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Question 1

(a) Fig. 1.1 is a diagram of the gas exchange system in humans. (Sub-topic – B11.1)

(i) Identify the parts labelled A, B and C in Fig. 1.1.

A: Trachea

B: Intercostal muscle

C: Diaphragm

▶️Answer/Explanation

Answer:
A: Trachea
B: Intercostal muscle
C: Diaphragm
Explanation: The trachea is the windpipe that carries air to the lungs. The intercostal muscles are located between the ribs and help in the expansion and contraction of the ribcage during breathing. The diaphragm is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity and plays a key role in breathing.

(ii) The alveoli are the gas exchange surface in humans.

State two features of alveoli that make them efficient gas exchange surfaces.

1. Large surface area

2. Thin walls

▶️Answer/Explanation

Answer:
any two from:
good blood supply ;
thin ;
large surface area ;
ventilated ;
AVP ;
(b) Two similar-sized groups of people are monitored. One group smokes tobacco (smokers) and the other group does not (non-smokers).

The number of smokers and non-smokers of different ages with chronic obstructive pulmonary disease (COPD) are recorded. Fig. 1.2 shows the results.

Describe the results shown in Fig. 1.2. (Sub-topic – B11.1)

▶️Answer/Explanation

Answer:
  any two from:
COPD increases with age ;
more smokers have COPD than non-smokers ;
more rapid increase of COPD with age in smokers ;
comparative data quote ;

(c) The tar in tobacco smoke stops the ciliated cells in the gas exchange system from working efficiently.

(i) Explain how this would increase the likelihood of infection in the lungs.

Include ideas about goblet cells in your answer. (Sub-topic – B11.1)

▶️Answer/Explanation

Answer:
goblet cells produce mucus ;
and any two from:
mucus traps, pathogens / particles / bacteria ;
cilia unable to remove, mucus / pathogens / bacteria ;
bacteria, reproduce / multiply (causing infection) ;

(ii) Name the substance in tobacco smoke that is addictive. (Sub-topic – B14.1)

▶️Answer/Explanation

Answer:
Nicotine
Explanation: Nicotine is the addictive substance in tobacco smoke. It stimulates the release of dopamine in the brain, creating a pleasurable sensation that leads to addiction.

Question 2

Ammonia, NH3, is made in the Haber process.

The balanced symbol equation is shown:

                N2 + 3H2 ⇌ 2NH3

Fig. 2.1 shows how ammonia is made.

(a) The reaction between nitrogen and hydrogen is a reversible reaction. State what is meant by a reversible reaction. (Sub-topic – C6.2)

▶️Answer/Explanation

Answer:

idea of a reaction that goes both ways ;

(b) Describe what happens to unreacted nitrogen and hydrogen. (Sub-topic – C6.2)

▶️Answer/Explanation

Answer:
recycled / owtte ;

(c) It is important to make ammonia as cheaply as possible. The conditions used to make ammonia are an iron catalyst, a high pressure, and a temperature of 450 °C.

Two of the factors that affect cost are:

  • the percentage of ammonia made
  • the rate of reaction

Explain why each condition is used.

Use ideas about the percentage of ammonia made and the rate of reaction. (Sub-topic – C6.2)

iron catalyst ………………………………………………………………………………………………………………

high pressure …………………………………………………………………………………………………………….

450°C ………………………………………………………………………………………………………………………

▶️Answer/Explanation

Answer:
Iron catalyst: Increases the rate of reaction by providing an alternative pathway with lower activation energy, making the process faster and more efficient.
High pressure: Increases the percentage of ammonia made because the reaction favors the side with fewer gas molecules (4 moles of gas on the left vs. 2 moles on the right).
450 °C: A compromise temperature that provides a reasonable rate of reaction while still allowing a significant yield of ammonia (lower temperatures favor higher yields but slow the reaction).
Explanation: The conditions are chosen to balance the rate of reaction and the yield of ammonia. The iron catalyst speeds up the reaction, high pressure increases the yield, and 450 °C is a compromise between rate and yield.

