IGCSE Combined Science (Extended)
Half Yearly Examination – Mock Question Paper
Time: 1 hours 15 minutes
Marks: 120/160 good
Advice: 1. Writing non-exam wording
2. Missing keywords
3. Careless calculation mistakes
4. Leaving answers incomplete
Instructions
Answer all questions.
2. Write your answers clearly in the spaces provided.
3. Use a black or dark blue pen.
4. You may use a calculator.
5. Show all working in calculations.
6. The total marks for each question are shown in
brackets [ ].
1.
Question 1
(a)
State two differences between plant cells and animal
cells.
1. Plant cell have choroplast
2. Plant cell has a larger vacule
[2]
1
(b)
A student observed a cell under a microscope.
The actual length of the cell was 0.08 mm.
The image length was 64 mm. Calculate
the magnification.
Answer: 800
[2]
(c)
Explain why specialised cells are important in
multicellular organisms.
It allows the organism to carry out a specific task quicky
and it is efficient. It reduces the work done for the other
organs.
[3]
(d)
(i)
The diagram shows part of the human digestive
system.
Name the organ where most absorption of digested
food occurs.
2
Answer: Small Intestine
(ii)
Describe two adaptations of this organ for absorption.
1. Aborbs water
2. Aborbs minerals
[3]
Question 2
(a)
Define diffusion.
Diffusion is when the particles move from a higher
concentration region to a lower concentrated region.
[2]
(b)
(i)
A student placed potato cylinders into different sugar
solutions.
Concentration of
sugar solution / %
Change in
mass / g
0
+4.2
5
+1.8
10
0
15
–2.6
20
–5.0
State the concentration that is isotonic to the potato
3
cells.
Answer: 10
Explain why the potato cylinders lost mass in 20%
sugar solution.
The water in the potato lost water through osmosis as
osmosis takes take when the Higher water potential move
to a lower water potential which is the concentrated
solution. The pototo had more mass at the start than in end
since water was lost.
(ii)
[4]
4
(c)
Explain the importance of active transport in root hair
cells.
Active transport carries protiens from a lower concentration
to a higher concentration.
[3]
Question 3
(a)
Name the enzyme that digests:
(i)
proteins
(ii)
starch amylases
Protease
[2]
State the products of fat digestion.
Fatty acids and glycerol
[1]
(b)
Explain how the structure of villi increases the rate of
absorption.
Walls are thin, reducing diffusion distance. Rich blood
supply maintains concentration gradient. Lacteals absorb
fatty acids and glycerol.
(c)
[4]
5
(d)
(i)
(ii)
A person’s diet contains a very low amount of iron.
State one disease caused by iron deficiency.
Lack of blood
Describe two symptoms of this disease.
1. Faint
2. Lack of blood when u get a cut
[3]
6
Question 4
(a)
Name the blood vessel that carries blood:
(i)
from the heart to the lungs
pulmonary artery
(ii)
from the lungs to the heart
pulmonary vein
[2]
Describe the function of red blood cells.
It carries oxygenated blood from lungs to heart and then to
rest of body. It don’t have nucleus to maximis uptake of
blood. It has a large surface area
(b)
[2]
(c)
Explain why arteries have thick muscular walls.
To withstand high blood pressure from heart and it allows
the blood to flow through smootly
[3]
The graph shows heart rate during exercise.
(i) State the effect of exercise on heart rate.
Increase
(d)
(ii)
Explain why heart rate changes during exercise.
During exercise the muscle need more energy so the
rate of aerobic respiration increase making the heart to
pump more blood and glucose
[4]
7
Question 5
(a)
State the word equation for aerobic respiration.
Oxygen + Glucose carbon dioxide + water
[2]
(b)
explain why breathing rate increases during exercise.
It increase rate of reaction because the body needs more
oxygen as it is doing more exercise. So the respiration
increase providing more energy to the body
[3]
(c)
Describe two differences between inhaled air and
exhaled air.
1. Inhaled air has more oxygen than carbondioxide.
2. Exhaled air has more carbondioxde than oxygen
[2]
(d)
Smoking damages alveoli.
Explain how this affects gas exchange.
It damages the alveoli decreaseing the surface are of the
intake of oxygen into the body and the body will have more
carbondioxide.
[4]
8
Question 6
Describe the arrangement and movement of particles in
a gas.
Gas is widely spread aprat it has larger intermolecular
space and the move at random direction and doesn’t
have a regular pattern
(a)
[3]
(b)
State the relative charges of:
(i)
proton
+
(ii)
neutron
nothing
(iii)
electron -
9
[3]
An atom has proton number 17 and nucleon number
35.
(c)
(i)
State the number of protons.17
(ii)
State the number of neutrons.18
(iii)
State the electronic configuration. 2,8,1
[3]
Question 7
(a)
Define relative atomic mass.
Atomic mass is the total number of protons and neutrons in
the nucleus of an atom
[2]
(b)
Calculate the relative formula mass
10
of calcium carbonate, CaCO3. (Ar: Ca
= 40, C = 12, O = 16)
Answer:100
[2]
(c)
Magnesium reacts with oxygen.
2Mg + O2 → 2MgO
Calculate the mass of magnesium oxide formed when 12
g of magnesium reacts completely with excess oxygen.
