Question 1(a) (Subtopic – B2.1)
Fig. 1.1 is a diagram of a single-celled organism called a euglena.
(i) Table 1.1 shows some of the cell components of animal, euglena and plant cells. Complete Table 1.1 by placing ticks (✓) to show the correct cell components of each type of cell.
Use the information in Fig. 1.1 and your knowledge to answer the question.
| Type of cell | Cell wall | Chloroplast | Nucleus | Vacuole |
|---|---|---|---|---|
| Animal | ✓ | |||
| Euglena | ✓ | ✓ | ||
| Plant | ✓ | ✓ | ✓ | ✓ |
(ii) State evidence from Fig. 1.1 for and against euglena being a plant cell.
Evidence for: Euglena has chloroplasts, which are typically found in plant cells.
Evidence against: Euglena does not have a cell wall or a large central vacuole, which are characteristic of plant cells.
▶️Answer/Explanation
Answer:
(i) The completed table is shown above.
(ii) Evidence for: Euglena has chloroplasts, which are typically found in plant cells.
Evidence against: Euglena does not have a cell wall or a large central vacuole, which are characteristic of plant cells.
Question 1(b) (Subtopic – B2.1)
State the function of the nucleus.
The nucleus controls the cell’s activities and contains genetic material (DNA).
▶️Answer/Explanation
Answer: The nucleus controls the cell’s activities and contains genetic material (DNA).
Question 1(c)(Subtopic – B2.2)
The length of a palisade cell is 0.08 mm. The length of a red blood cell is 0.007 mm. Calculate how many times bigger a palisade cell is than a red blood cell. Give your answer to the nearest whole number.
To calculate how many times bigger the palisade cell is compared to the red blood cell, divide the length of the palisade cell by the length of the red blood cell:
\[ \text{Number of times bigger} = \frac{0.08 \, \text{mm}}{0.007 \, \text{mm}} \approx 11.428 \]
Rounding to the nearest whole number, the palisade cell is approximately 11 times bigger than the red blood cell.
▶️Answer/Explanation
Answer: 0.08÷ 0.007 or 11.428 ;
11 ;
Question 1(d)(Subtopic – B2.6 )
Fig. 1.2 shows a type of nerve cell (neurone)
(i) Name the type of neurone shown in Fig. 1.2.
The type of neurone shown is a sensory neurone.
(ii) The type of neurone shown in Fig. 1.2 can be 1.5 m in length. Suggest why these cells need to be very long.
These cells need to be very long to transmit impulses over large distances, such as from the extremities of the body to the central nervous system.
▶️Answer/Explanation
Answer:
(i) The type of neurone shown is a sensory neurone.
(ii) These cells need to be very long to transmit impulses over large distances, such as from the extremities of the body to the central nervous system.
Question 2(a) (Subtopic – C8.2)
2(a) Table 2.1 shows the melting points and reactivity with water of three Group I metals.
Complete Table 2.1 to predict:
- The melting point of potassium
- The reactivity of lithium with water
| Element | Melting point/°C | Reactivity with water |
|---|---|---|
| Lithium | 181 | Reacts slowly |
| Sodium | 98 | Forms bubbles of gas rapidly |
| Potassium | Below 90 | Forms bubbles of gas very rapidly |
▶️Answer/Explanation
Answer:
The melting point of potassium is below 90°C, and the reactivity of lithium with water is reacts slowly.
Explanation:
In Group I metals, melting points decrease as you move down the group. Potassium is below sodium in the group, so its melting point is lower than sodium’s (98°C). Reactivity with water increases down the group, so lithium reacts more slowly than sodium and potassium.
Question 2(b)(Subtopic – C8.2)
Name the gas made when a Group I metal reacts with water.
▶️Answer/Explanation
Answer: The gas produced is hydrogen.
Explanation: Group I metals react with water to produce hydrogen gas and a metal hydroxide. For example, sodium reacts with water to form sodium hydroxide and hydrogen gas.
Question 2(c)(Sub-topic code: C2.4 Ions and ionic bonds)
When sodium reacts with chlorine, an orange flame is seen and the sodium melts. Sodium chloride is formed.