(d) The atoms in a molecule of nitrogen, N2, are held together by covalent bonds.

The electronic structure of nitrogen is 2,5.

Draw the dot-and-cross diagram to show the bonding in nitrogen.

You only need to include the outer shell electrons. (Sub-topic – C2.5)

▶️Answer/Explanation

Answer:

(e) Ammonia reacts with sulfuric acid.

The balanced symbol equation is shown:

             2NH3 + H2SO4 → (NH4)2SO4

Calculate the mass of sulfuric acid, H2SO4, needed to react completely with 68 g of ammonia. Show your working. (Sub-topic – C3.3)

[Ar : H, 1; N, 14; O, 16; S, 32]

                                                     mass of sulfuric acid = ……………………………………………… g

▶️Answer/Explanation

Answer:
Mass of sulfuric acid = 196 g
Explanation:

  1. Calculate the molar mass of NH3: 14 (N) + 3(1) (H) = 17 g/mol.
  2. Calculate the moles of NH3: 68 g ÷ 17 g/mol = 4 moles.
  3. From the balanced equation, 2 moles of NH3 react with 1 mole of H2SO4. Therefore, 4 moles of NH3 will react with 2 moles of H2SO4.
  4. Calculate the molar mass of H2SO4: 2(1) (H) + 32 (S) + 4(16) (O) = 98 g/mol.
  5. Calculate the mass of H2SO4: 2 moles × 98 g/mol = 196 g.

Question 3

(a) State the speed of electromagnetic waves in a vacuum. (Sub-topic – P3.3)

▶️Answer/Explanation

Answer: 3 × 108 m/ s ;

(b) Fig. 3.1 shows an incomplete electromagnetic spectrum. (Sub-topic – P3.3)

(i) Write visible light in its correct position in the spectrum.

▶️Answer/Explanation

Answer:

‘visible light’ placed in central box ;

(ii) State the form of electromagnetic radiation that has the highest frequency.

▶️Answer/Explanation

Answer:
Gamma rays have the highest frequency in the electromagnetic spectrum.
Explanation: Gamma rays have the shortest wavelengths and the highest frequencies in the electromagnetic spectrum. They are produced by nuclear reactions and radioactive decay.

(c) Visible light is an example of a transverse wave. (Sub-topic – P3.1)

(i) Use a double-headed arrow (\(\leftrightarrow\) or \(\uparrow\)) to label the wavelength of the transverse wave shown in Fig. 3.2.

▶️Answer/Explanation

Answer:
line drawn peak to peak / trough to trough / any identical points on adjacent waves ;

(ii) State the equation that links the frequency, speed, and wavelength of a wave.

▶️Answer/Explanation

Answer:

v = f λ ;

(d) Fig. 3.3 shows an object placed close to a thin converging lens. (Sub-topic – P3.2.3)

(i) Complete Fig. 3.3 to show how the rays of light from the object form an image.

▶️Answer/Explanation

Answer:
Draw two rays from the object:
1. A ray parallel to the principal axis that refracts through the focal point on the other side of the lens.
2. A ray passing through the center of the lens that continues straight without bending.
The image is formed where these two rays intersect.
Explanation: A converging lens focuses parallel rays to a point called the focal point. The image is formed at the intersection of the refracted rays.

(ii) The image formed by this lens is real. State what is meant by a real image.

▶️Answer/Explanation

Answer:
can be formed on a screen / is formed from real rays of light / formed from converging rays ;

(iii) Suggest a use for a thin converging lens such as the one shown in Fig. 3.3.

▶️Answer/Explanation

Answer:

magnifying glass ;

AVP ;

Question 4

(a) Antibiotics are drugs that are used to kill bacteria. A scientist investigates antibiotic resistance in bacteria.

The scientist uses four different antibiotic discs: A, B, C, and D.

The results are shown in Fig. 4.1.

