Question 1
Enzymes have an important role in the process of digestion.
(a) Define the term enzyme.
▶️Answer/Explanation
Enzymes are proteins that act as biological catalysts, speeding up chemical reactions in living organisms without being consumed in the process.
(b) Fig. 1.1 shows the effect of pH on two different enzymes. (Sub-topic – B5.1)
(i) State the pH at which enzyme B is most active in Fig. 1.1.
▶️Answer/Explanation
Enzyme B is most active at pH 7.5.
(ii) Explain the results for enzyme B at pH 10 in Fig. 1.1.
▶️Answer/Explanation
At pH 10, enzyme B is denatured. This means that the enzyme’s active site has changed shape, preventing the substrate from fitting into it. As a result, no products are released, and the enzyme cannot catalyze the reaction.
(iii) State where in the alimentary canal enzyme A is most likely to be found.
▶️Answer/Explanation
Enzyme A is most likely to be found in the stomach.
(iv) Suggest the name of enzyme A.
▶️Answer/Explanation
Enzyme A is likely to be protease.
(c) Once food is digested, nutrients are absorbed across the villi walls. (Sub-topic – B7.2)
(i) State where villi are found in the alimentary canal.
▶️Answer/Explanation
Villi are found in the small intestine.
(ii) State the function of the lacteal in the villi.
▶️Answer/Explanation
The lacteal in the villi is responsible for the absorption of fats.
Question 2
Carbon monoxide is a common pollutant in the air. (Sub-topic – C10.2)
Many countries have rules to limit the maximum percentage of carbon monoxide in exhaust gases
produced by car engines.
Table 2.1 shows how the maximum allowed percentage (%) of carbon monoxide in car exhaust
gases has changed in the United Kingdom.
(a) Suggest one reason why the maximum allowed percentage (%) of carbon monoxide in car exhaust gases has decreased since 1985.
▶️Answer/Explanation
One reason for the decrease in the maximum allowed percentage of carbon monoxide in car exhaust gases since 1985 is the increased public awareness and concern about the toxic and harmful effects of carbon monoxide on human health and the environment.
(b) Describe and explain how carbon monoxide is produced when petrol is burned in a car engine.
▶️Answer/Explanation
Carbon monoxide is produced during the incomplete combustion of petrol in a car engine. This occurs when there is insufficient oxygen available for the complete combustion of the fuel, leading to the formation of carbon monoxide instead of carbon dioxide.
(c) Catalytic converters are fitted to car exhausts to reduce the volume of pollutants released into the air.
Complete the symbol equation to show how a catalytic converter removes carbon monoxide gas.
▶️Answer/Explanation
2CO + O2 → 2CO2
(d) Catalytic converters remove oxides of nitrogen as well as carbon monoxide from exhaust gases.
State two other effects of air pollution which are reduced by using catalytic converters.
▶️Answer/Explanation
1. Reduction in the formation of acid rain, which is caused by sulfur dioxide and nitrogen oxides reacting with water vapor in the atmosphere.
2. Reduction in respiratory problems and other health issues caused by inhaling pollutants such as nitrogen oxides and particulate matter.
(e) The catalyst in a catalytic converter is made from metal.
State where in the Periodic Table this metal is most likely to be found.
Choose from the list.
group I elements
group VII elements
group 0 elements
transition elements
▶️Answer/Explanation
The catalyst in a catalytic converter is most likely to be found in the transition elements of the Periodic Table.
Question 3
(a) Fig. 3.1 shows four electrical component names and their symbols. (Sub-topic – P4.3.1)
Draw lines to match each component name with its symbol.
One line has been drawn as an example.
▶️Answer/Explanation
Fixed resistor: 
Light dependent resistor: 
Thermistor: 
Variable resistor: 
(b) A student investigates how the resistance of a thermistor changes with temperature. (Sub-topic – P4.2.4)
Fig. 3.2 shows the results of this investigation.