(i) State if the reaction is exothermic or endothermic. Explain your answer.
(ii) Sodium chloride contains chloride ions. Describe a test for chloride ions and the positive result.
(iii) State the type of bonding present in sodium chloride. Explain your answer.
▶️Answer/Explanation
Answer:
(i) The reaction is exothermic because energy is released, as indicated by the orange flame and the melting of sodium.
(ii) To test for chloride ions, add aqueous silver nitrate to the solution. A white precipitate of silver chloride will form if chloride ions are present.
(iii) The type of bonding in sodium chloride is ionic bonding. This is because sodium (a metal) transfers an electron to chlorine (a non-metal), forming oppositely charged ions that are held together by electrostatic forces.
Question 2(d)(Subtopic – C4.1)
Concentrated aqueous sodium chloride is electrolysed. State the products at the electrodes.
▶️Answer/Explanation
Answer: At the cathode, hydrogen gas is produced. At the anode, chlorine gas is produced.
Explanation: During the electrolysis of concentrated aqueous sodium chloride, hydrogen ions (H⁺) are reduced at the cathode to form hydrogen gas, while chloride ions (Cl⁻) are oxidized at the anode to form chlorine gas.
Question 2(e)(Sub-topic code: C12.4 Separation and purification)
A student separates a mixture of sand and aqueous sodium chloride.
(i) State the method of separation used to separate the sand from the aqueous sodium chloride.
(ii) Describe how solid sodium chloride can be obtained from aqueous sodium chloride.
▶️Answer/Explanation
Answer:
(i) The method used is filtration.
(ii) To obtain solid sodium chloride, the aqueous solution is heated to evaporate the water, leaving behind solid sodium chloride. This process is called evaporation or crystallization.
Explanation: Filtration is used to separate insoluble solids (like sand) from liquids. Evaporation or crystallization is used to separate a soluble solid (like sodium chloride) from a solution.
Question 3(a)(Subtopic – P3.1)
An astronomer on Earth is able to see the Moon even though the Moon does not emit visible light.
State one property of visible light that enables observation of the Moon.
▶️Answer/Explanation
Answer: Reflection
Explanation: The Moon is visible from Earth because it reflects sunlight. Visible light from the Sun hits the Moon’s surface and is reflected back to Earth, allowing us to see the Moon even though it does not emit its own visible light.
Question 3(b)(Subtopic – P3.3)
Visible light is part of the electromagnetic spectrum.
Place visible light in the correct place in the incomplete electromagnetic spectrum in Fig. 3.1.
▶️Answer/Explanation
Answer: Visible light should be placed in the middle box between ultraviolet and infrared.
Explanation: The electromagnetic spectrum is arranged in order of increasing wavelength or decreasing frequency. Visible light falls between ultraviolet (shorter wavelength) and infrared (longer wavelength).
Question 3(c)(i)(Subtopic – P1.2)
Light rays from the Moon travel at \(3 \times 10^5 \, \text{km}/\text{s}\) to reach the astronomer on Earth.
The distance travelled is 400 000 km.
Calculate the time taken for the light rays to travel from the Moon to the Earth.
▶️Answer/Explanation
Answer: 1.33 s
Explanation: To calculate the time taken, we use the formula: \[ \text{time} = \frac{\text{distance}}{\text{speed}} \] Given: \[ \text{distance} = 400\,000 \, \text{km}, \quad \text{speed} = 3 \times 10^5 \, \text{km/s} \] Substituting the values: \[ \text{time} = \frac{400\,000}{3 \times 10^5} = 1.33 \, \text{s} \] Therefore, the time taken is 1.33 seconds.
Question 3(c)(ii)(Subtopic – P3.4)
Explain why sound waves are unable to travel from the Moon to the Earth.
▶️Answer/Explanation
Answer: Sound waves cannot travel through a vacuum.
Explanation: Sound waves require a medium (such as air, water, or solid materials) to travel through. Since space between the Moon and Earth is a vacuum (no medium), sound waves cannot propagate from the Moon to the Earth.
Question 3(d)(i)(Subtopic – P3.2)
The astronomer uses lenses in a telescope to look at the Moon.