The white areas show where no bacteria have grown.

The dark areas show where bacteria have grown. (Sub-topic – B14.1)

(i) Identify the antibiotic that is most effective against the bacteria.

▶️Answer/Explanation

Answer: D 

(ii) Identify the antibiotic that the bacteria are most resistant to.

▶️Answer/Explanation

Answer:
C

(b) The development of antibiotic resistance is an example of evolution by natural selection. (Sub-topic – B17.2)

(i) Complete the sentences to describe how strains of bacteria with antibiotic resistance develop.

A mutation occurs which causes a change in the ………………………………….. .

This mutation causes some bacteria to be resistant to antibiotics.

Antibiotics kill non-resistant bacteria.

Resistant bacteria survive and ………………………………….. .

The …………………………………… for resistance is passed on to their offspring.

Eventually, all the population of bacteria will be resistant to antibiotics.

▶️Answer/Explanation

Answer:
chromosome / gene ;
reproduce / AW ;
allele ;

(ii) Describe one way natural selection is different from artificial selection.

▶️Answer/Explanation

Answer:

traits / characteristics, are selected by humans (in artificial selection) / traits are selected by the environment in natural

selection ;
traits / characteristics, are usually chosen for economic reasons (in artificial selection) / traits are beneficial for survival in
natural selection ;
faster results (from artificial selection) / ORA ;
(artificial selection only) takes place in selected individuals / natural selection takes place in whole populations ;
(artificial selection) does not lead to evolution / ORA ;
(artificial selection) results in decreased (genetic) variation / diversity / ORA ;
(artificial selection) leads to increased likelihood of inherited / genetic disease ;
AVP ;

(c) Bacteria reproduce by a type of asexual reproduction. 

State one advantage and one disadvantage of asexual reproduction. (Sub-topic – B15.1)

advantage …………………………………………………………………………………………………………………

disadvantage …………………………………………………………………………………………………………….

▶️Answer/Explanation

Answer:
Advantage: 

no mates required / rapid / AVP ;
Disadvantage:   
no mates required / rapid / AVP ;

Question 5

Magnesium carbonate, MgCO3, reacts with dilute hydrochloric acid, HCl. Magnesium chloride, MgCl2, carbon dioxide, and water are made.

(a) Write the balanced symbol equation for this reaction. (Sub-topic – C3.1)

▶️Answer/Explanation

Answer:
MgCO3 + 2HCl → MgCl2 + CO2 + H2O
correct formulae ;
correct balancing ;

(b) A student investigates the reaction between magnesium carbonate and dilute hydrochloric acid. Fig. 5.1 shows the apparatus used.

(i) Look at the results for the dilute acid in Table 5.1. State how long it takes to make 33 cm3 of carbon dioxide gas. (Sub-topic – C6.2)

                                 time = ……………………. seconds

▶️Answer/Explanation

Answer:
 30 (seconds) ; 

(ii) Look at the results for both experiments in Table 5.1.

The total volume of carbon dioxide gas is the same at the end of both experiments.

Explain why. (Sub-topic – C6.2)

▶️Answer/Explanation

Answer:
(student used) same mass of magnesium carbonate;

(iii) Describe the test for carbon dioxide gas and its positive result. (Sub-topic – C12.5)

test ……………………………………………………………………………………………………………………
result ……………………………………………………………………………………………………………

▶️Answer/Explanation

Answer:
limewater ;
turns milky / cloudy ;

(iv) The volume of carbon dioxide gas made in both experiments is 48 cm3.

Calculate the mass of 48 cm3 of carbon dioxide gas.

The molar gas volume at 25°C is 24 dm3.

Show your working. (Sub-topic – C3.3)

[Ar : C, 12; O, 16]

                                     mass of carbon dioxide gas = ……………………………… g

▶️Answer/Explanation

Answer:

moles of CO2 = 48

÷ 24 000 or 0.048

÷ 24 or 0.0020 ;

Mr of CO2 = 44 ;
(mass of CO2 = 0.0020

× 44 =) 0.088 (g) ;

(c) Describe and explain the effect of increasing the concentration on the rate of reaction.