(i) Using Fig. 3.2, state the temperature when the resistance of the thermistor is 5 kΩ.
temperature = ……………………………………………..°C
▶️Answer/Explanation
The temperature when the resistance of the thermistor is 5 kΩ is 32°C.
(ii) Calculate the total resistance of two identical thermistors placed in series when the resistance of each thermistor is 5 kΩ.
total resistance = ……………………………………………. kΩ
▶️Answer/Explanation
The total resistance of two identical thermistors placed in series is 10 kΩ.
(iii) Calculate the total resistance of two identical thermistors placed in parallel when the resistance of each thermistor is 5 kΩ.
total resistance = …………………………………………… kΩ
▶️Answer/Explanation
The total resistance of two identical thermistors placed in parallel is 2.5 kΩ.
(c) A fixed resistor has a current of 3.4A passing through it. (Sub-topic – P4.2.2)
Calculate the charge passing through the fixed resistor during 25 seconds. State the unit of your answer.
total resistance = …………………………………………… kΩ
▶️Answer/Explanation
The charge passing through the fixed resistor is 85 C (Coulombs).
Question 4
(a) A student investigates the effect of light intensity on the rate of photosynthesis at two different temperatures. (Sub-topic – B6.1)
(i) Compare the effect of light intensity on the rate of photosynthesis at the two different temperatures seen in Fig. 4.1.
▶️Answer/Explanation
At both temperatures, the rate of photosynthesis increases with increasing light intensity until it reaches a plateau. However, the rate of photosynthesis reaches its maximum at a lower light intensity at 5°C compared to 40°C. At 40°C, the rate of photosynthesis continues to increase with light intensity for a longer range before plateauing.
(ii) State the factor limiting the rate of photosynthesis at point X in Fig. 4.1.
▶️Answer/Explanation
At point X, the factor limiting the rate of photosynthesis is light intensity.
(iii) Complete the sentences to explain why light is necessary for photosynthesis.
▶️Answer/Explanation
The light energy is absorbed by a chemical in the leaf called chlorophyll.
This chemical then transfers the light energy to chemical energy in molecules.
The energy is used to synthesise carbohydrates.
(b) State the word equation for photosynthesis.
▶️Answer/Explanation
Carbon dioxide + water → glucose + oxygen
(c) Name the cells in a leaf where most photosynthesis occurs.
▶️Answer/Explanation
The cells in a leaf where most photosynthesis occurs are the palisade mesophyll cells.
Question 5
Large hydrocarbon molecules can be cracked to make smaller molecules. (Sub-topic – C11.5)
The equation represents the cracking of hydrocarbon, C20H42.
C20H42 → C6H14 + 2C5H10 + 2C2H4
(a) State the formula of the product of the reaction which is an alkane.
▶️Answer/Explanation
The formula of the product which is an alkane is C6H14.
(b) Table 5.1 shows the boiling point, flammability and viscosity of C20H42 compared with the properties of C6H14, C5H10 and C2H4.
State which letter, A, B, C or D, shows how the properties of C20H42 compare with the properties of C6H14, C5H10 and C2H4.
▶️Answer/Explanation
The letter that shows how the properties of C20H42 compare with the properties of C6H14, C5H10 and C2H4 is D.
(c) The hydrocarbon C2H4 is burnt in air. Complete combustion occurs.
Write the balanced symbol equation for this reaction.
▶️Answer/Explanation
C2H4 + 3O2 → 2CO2 + 2H2O
(d) Nylon is a polymer produced when monomers join together and release a small molecule.
State the name of the small molecule released.
▶️Answer/Explanation
The small molecule released is water.
(e) Poly(propene) is a polymer made from the monomer propene.
Complete the equation to show the structure of poly(propene).
▶️Answer/Explanation
n CH3CH=CH2 → [CH3CH-CH2]n
(f) Propene, C3H6, reacts with aqueous bromine.