Fig. 3.2 shows rays of light passing through a lens.
On Fig. 3.2, label the focal length of the lens with a double-headed arrow (←).
▶️Answer/Explanation
Answer: The focal length should be labeled with a double-headed arrow from the center of the lens to the focal point (F).
Explanation: The focal length is the distance between the center of the lens and the focal point (F), where parallel rays of light converge after passing through the lens.
Question 3(d)(ii)(Subtopic – P3.2)
On Fig. 3.2, label the principal focus of the lens with the letter F.
▶️Answer/Explanation
Answer: The principal focus should be labeled with the letter F at the focal point.
Explanation: The principal focus (F) is the point where parallel rays of light converge after passing through the lens. It is located along the principal axis of the lens.
Question 3(e)(i)(Subtopic – P5.2)
An astronaut on the Moon is exposed to ionising background radiation.
State one effect of ionising radiation on the human body.
▶️Answer/Explanation
Answer: Cancer or mutation
Explanation: Ionising radiation can damage the DNA in cells, leading to mutations or uncontrolled cell growth, which can result in cancer. It can also cause other harmful effects such as radiation sickness or genetic mutations.
Question 3(e)(ii)(Sub-topic Code: P5.2 Radioactivity)
Suggest one source of background radiation on the Moon.
▶️Answer/Explanation
Answer: Cosmic radiation
Explanation: The Moon has no atmosphere to protect it from cosmic radiation, which comes from outer space. This radiation is a significant source of background radiation on the Moon.
Question 4 (a)(Subtopic – B13.3)
Fig. 4.1 is a diagram of a cross-section through skin tissue.
Identify the parts labelled A, B and C in Fig. 4.1.
A: …………………………………………..
B: …………………………………………..
C: …………………………………………..
▶️Answer/Explanation
Answer:
A: Sweat gland
B: Fat (fatty tissue)
C: (Hair) erector muscle
Explanation: The diagram shows a cross-section of skin tissue. Part A is the sweat gland, which is responsible for producing sweat to help regulate body temperature. Part B is the fat (fatty tissue), which acts as an insulator and energy store. Part C is the hair erector muscle, which contracts to make hair stand up, helping to trap air and provide insulation.
Question 4 (b)(Subtopic – B13.3)
Complete the sentences to describe how the body responds in cold conditions using words from the list.
Each word may be used once, more than once or not at all.
blood energy muscles skin
When the internal body temperature decreases, the brain detects the low temperature of the …………………………………………..
To increase the body temperature ………………………………………….. contract and relax rapidly. This is called shivering.
This increases the rate of respiration which releases ………………………………………….. in the form of heat.
▶️Answer/Explanation
Answer:
When the internal body temperature decreases, the brain detects the low temperature of the blood.
To increase the body temperature muscles contract and relax rapidly. This is called shivering.
This increases the rate of respiration which releases energy in the form of heat.
Explanation: In cold conditions, the body detects a drop in temperature through the blood. To generate heat, muscles contract and relax rapidly, causing shivering. This increases the rate of respiration, releasing energy in the form of heat to maintain body temperature.
Question 4 (c)(Subtopic – B13.3)
The boxes on the left show some sentence beginnings. The boxes on the right show some sentence endings.
Draw one line to link one box on the left to one box on the right to show the correct definition of homeostasis.
▶️Answer/Explanation
Answer:
Homeostasis is the maintenance of internal environment.
Explanation: Homeostasis refers to the maintenance of a stable internal environment within the body, despite changes in external conditions. It involves regulating factors such as temperature, pH, and glucose levels to ensure optimal functioning of the body’s cells and organs.
Question 5(a) (Subtopic – C10.2)
(i) State the percentage of oxygen and of nitrogen in a sample of clean air.
(ii) A sample of air collected near a busy road contains carbon monoxide. Carbon monoxide is made by car engines. Describe how carbon monoxide is made by car engines.
(iii) State one harmful effect of carbon monoxide on the health of a human.
▶️Answer/Explanation
Answer:
(i) Clean air contains approximately:
- 21% oxygen
- 78% nitrogen
(ii) Carbon monoxide is produced by the incomplete combustion of hydrocarbons in car engines. When there is insufficient oxygen, carbon reacts with oxygen to form carbon monoxide (CO) instead of carbon dioxide (CO₂).