Explain your answer in terms of collisions between particles. (Sub-topic – C6.2)

▶️Answer/Explanation

Answer:
rate of reaction increases / owtte ;
particles are more crowded / more particles per unit volume / more particles per cm3 ;
more frequent collisions / more collisions per second ;

Question 6

Some students are investigating moments and turning effects. Fig. 6.1 shows a beam of uniform density in equilibrium. The beam has a mass of 20 g on one end and a stone on the other.

(a) State the meaning of the word equilibrium. (Sub-topic – P1.5.2)

▶️Answer/Explanation

Answer:
no resultant force and no resultant turning effect ;

(b) (i) Calculate the weight of the 20 g mass. Gravitational field strength \( g = 10 \, \text{N/kg} \). (Sub-topic – P1.3)

                                        weight = ………………………………. N

▶️Answer/Explanation

Answer:

0.02 or 20

× 10–3 (kg) ;
(W =) mg or 0.02
× 10 ;

0.2 (N) ;

(ii) Calculate the mass of the stone. State the unit for your answer. (Sub-topic – P1.5.2)

                                        mass = ……………… unit ………………

▶️Answer/Explanation

Answer:

clockwise moment = force

× distance or 0.2

× 0.25 or 0.05 ;

anti-clockwise moment = clockwise moment ;
F = 0.05
÷ 0.19 or 0.263 /
m = 0.263 ÷ 10 or 0.026 (kg) or 26 (g) ;
g / kg ;

(c) Describe a method for determining the volume of an irregular object like the stone. (Sub-topic – P1.4)

▶️Answer/Explanation

Answer:
immerse in water ;
measure volume of displaced water ;

Question 7

(a) Fig. 7.1 is a diagram of a villus. (Sub-topic – B7.2)

(i) Table 7.1 shows some of the names, functions, and letters in Fig. 7.1 of parts of a villus. Complete Table 7.1.

▶️Answer/Explanation

Answer:

NameLetter in Fig. 7.1Function
LactealXAbsorption of fats
Epithelial cellYContain microvilli
CapillaryZTransport of nutrients around the body
(ii) Describe how villi aid the process of digestion.
▶️Answer/Explanation

Answer:
increases surface area ;
for more absorption ;

(b) Fig. 7.2 is a diagram of the alimentary canal and associated organs. (Sub-topic – B7.2)

(i) Identify the letter on Fig. 7.2 that represents:

  • where egestion occurs ……………………………………….
  • where bile is produced ……………………………………….
  • where dental decay can occur ……………………………
▶️Answer/Explanation

Answer:

  •  F : 
  • H :
  • A :

(ii) State the name of the type of organism that causes dental decay.

▶️Answer/Explanation

Answer:
Bacteria

(c) Bile is mixed with gastric juice when they enter the small intestine.

Describe the effect of bile on the pH of the gastric juice. (Sub-topic – B7.3)

▶️Answer/Explanation

Answer:
increases ;

Question 8

Fig. 8.1 shows the apparatus that is used to electrolyse concentrated aqueous sodium chloride.

(a) (i) Hydrogen gas is made at the negative electrode. State the name of the negative electrode. (Sub-topic – C4.1)

▶️Answer/Explanation

Answer:
 cathode :

(ii) State the name of the pale green gas X, formed at the positive electrode. (Sub-topic – C4.1)

▶️Answer/Explanation

Answer:
 chlorine :

(iii) During the electrolysis, sodium hydroxide solution forms in the apparatus.

Sodium hydroxide solution is an alkali.