(i) Describe what is seen when propene reacts with aqueous bromine.
▶️Answer/Explanation
When propene reacts with aqueous bromine, the orange-brown color of the bromine solution is decolorized, turning colorless.
(ii) Fig. 5.1 shows the energy level diagram for the reaction of propene with aqueous bromine.
Complete the energy level diagram in Fig. 5.1. Include labelled arrows to show:
- the energy given out
- the activation energy.
▶️Answer/Explanation
In the energy level diagram, the reactants (C3H6 + Br2) are at a higher energy level than the products (C3H6Br2). The activation energy is the energy required to reach the transition state from the reactants. The energy given out is the difference in energy between the reactants and the products.
Question 6
Fig. 6.1 shows a rollercoaster ride at a theme park. The rollercoaster travels on a frictionless track. (Sub-topic – P1.2)
(a) Use a letter from A to E to state the position at which the rollercoaster car has:
• the least gravitational potential energy ………………………………
• less kinetic energy than it does at position E ………………………………
• the most kinetic energy. ………………………………
▶️Answer/Explanation
- the least gravitational potential energy: D
- less kinetic energy than it does at position E: A
- the most kinetic energy: D
(b) The rollercoaster car has a mass of 750 kg. At position C the rollercoaster car is 36 m above the ground level and is moving at 20 m/s.
(i) Calculate the gravitational potential energy lost by the rollercoaster car as it travels from C to the ground level.
gravitational field strength g = 10N/ kg
gravitational potential energy = ………………………………………………. J
▶️Answer/Explanation
Gravitational potential energy lost = mgh = 750 kg × 10 N/kg × 36 m = 270,000 J
(ii) Calculate the kinetic energy of the rollercoaster car at C.
kinetic energy = ………………………………………………. J
▶️Answer/Explanation
Kinetic energy = ½ mv² = ½ × 750 kg × (20 m/s)² = 150,000 J
(iii) State the change in the total energy of the rollercoaster car as it travels on the frictionless track from C to ground level.
change in total energy = ………………………………………………. J
▶️Answer/Explanation
The change in the total energy of the rollercoaster car is 0 J, as energy is conserved in a frictionless system.
(c) Fig. 6.2 shows a speed-time graph for the rollercoaster car’s journey between positions D and E.
(i) Use Fig. 6.2 to determine the change in speed of the rollercoaster car between t = 2s and t = 4s.
change in speed = …………………………………………. m/s
▶️Answer/Explanation
The change in speed of the rollercoaster car between t = 2s and t = 4s is -22 m/s.
(ii) Calculate the acceleration of the rollercoaster car between t = 2s and t = 4s.
acceleration = ………………………………………… m/ s2
▶️Answer/Explanation
Acceleration = Δv / Δt = -22 m/s / 2 s = -11 m/s²
(iii) Use Fig. 6.2 to describe the motion of the rollercoaster car between t = 0s and t = 5s.
▶️Answer/Explanation
Between t = 0s and t = 5s, the rollercoaster car is decelerating (slowing down) with non-constant deceleration at the start (before 2s) and constant deceleration at the end (after 2s).
Question 7
(a) Fig. 7.1 is a diagram of a human eye. (Sub-topic – B13.1)
(i) Table 7.1 shows some of the letters, the names and functions of the parts in Fig. 7.1.
Complete Table 7.1.
| Name of Part | Letter in Fig. 7.1 | Function |
|---|---|---|
| Adjusts the amount of light entering the eye | ||
| G | ||
| Retina | ||
| D | Refracts light entering the eye |
▶️Answer/Explanation
| Name of Part | Letter in Fig. 7.1 | Function |
|---|---|---|
| Iris | C | Adjusts the amount of light entering the eye |
| Optic Nerve | G | Transfers impulses to the brain |
| Retina | A | Contains light receptors / Detects light |
| Cornea | D | Refracts light entering the eye |
(ii) State the letters in Fig. 7.1 of the two parts of the eye responsible for changing the shape of the lens during accommodation.