(iii) Carbon monoxide binds to haemoglobin in red blood cells, forming carboxyhaemoglobin, which reduces the blood’s ability to carry oxygen. This can lead to oxygen deprivation, causing symptoms like dizziness, headaches, and even death in severe cases.
Explanation:
(i) Clean air is primarily composed of nitrogen (78%) and oxygen (21%), with trace amounts of other gases like argon and carbon dioxide.
(ii) Incomplete combustion occurs when there is not enough oxygen for complete combustion. Instead of producing carbon dioxide, carbon monoxide is formed, which is a toxic gas.
(iii) Carbon monoxide is dangerous because it binds to haemoglobin more strongly than oxygen, preventing oxygen from being transported around the body. This can lead to tissue damage and organ failure.
Question 5(b)(Subtopic – C10.2)
The atmosphere contains small quantities of sulfur dioxide. Sulfur dioxide causes acid rain.
(i) Suggest a pH for acid rain.
(ii) Suggest one adverse effect of acid rain on buildings.
(iii) Sulfur dioxide is made when sulfur is burned in oxygen. This reaction is called an oxidation reaction. State the meaning of the term oxidation.
▶️Answer/Explanation
Answer:
(i) The pH of acid rain is typically less than 7, often around 4-5.
(ii) Acid rain can cause the corrosion of building materials, such as limestone and marble, leading to the deterioration of structures over time.
(iii) Oxidation is the gain of oxygen or the loss of electrons by a substance during a chemical reaction.
Explanation:
(i) Acid rain has a lower pH than normal rainwater (which has a pH of around 5.6) due to the presence of acidic gases like sulfur dioxide and nitrogen oxides.
(ii) Acid rain reacts with calcium carbonate in building materials, forming soluble compounds that wash away, weakening the structure.
(iii) Oxidation involves the addition of oxygen or the removal of electrons from a substance. For example, when sulfur burns in oxygen, it forms sulfur dioxide (SO₂), which is an oxidation reaction.
Question 6(a)(i)(Subtopic – P4.3)
Fig. 6.1 shows an electric heater containing two heating elements.
The two heating elements are connected in series. Each heating element has a resistance of 8 Ω.
Calculate the combined resistance of the two heating elements.
▶️Answer/Explanation
Answer: 16 Ω
Explanation: When resistors are connected in series, their resistances add up. The formula for the total resistance in a series circuit is: \[ R_{\text{total}} = R_1 + R_2 \] Given: \[ R_1 = 8 \, \Omega, \quad R_2 = 8 \, \Omega \] Substituting the values: \[ R_{\text{total}} = 8 + 8 = 16 \, \Omega \] Therefore, the combined resistance is 16 Ω.
Question 6(a)(ii)(Subtopic – P4.3)
A different heater has the two heating elements connected in parallel.
State which value could be the combined resistance of the two heating elements connected in parallel.
Explain your answer.
▶️Answer/Explanation
Answer: 4 Ω
Explanation: When resistors are connected in parallel, the total resistance is less than the smallest individual resistance. The formula for the total resistance in a parallel circuit is: \[ \frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2} \] Given: \[ R_1 = 8 \, \Omega, \quad R_2 = 8 \, \Omega \] Substituting the values: \[ \frac{1}{R_{\text{total}}} = \frac{1}{8} + \frac{1}{8} = \frac{2}{8} = \frac{1}{4} \] Therefore: \[ R_{\text{total}} = 4 \, \Omega \] The combined resistance in parallel is 4 Ω, which is less than either of the individual resistances.
Question 6(a)(iii)(Subtopic – P4.3)
Complete the circuit diagram for the two heating elements (resistors) connected in parallel to an a.c. power supply.
The circuit should contain one switch to operate both heating elements.
▶️Answer/Explanation
Answer: The circuit diagram should show:
- Two resistors (heating elements) connected in parallel.
- A switch connected in series with the power supply to control both heating elements.
Explanation: In a parallel circuit, the resistors are connected side by side, and the same voltage is applied across each resistor. The switch is placed in the main line to control the flow of current to both resistors simultaneously.