(Ar: Mg =
24, O =
16)
Answer:20
[4]
Explain why using a catalyst increases the rate of
reaction.
Answer: Using a catalyst decrease the activation energy
in the reaction. It allows more particles to have enough
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energy to react. It increase the susccesful collision
[3]
Question 8
State the test for hydrogen gas.
Lighted splint making a pop sound
(a)
[1]
(b)
Describe what is meant by an exothermic reaction.
It is the release of energy to the surrounding.
[2]
(c)
Zinc reacts with dilute hydrochloric acid.
Zn + 2HCl → ZnCl2 + H2
(i)
State one observation during the reaction.
Bubbles are formed
(ii)
Explain why the reaction rate decreases with time.
The concentration of hydrochloric acid decreases as it is
used up and lesser particles to collide with so lesser
reaction rate.
[3]
(d)
Describe how electrolysis can be used to purify copper.
12
[4]
Question 9
State the pH of a neutral solution.
-7
[1]
(b) Describe how a soluble salt can be prepared using an
acid and an insoluble base.
(a)
Warm the acid in a beaker and add the unsouble base in
the acid. Then pour excess remains so that the reaction is
fully reacted then filter the mixture to remove the excess
insoluble base then heat the filtrate by pouring into an
evaporating basin and place in a warm place then let it
crystallise to form salt
[4]
(c)
A student titrated sodium hydroxide with
hydrochloric acid.
Name a suitable indicator.
Universal indicator
(i)
State the colour change at the end-point.
red
[2]
(ii)
Explain why farmers add limestone to acidic soil.
Who knows?
(d)
[2]
13
Question 10
(a)
State two physical properties of metals.
1.High melting and boiling point
2. Good conductor of heat
[2]
(b)
Explain why aluminium is used to make aircraft bodies.
It has low density and doesn’t rust easily
[2]
Iron rusts in the presence of oxygen and water.
Describe one method used to prevent rusting and explain
how it works.
(c)
Painting, it blocks the oxygen from being in contact with iron
and blocks water from being in contact with iron so that it
doesn’t rust
[4]
Explain how sulfur dioxide causes acid rain.
[3]
14
Physics Section
Question 11
Define speed.
Speed is distance over time
[1]
A car travels 240 km in 3 hours.
Calculate the average speed.
The speed is 60km/h [2]
A cyclist accelerates uniformly from 4 m/s to 16
m/s in 6 s.
Calculate the acceleration.
Answer: 2m/s^2
[3]
Explain the difference between scalar and vector
quantities.
[2]
15
Question 12
(a)
State the principle of conservation of energy.
Engery canot be created or destroyed it can only be
transfered
[2]
(b)
A machine does 18 000 J of work in 30 s.
Calculate the
power output.
Answer: 60[2]
(c)
Explain why energy-efficient appliances reduce
electricity consumption.
Idk
[3]
(d)
A stone of mass 2.5 kg is lifted vertically by 12 m.
Calculate the gain in
16
gravitational potential
energy. (g = 10 N/kg)
Answer:300
[3]
Question 13
(a)
Describe how heat is transferred by conduction.
When one end of a material is heated the particles gain
kinetic energy and vibrate more. These particles collide with
each other particles and transfer energy from the hotter
region to the colder region
[2]
(b)
State two differences between evaporation and boiling.
1.Boiling has a fixed temperature
2. Evaporation happens at any temperature on the surface
[2]
17
Explain why dark, dull surfaces are good absorbers of
infrared radiation
They have a rough surface and dark color allowing more
energy to enter.
[2]
(c)
A wave has a frequency of 25 Hz and wavelength of 8
m.
Calculate the
wave speed
Answer:
200m/s[3]
(d)
Describe the difference between transverse and
longitudinal waves.
In traverse wave the wave is perpendicular to the dricten of
wave however in longitudinal wave the particle are parallel.
[3]
Question 14
18
Define electric current.
The electric charge flowling thourgh a circuit.
(a)
[1]
(b)
A resistor has a resistance of 12 Ω and a current of 2
A passes through it.
Calculate the potential
difference across the resistor
Answer:24v
[2]
(c)
State two safety features found in household electrical
wiring.
1.Fuse
2.Circuit breaker
[2]
(d)
Explain how an electromagnet works.
A soft iron surrounded in a copper coil wire creating a
magnective field so this becomes magnectised.
19
[3]
(e)
Describe the energy transfers in an electric motor.
Electrical energy is transferred into kinetic energy.
[2]
Question 15
A student investigates the cooling of hot water.
The student pours 200 cm3 of hot water into a beaker
and records the temperature every minute.
Time / Temperat
min
ure / °C
0
90
(a)
1
82
2
75
3
69
4
64
5
60
Plot a graph of
temperature against
20
time. [4]
(b)
Describe the trend shown by the graph.
As the time increase the temperature decreases.
[2]
(c)
Explain why the rate of cooling decreases with time.
As it is losing energy as time passes and it has nothing to
heat the water. Exothermix takes place as the energy is
being released into the surroundings decreases the
temperature of the water.
[3]
Suggest two improvements to increase the reliability of
the investigation.
1.Keep it is the same place
2.Maintain volume
[2]
(d)
The student repeats the investigation using a metal
beaker instead of a plastic beaker.
Predict and explain the effect on the cooling rate.
It will decrease but slower.
[4]
END OF QUESTION PAPER
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