Describe a simple test and its positive result to show that sodium hydroxide is an alkali. (Sub-topic – C7.1)

test ……………………………………………………………………………………………………………….
result ……………………………………………………………………………………………………………

▶️Answer/Explanation

Answer:
Test:

universal indicator / (red) litmus / pH meter ;
result:
universal indicator would turn blue or purple / pH greater than 7 /
red litmus turns blue / pH meter or pH probe gives pH greater than 7 ;

(b) Construct the ionic half-equation for the formation of hydrogen gas, H2, at the negative electrode.

Use e– to represent an electron. (Sub-topic – C4.1)

▶️Answer/Explanation

Answer:
2H+ + 2e– → H2
correct formulae ;
correct balancing ;

(c) Hydrogen gas, H2, has a boiling point of –253°C.

Sodium chloride, NaCl, has a boiling point of 1465°C.

Explain the difference in these boiling points in terms of attractive forces. (Sub-topic – C2.4)

▶️Answer/Explanation

Answer:
sodium chloride has strong (attractive) forces between (oppositely charged sodium ions and chloride) ions ;
hydrogen has weak intermolecular forces / weak (attractive) forces between molecules ;
strong (electrostatic) attractive forces take more energy to overcome than weak (intermolecular) forces / ORA ;

Question 9

Fig. 9.1 shows a person sitting in an inflatable raft.

(a) The raft consists of a large rubber tube inflated with air. (Sub-topic – P1.5.1)

(i) Describe how the motion of the air molecules causes pressure inside the rubber tube.

(ii) As the sun warms up the air inside the rubber tube, the pressure increases.

Explain why the pressure increases.

▶️Answer/Explanation

(i) collisions of molecules with walls / raft ;

produces a force ;

(ii) molecules move faster / have more (kinetic) energy ;
molecules collide more often / more frequently with walls ;
larger force exerted on walls ;

(b) The combined weight of the raft and the person is 1100 N. The raft exerts a pressure of 500 Pa on the surface of the water. ( Sub-topic – P1.6.1)

(i) Calculate the area of raft in contact with the water.

                                                  area = ……………………………. m2

(ii) The tide causes the raft to move at a speed of 4.0 m/s. Calculate the kinetic energy of the raft and the person. (gravitational field strength \( g = 10 \, \text{N/kg} \))

                                                   kinetic energy = ………………………………. J

(iii) State what causes tides.

▶️Answer/Explanation

(i) (A =) F÷ P or 1100÷ 500 ;
2.2 (m2) ;

(ii) (mass =) 110 kg ;
(KE =) 1⁄2 mv2 or 1⁄2
× 110
× 42 ;

880 (J) ;

(iii) the moon ;

Question 10

Hormones control blood glucose concentration. (Sub-topic – B13.2)

(a) State the name of the part of the blood that transports hormones.

▶️Answer/Explanation

plasma.

(b) Fig. 10.1 is a flowchart showing the control of blood glucose concentration. Complete the flowchart in Fig. 10.1.

▶️Answer/Explanation

pancreas in boxes 2 and 6 ;
insulin in box 3 ;
glycogen in box 4 and 8 ;
liver in box 8 ;

(c) State the term that is used to describe this type of control.

▶️Answer/Explanation

negative feedback:

(d) Name one other hormone that increases the glucose concentration of the blood.

▶️Answer/Explanation

adrenaline :

(e) Table 10.1 compares nervous and hormonal control. Complete Table 10.1.

 Hormonal ControlNervous Control
Transmission methodIn the blood 
Speed of transmission  
Length of effect  
▶️Answer/Explanation

The completed table is as follows:

 Hormonal ControlNervous Control
Transmission methodIn the bloodBy neurones / electrical impulses
Speed of transmissionSlowFast
Length of effectLong-lastingShort-lived

Question 11

Sub-topic – C2.2

This is the information given on the Periodic Table about an atom of iron.

                                   

(a) Complete Table 11.1 to show the numbers of protons and neutrons in this iron atom.

ParticleNumber
Protons 
Neutrons 
Electrons26
▶️Answer/Explanation

The completed table is as follows:

ParticleNumber
Protons26
Neutrons30
Electrons26

 

(b) Iron metal corrodes. Stainless steel is an alloy made from iron and chromium.