Question 6(b)(i)(Subtopic – P2.3)
Fig. 6.2 shows the heater on a wall in a room.
When the heater is switched on, the air around the heater is warmed.
On Fig. 6.2, draw four arrows to show how the warm air circulates around the room.
▶️Answer/Explanation
Answer: The arrows should show:
- Two arrows pointing upwards near the heater (warm air rising).
- Two arrows pointing downwards away from the heater (cool air sinking).
Explanation: Warm air rises because it is less dense than cool air. As the warm air rises, it creates a convection current where cool air moves in to replace it. This results in a circular flow of air around the room.
Question 6(b)(ii)(Subtopic – P2.3)
Name the process which circulates the warm air.
▶️Answer/Explanation
Answer: Convection
Explanation: Convection is the process by which heat is transferred through the movement of fluids (liquids or gases). In this case, the warm air rises, and cool air sinks, creating a convection current that circulates the air around the room.
Question 6(c)(Subtopic – P4.2)
A man walks on the floor in the room.
As he walks, he gains a negative charge.
Describe how the man gains this charge.
Use ideas about charged particles in your answer.
▶️Answer/Explanation
Answer: The man gains a negative charge due to the transfer of electrons from the floor to his body through friction.
Explanation: When the man walks on the floor, friction between his shoes and the floor causes electrons to be transferred from the floor to his body. Electrons are negatively charged particles, so the man gains a negative charge as he accumulates these electrons. This process is known as charging by friction.
Question 7(a)(Subtopic – B6.1)
State the word equation for photosynthesis.
▶️Answer/Explanation
Answer: The word equation for photosynthesis is:
Carbon dioxide + Water → Glucose + Oxygen
Explanation: Photosynthesis is the process by which plants convert carbon dioxide and water into glucose and oxygen using light energy. This process occurs in the chloroplasts of plant cells, which contain chlorophyll to absorb light.
Question 7(b)(Subtopic – B6.2)
Fig. 7.1 is a diagram of a cross-section of a leaf.
(i) Identify the area in Fig. 7.1, A, B, C, or D, where most photosynthesis takes place. Give one reason for your answer using evidence from Fig. 7.1.
(ii) On Fig. 7.1, draw one arrow to show the pathway of water during transpiration.
(iii) State the name of part X shown in Fig. 7.1.
▶️Answer/Explanation
Answer:
(i) The area where most photosynthesis takes place is B (palisade mesophyll). This is because it contains the most chloroplasts, which are responsible for photosynthesis.
(ii) The arrow should point from the xylem (in the vascular bundle) to the stomata on the leaf surface.
(iii) Part X is the cuticle.
Explanation: The palisade mesophyll is the primary site of photosynthesis due to its high concentration of chloroplasts. Water moves from the xylem through the leaf and exits via the stomata during transpiration. The cuticle is a waxy layer that reduces water loss from the leaf surface.
Question 7(c)(Subtopic – B6.1)
A group of pea plants is grown with standard fertiliser and another group is grown with fertiliser containing additional magnesium. The height of the plants is measured and an average calculated. Table 7.1 shows the results.
| Group of pea plant | Average height of plant/cm |
|---|---|
| Standard fertiliser | 27.4 |
| Fertiliser with additional magnesium | 33.0 |
Carbohydrates are needed for plant growth. Explain the results shown in Table 7.1. Include ideas about carbohydrates and photosynthesis in your answer.
▶️Answer/Explanation
Answer:
The plants grown with additional magnesium were taller because magnesium is essential for the production of chlorophyll, which is required for photosynthesis. With more chlorophyll, the plants can produce more carbohydrates (glucose) through photosynthesis, leading to increased growth.
Explanation: Magnesium is a key component of chlorophyll, the pigment that absorbs light for photosynthesis. Without sufficient magnesium, chlorophyll production is reduced, limiting the plant’s ability to photosynthesize and produce carbohydrates. The additional magnesium in the fertiliser allowed the plants to produce more chlorophyll, resulting in more efficient photosynthesis and greater growth.
