar —————» mouse ale onl Fig.9.1 (i) State what is represented by arrows between organisms. nM] (i) State the organism that feeds on all other organisms in the web. 1 (ili) State, with reasons, an organism in the web which could exist in small numbers. BR) (b) — Explain how a food web is a better representation of what happens in an ecosystem than a food chain. (1) (c) State any two activities of man that can be harmful to an ecosystem. [2] (d) — Give any two factors that reduce the rate of transpiration.

40042 N2018

[2]

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Section C

Answer any two questions. Write your answers in the spaces provided on the question paper.

10. (a) =§6(i) Define the term jydrocarbon.

(ii) Name any one homologous series under hydrocarbons.

(ili) From the homologous series named in (ii), name the hydrocarbon

with three carbon atoms.

(iv) Draw the displayed formula of the hydrocarbon named in (iii),

(b) —_ Biogas is a renewable fuel obtained from organic wastes.

(i) Describe how biogas is produced.

(1)

1)

0)

1)

(ii) — State the three conditions needed for optimum production of biogas.

11. Nitrogen and hydrogen gases were compressed in the reaction chamber at a
temperature of 450 °C_500 °C to produce ammonia.

(a) Describe what would happen to the yield of ammonia if the temperature of
the reaction chamber was raised to 800 °C.

40032 N2018

G]

13)

[2]

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(b)

(c)

(d)

(e)

State two optimum conditions for the Haber process other than temperature.

{2]
Explain why ammonia and other gases are recycled into the reaction chamber.

fl]

State any two industrial uses of ammonia.

Calculate the number of moles in 56 dm* of ammonia.

B]

4003-2 NIOLS

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12.

(a)

volume

of gas X/cm*

Fig.12.1 shows how the volume of gas X varied with time as a 2 cm piece of
magnesium ribbon reacted with dilute hydrochloric acid (HC/ ).

(i)

(ii)

(iii)

(iv)

30

oe ae

ae
TERRE RHE RS

time/ minute

Fig.12.1
Name gas X.

11]
From the graph, deduce the maximum volume of gas X produced at the end of
the reaction,

1h]
Determine the time taken for the reaction to get to completion.

1"

Describe the effect of using magnesium powder instead of the
magnesium ribbon to the rate of the reaction.

[2]

40032 N2018

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(b)

(v)

(ii)

State any two factors, other than surface area that would increase the
rate of reaction.

(2]
State an industrial process that produces nitrogen.

1

State any two uses of nitrogen.

(7)

4003-2 N2OLN

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Section D Answer any two questions. Write your answers in the spaces provided on the question paper. 13. (a) ~— A diesel engine undergoes a four stroke cycle during its operation. (i) Describe what happens during the intake stroke of the diesel engine.

13]
(ii) Explain why the diesel engine does not have spark plugs.
(2)
(pH A hand feels hot when placed above an electric heater which is switched on.
(i) Describe how the heat reaches the hand.
13]
(ii) Calculate the energy drawn by the electric heater if it is connected to
240 V mains supply and draws a current of 6 A for 1 minute.
[2]
14.) (a) A direct current (d.c) motor is a device which converts electrical energy to
kinetic energy.
(i) Describe how motion is produced in a d.c motor.
13)
(i) State any two factors that would affect the motion of the d.c motor.
[2]

(iii) State what would happen if the d.c power supply is replaced by alternating
current (a.c),

1]

40032 N2018

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(b) State any three precautions taken against lightning.

B]

(c) Name a device which can be used to determine whether or not a glass rod is
charged.

i
15. (a) ~~“ Fig.15.1 shows a 3-pin plug.

Fig.15.1
(i) State which of the labelled wires is the live wire.

1)
(ii) State the colours of wires A and C.
A
Cc
[2]
(iii) = State any one advantage and any one disadvantage of using photo
voltaic cells as a source of electricity.
advantage
disadvantage
12]

4003-2 N2O1L8

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(iv) Explain how photo voltaic cells are used as a source of electrical power for appliances which use both alternating current and direct current.

[4]
(b) State any one use of electricity in the home.

Cy

40032 N2018

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