Describe one difference in the properties of the alloy stainless steel and the metal iron.

▶️Answer/Explanation

stainless steel is more resistant to corrosion : 

(c) Iron pyrites is an ionic compound.

Fig. 11.1 shows a structure for iron pyrites.

Determine the formula of iron pyrites using Fig. 11.1.

▶️Answer/Explanation

FeS2 :

(d) Iron metal reacts with the non-metal oxygen to form iron oxide.

Iron oxide is an ionic compound.

Describe how metallic and non-metallic elements form ionic bonds.

▶️Answer/Explanation

Ionic bonds are formed when:

  • Metallic atoms lose electrons to form positively charged ions (cations).
  • Non-metallic atoms gain electrons to form negatively charged ions (anions).
  • The oppositely charged ions are held together by strong electrostatic forces of attraction.

For example, in iron oxide, iron (Fe) loses electrons to form Fe2+ or Fe3+, and oxygen (O) gains electrons to form O2-.

(e) Iron is extracted from iron oxide by reduction with carbon.

Explain why carbon can be used to extract iron from iron oxide.

▶️Answer/Explanation

Carbon can be used to extract iron from iron oxide because:

  • Carbon is more reactive than iron, so it can displace iron from its oxide.
  • Carbon reacts with iron oxide in a redox reaction, where carbon acts as the reducing agent.
  • The reaction is: \[ \text{Fe}_2\text{O}_3 + 3\text{C} \rightarrow 2\text{Fe} + 3\text{CO} \]

Question 12

Sub-topic – P4.5.6

Fig. 12.1 shows a transformer.

(a) (i) State the name of the component labelled X.

(ii) Suggest a suitable material for making component X.

▶️Answer/Explanation

(i)  core :

(ii)  soft iron :

(b) There are 5 turns on the primary coil and 30 on the secondary coil.

(i) Calculate the reading on the voltmeter.

                                          voltage = ……………………………….V

(ii) Suggest two ways to increase the reading on the voltmeter.

▶️Answer/Explanation

(i) The voltage on the secondary coil can be calculated using the transformer equation: \[ \frac{V_s}{V_p} = \frac{N_s}{N_p} \] Where:

  • \( V_p = 10 \, \text{V} \) (primary voltage)
  • \( N_p = 5 \) (primary turns)
  • \( N_s = 30 \) (secondary turns)

Rearranging the equation: \[ V_s = V_p \times \frac{N_s}{N_p} = 10 \times \frac{30}{5} = 60 \, \text{V} \] The reading on the voltmeter is 60 V.

(ii) Two ways to increase the reading on the voltmeter are:

  1. Increase the number of turns on the secondary coil (\( N_s \)).
  2. Decrease the number of turns on the primary coil (\( N_p \)).

(c) The following statements explain how the transformer produces a reading on the voltmeter. The statements are in the wrong order.

A. An alternating potential difference is applied to the primary coil.
B. The secondary coil experiences a changing magnetic field.
C. This produces a changing magnetic field in the primary coil.
D. An alternating current flows in the primary coil.
E. This produces an alternating potential difference across the voltmeter.

Arrange the statements into the correct order. The first and last steps have been done for you.

▶️Answer/Explanation

The correct order of the statements is:

  1. A
  2. D
  3. C
  4. B
  5. E

Explanation:

  1. An alternating potential difference is applied to the primary coil.
  2. An alternating current flows in the primary coil.
  3. This produces a changing magnetic field in the primary coil.
  4. The secondary coil experiences a changing magnetic field.
  5. This produces an alternating potential difference across the voltmeter.

(d) The transformer has an efficiency of 95%.

Describe what is meant by an efficiency of 95%.

▶️Answer/Explanation

An efficiency of 95% means that 95% of the input power is transferred to the output, and the remaining 5% is lost as heat or other forms of energy.

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