Question 7(d)(Sub-topic code: B6.1)
Fertilisers contain nitrate ions. Describe the importance of nitrate ions to plants.
▶️Answer/Explanation
Answer: Nitrate ions are essential for the synthesis of amino acids, which are the building blocks of proteins. Proteins are required for growth and repair in plants.
Explanation: Nitrate ions are absorbed by plant roots and used to produce amino acids. These amino acids are then used to synthesise proteins, which are vital for cellular functions, growth, and repair. Without nitrate ions, plants cannot produce sufficient proteins, leading to stunted growth.
Question 8(a)(i)(Subtopic – C2.2)
An atom of aluminium has a proton number of 13 and a nucleon number of 27.
State what is meant by the term nucleon number.
▶️Answer/Explanation
Answer: The nucleon number is the total number of protons and neutrons in the nucleus of an atom.
Explanation: The nucleon number (also known as the mass number) is the sum of the number of protons and neutrons in the nucleus of an atom. For aluminium, the nucleon number is 27, which means there are 13 protons and 14 neutrons in its nucleus.
Question 8(a)(ii)(Subtopic – C2.2)
Describe the electronic structure of an atom of aluminium.
You may wish to draw a diagram to help your answer.
▶️Answer/Explanation
Answer: The electronic structure of aluminium is 2.8.3.
Explanation: The electronic structure of an atom describes how electrons are arranged in energy levels (shells) around the nucleus. For aluminium (atomic number 13), the electrons are distributed as follows:
- First shell: 2 electrons
- Second shell: 8 electrons
- Third shell: 3 electrons
This can be represented as 2.8.3.
Question 8(b)(i)(Sub-topic Code: C9.6 Extraction of metals)
Aluminium is extracted from its ore by electrolysis.
Name one ore from which aluminium is extracted.
▶️Answer/Explanation
Answer: Bauxite
Explanation: Bauxite is the primary ore from which aluminium is extracted. It contains aluminium oxide (Al2O3), which is processed to obtain pure aluminium through electrolysis.
Question 8(b)(ii)(Subtopic – C6.1)
Electrolysis results in a chemical change.
Explain what is meant by a chemical change.
▶️Answer/Explanation
Answer: A chemical change involves the formation of new substances with different chemical properties.
Explanation: A chemical change occurs when substances react to form new products with different chemical compositions and properties. In electrolysis, aluminium oxide is broken down into aluminium and oxygen, which are new substances with different properties from the original compound.
Question 8(c)(i)(Subtopic – C9.3)
Aluminium alloys are used in aircraft parts.
State what is meant by the term alloy.
▶️Answer/Explanation
Answer: An alloy is a mixture of a metal with one or more other elements, usually metals.
Explanation: Alloys are created by mixing a metal with other elements to improve its properties, such as strength, hardness, or resistance to corrosion. For example, aluminium alloys are used in aircraft because they are lightweight and strong.
Question 8(c)(ii)(Subtopic – C9.3)
State why aluminium alloys are used in aircraft parts.
▶️Answer/Explanation
Answer: Aluminium alloys are used in aircraft parts because they have a low density and are strong.
Explanation: Aluminium alloys are lightweight (low density) and have high strength, making them ideal for aircraft construction. These properties help reduce the overall weight of the aircraft, improving fuel efficiency and performance.
Question 8(c)(iii)(Subtopic – C9.3)
State why aluminium is used in the form of alloys rather than as pure aluminium.
▶️Answer/Explanation
Answer: Alloys are stronger than pure aluminium.
Explanation: Pure aluminium is relatively soft and not very strong. By forming alloys with other elements, the strength and durability of aluminium are significantly improved, making it more suitable for structural applications like aircraft parts.
Question 8(c)(iv)(Subtopic – C9.3)
Describe and explain one other use of aluminium.
▶️Answer/Explanation
Answer: Aluminium is used in food containers because it is resistant to corrosion.
Explanation: Aluminium forms a protective oxide layer on its surface, which prevents further corrosion. This makes it ideal for use in food containers, as it does not react with food or degrade over time, ensuring the safety and longevity of the containers.
Question 9 (a)(Subtopic – P1.6.1)
Choose words from the list below to complete the sentences that describe the energy changes occurring when a wind turbine is used.