▶️Answer/Explanation
The letters are E and F.
(iii) Name the two muscles in the iris responsible for the pupil reflex.
▶️Answer/Explanation
The two muscles are the circular and radial muscles.
(b) The pupil reflex is an involuntary action.
Place ticks (✓) in the boxes to show two voluntary actions.
| Action | Voluntary |
|---|---|
| Blinking when dust gets in your eye | |
| Eating a burger | |
| Reading a book | |
| Removing your hand from a very hot object | |
| Sweating when you get hot |
▶️Answer/Explanation
| Action | Voluntary |
|---|---|
| Blinking when dust gets in your eye | |
| Eating a burger | ✓ |
| Reading a book | ✓ |
| Removing your hand from a very hot object | |
| Sweating when you get hot |
Question 8
A scientist investigates the electrolysis of lead(II) bromide. (Sub-topic – C4.1)
(a) Explain why electrolysis will not take place using the apparatus shown in Fig. 8.1.
▶️Answer/Explanation
Electrolysis will not take place because lead(II) bromide is in its solid state. For electrolysis to occur, the ionic compound must be molten or in solution so that the ions are free to move and conduct electricity.
(b) The electrodes are made of graphite.
Explain why graphite conducts electricity. Use ideas about the structure and bonding in graphite.
▶️Answer/Explanation
Graphite conducts electricity because it has delocalized electrons. In graphite, each carbon atom is bonded to three others, forming layers of hexagonal rings. The fourth electron from each carbon atom is delocalized and free to move between the layers, allowing graphite to conduct electricity.
(c) Another scientist investigates the electrolysis of concentrated aqueous sodium chloride.
Fig. 8.2 shows the apparatus the scientist uses.
(i) Describe the test for chlorine gas and its positive result.
test …………………………………………………………………………………………
result ……………………………………………………………………………………..
▶️Answer/Explanation
The test for chlorine gas involves using damp litmus paper. If chlorine gas is present, the litmus paper will be bleached (turned white).
(ii) The scientist collects 3.3 cm³ of chlorine gas, Cl₂, in the electrolysis experiment.
Calculate the mass of chlorine gas collected. The molar gas volume at 25°C is 24 dm³. Show your working.
▶️Answer/Explanation
First, convert 3.3 cm³ to dm³: 3.3 cm³ = 0.0033 dm³
Moles of Cl₂ = Volume / Molar gas volume = 0.0033 dm³ / 24 dm³ = 0.0001375 mol
Molar mass of Cl₂ = 2 × 35.5 = 71 g/mol
Mass of Cl₂ = Moles × Molar mass = 0.0001375 mol × 71 g/mol = 0.00976 g
Question 9
Fig. 9.1 shows a helium-filled balloon attached to a spring. The spring is attached to a table top to stop the balloon moving upwards. The balloon is in equilibrium. (Sub-topic – P1.5.1)
(a) The helium-filled balloon has a mass of 6.5 g.
(i) Calculate the weight of the helium-filled balloon. gravitational field strength g = 10N/ kg
weight = …………………………………………….. N
▶️Answer/Explanation
Weight = mass × gravitational field strength = 0.0065 kg × 10 N/kg = 0.065 N
(ii) The balloon causes the spring to extend by 0.50 cm. The spring constant of the spring is 0.45 N/cm.
Calculate the force on the spring.
force = …………………………………………….. N
▶️Answer/Explanation
Force = spring constant × extension = 0.45 N/cm × 0.50 cm = 0.225 N
(iii) State the total downwards force acting on the balloon.
force = …………………………………………….. N
▶️Answer/Explanation
The total downwards force acting on the balloon is 0.29 N (weight of the balloon + force due to the spring).
(b) A student places the balloon under an infrared lamp to warm the helium gas.
(i) Suggest the colour of balloon which will give the greatest rate of increase in gas temperature.
Explain your answer.
colour ……………………………………………….
explanation
▶️Answer/Explanation
The colour of the balloon that will give the greatest rate of increase in gas temperature is black. Black surfaces are good absorbers of infrared radiation, which will increase the temperature of the gas inside the balloon more quickly.
(ii) Explain why the size of the balloon increases as it is heated.
▶️Answer/Explanation
As the balloon is heated, the helium gas inside gains kinetic energy, causing the gas molecules to move faster and collide more frequently with the walls of the balloon. This increases the pressure inside the balloon, causing it to expand.
Question 10
(a) Table 10.1 shows the daily energy requirements of different females. (Sub-topic – B7.1)
| Type of person | Daily energy requirements/kJ |
| 30 – year – old female | 7 800 |
| 30-year-old breast-feeding female | 9 100 |
| 30-year-old pregnant female | 10 200 |
(i) Calculate the difference in daily energy requirement between a 30-year-old female and a 30-year-old breast-feeding female in Table 10.1.
……………………………………………………………………………………………………………….. kJ
▶️Answer/Explanation
Difference = 9,100 kJ – 7,800 kJ = 1,300 kJ
(ii) Explain why there is a difference in daily energy requirement of a 30-year-old female and a 30-year-old pregnant female in Table 10.1.
▶️Answer/Explanation
A pregnant female requires more energy to support the growth and development of the fetus, as well as to maintain her own body functions. This increased energy demand is reflected in the higher daily energy requirement.
(b) State one food group which is a good source of vitamin C.
▶️Answer/Explanation
One food group that is a good source of vitamin C is fruits.
(c) Vitamins and minerals are important components of a balanced diet.
Name three other components of a balanced diet.
▶️Answer/Explanation
1. Carbohydrates
2. Proteins
3. Fats
(d) Dissolved nutrients cross the placenta from mother to fetus.
The boxes on the left show some parts of a pregnant female’s body.
The boxes on the right show the functions of these parts.
Draw lines to link each part with its function
▶️Answer/Explanation
| Part | Function |
|---|---|
| Amniotic fluid | Protects the fetus from mechanical damage |
| Placenta | Acts as a barrier against toxins |
| Umbilical cord | Transfers materials between fetus and the placenta |
| Uterus | Where the fetus develops |
(e) State the name of the excretory gas that would pass from fetus to the mother.
▶️Answer/Explanation
The excretory gas that would pass from the fetus to the mother is carbon dioxide.
Question 11
(a) An oxygen atom has the electronic structure 2,6.
Use the electronic structure to explain which group of the Periodic Table oxygen is in.
▶️Answer/Explanation
Answer: Oxygen is in Group VI (Group 6) of the Periodic Table because it has 6 electrons in its outer shell.
(b) Sodium forms an ionic compound with oxygen.
State the formulae of a sodium ion and an oxide ion.
Use the formulae of the ions to determine the formula of the ionic compound sodium oxide.
formula of a sodium ion ……………………………………………………………………………………………….
formula of an oxide ion ………………………………………………………………………………………………..
formula of sodium oxide ………………………………………………………………………………………………
▶️Answer/Explanation
Answer:
- Formula of a sodium ion: Na+
- Formula of an oxide ion: O2-
- Formula of sodium oxide: Na2O
Explanation: Sodium (Na) loses one electron to form a Na+ ion, while oxygen (O) gains two electrons to form an O2- ion. To balance the charges, two sodium ions are needed for every oxide ion, resulting in the formula Na2O.
(c) Oxygen can also form covalent bonds.
Complete the dot-and-cross diagram to show the covalent bonding in a molecule of carbon dioxide.
You only need to include the outer shell electrons.
▶️Answer/Explanation
Answer:
In a carbon dioxide (CO2) molecule, carbon forms double covalent bonds with each oxygen atom. The dot-and-cross diagram shows:
- Carbon shares two electrons with each oxygen atom.
- Each oxygen atom shares two electrons with carbon.
Explanation: Carbon has 4 valence electrons, and each oxygen has 6. Carbon shares two electrons with each oxygen, forming two double bonds, resulting in a stable CO2 molecule.
(d) Covalent compounds, such as carbon dioxide, have low melting points. State which letter, A, B, C or D, in Table 11.1 gives the correct explanation for why most covalent compounds have low melting points.
▶️Answer/Explanation
Answer: D (weak intermolecular forces of attraction) Explanation: Covalent compounds have low melting points because the intermolecular forces between the molecules are weak. These weak forces require less energy to overcome, resulting in lower melting points.
(e) Calculate the relative molecular mass, Mr , of aluminium sulfate, Al2SO4.
Show your working.
[Ar: Al, 27; O, 16; S, 32]
relative molecular mass = …………………………………………………
▶️Answer/Explanation
Answer:
Relative molecular mass of \( Al_2(SO_4)_3 \):
- Aluminium (Al): 2 × 27 = 54
- Sulfur (S): 3 × 32 = 96
- Oxygen (O): 12 × 16 = 192
Total \( M_r \) = 54 + 96 + 192 = 342
Explanation: The relative molecular mass is calculated by summing the atomic masses of all the atoms in the molecule. For \( Al_2(SO_4)_3 \), there are 2 aluminium atoms, 3 sulfur atoms, and 12 oxygen atoms.
Question 12
(a)(i) State the speed of visible light in a vacuum.
▶️Answer/Explanation
Answer: The speed of visible light in a vacuum is \( 3 \times 10^8 \, \text{m/s} \).
(ii) Red light has a wavelength of \( 7.1 \times 10^{-7} \, \text{m} \). Use your answer to (a)(i) to calculate the frequency of red light.
▶️Answer/Explanation
Answer:
Frequency (\( f \)) = \( \frac{v}{\lambda} \)
Where \( v = 3 \times 10^8 \, \text{m/s} \) and \( \lambda = 7.1 \times 10^{-7} \, \text{m} \).
\( f = \frac{3 \times 10^8}{7.1 \times 10^{-7}} = 4.23 \times 10^{14} \, \text{Hz} \).
Explanation: The frequency of light is calculated using the formula \( f = \frac{v}{\lambda} \), where \( v \) is the speed of light and \( \lambda \) is the wavelength.
(b) A laser is a device which emits a ray of light.
Fig. 12.1 shows a beam of red light from a laser passing through a rectangular glass block.
(i) Name the process shown in Fig. 12.1.
▶️Answer/Explanation
Answer: The process shown is refraction. Explanation: Refraction occurs when light passes from one medium (e.g., air) into another (e.g., glass), causing the light to change direction due to the change in speed.
(ii) Describe what causes the process shown in Fig. 12.1.
▶️Answer/Explanation
Answer:
The process of refraction is caused by the change in speed of light as it passes from one medium to another. When light enters a denser medium (e.g., glass), it slows down, causing the light to bend towards the normal. When it exits the denser medium, it speeds up and bends away from the normal.
Explanation: The bending of light is due to the change in the refractive index of the two media, which affects the speed of light.
(c) The laser used in Fig. 12.1 has a useful power output of 1200 W and is 80% efficient. Calculate the power input of the laser.
power input = …………………………………………….. W
▶️Answer/Explanation
Answer:
Efficiency (\( \eta \)) = \( \frac{\text{Useful Power Output}}{\text{Power Input}} \times 100 \).
Given \( \eta = 80\% \) and Useful Power Output = 1200 W,
\( 80 = \frac{1200}{\text{Power Input}} \times 100 \).
Power Input = \( \frac{1200 \times 100}{80} = 1500 \, \text{W} \).
Explanation: The power input is calculated by rearranging the efficiency formula to solve for the input power.