Each word may be used once, more than once or not at all.
electrical kinetic light potential thermal sound
The kinetic energy of the wind is transferred to the ………………………………………….. energy of the moving rotor blades of the wind turbine.
The useful output energy from the wind turbine is ………………………………………….. energy.
The wind turbine makes sound energy which is unwanted. Another unwanted form of energy made by wind turbines is ………………………………………….. energy.
▶️Answer/Explanation
Answer:
The kinetic energy of the wind is transferred to the kinetic energy of the moving rotor blades of the wind turbine.
The useful output energy from the wind turbine is electrical energy.
The wind turbine makes sound energy which is unwanted. Another unwanted form of energy made by wind turbines is thermal energy.
Explanation: – The wind’s kinetic energy is transferred to the rotor blades, which also have kinetic energy as they spin. – The wind turbine converts this kinetic energy into electrical energy, which is the useful output. – Sound energy is an unwanted byproduct, and some energy is also lost as heat (thermal energy) due to friction and inefficiencies in the system.
Question 9 (b)(Subtopic – P1.6.3)
State one advantage of using wind rather than coal to generate electricity.
▶️Answer/Explanation
Answer:
Wind energy is renewable and does not produce greenhouse gases, unlike coal.
Explanation: Wind energy is a renewable resource, meaning it will not run out, whereas coal is a finite resource. Additionally, wind turbines do not emit greenhouse gases or pollutants during operation, making them more environmentally friendly compared to coal-fired power plants.
Question 9 (c)(Subtopic – P3.4)
One disadvantage of wind turbines is they give out very low frequency sound waves.
(i) State what is meant by the frequency of a wave.
(ii) The frequency of the sound waves produced is very low.
A healthy human ear can only just hear this sound.
Suggest a value for this frequency.
………………………………………….. Hz
▶️Answer/Explanation
Answer:
(i) Frequency is the number of waves produced per second or passing a fixed point per second.
(ii) A suggested value for the frequency is 20 Hz.
Explanation: (i) Frequency is a measure of how many wave cycles occur in one second, measured in Hertz (Hz). (ii) The human ear can typically hear sounds in the range of 20 Hz to 20,000 Hz. Very low-frequency sounds, such as those produced by wind turbines, are often at the lower end of this range, around 20 Hz.
Question 9 (d)(Subtopic – P4.1)
Magnets are used in the generators of wind turbines.
Fig. 9.1 shows a bar magnet.
On Fig. 9.1, draw the pattern and direction of the magnetic field lines around the magnet.
▶️Answer/Explanation
Answer:
The magnetic field lines should be drawn from the north pole (N) to the south pole (S) of the magnet, curving outward and forming closed loops.
Explanation: Magnetic field lines represent the direction and strength of the magnetic field. They always flow from the north pole to the south pole outside the magnet and form continuous loops. The closer the lines, the stronger the magnetic field.
Question 9 (e)(Subtopic Code: P5.2)
Another method of generating electricity is to use nuclear fission in a nuclear power station.
During nuclear fission, α-particles, β-particles and γ-rays may be released from atoms.
(i) Complete Table 9.1 to show the properties of α-particles, β-particles and γ-rays.
Table 9.1
| Radiation | Ionising ability | Nature | Penetrating ability |
|---|---|---|---|
| α-particle | High | Helium nucleus | Low |
| β-particle | Medium | Electron | Medium |
| γ-ray | Low | Electromagnetic wave | High |
(ii) Describe what happens to the nucleus of an atom during nuclear fission.
▶️Answer/Explanation
Answer:
(i) Table 9.1 completed as above.
(ii) During nuclear fission, the nucleus of an atom splits into two smaller nuclei, releasing energy and emitting α-particles, β-particles, and γ-rays.
Explanation: (i) α-particles are helium nuclei with high ionising ability but low penetration. β-particles are electrons with medium ionising and penetrating ability. γ-rays are electromagnetic waves with low ionising ability but high penetration. (ii) Nuclear fission involves the splitting of a heavy nucleus (e.g., uranium-235) into smaller nuclei, releasing a large amount of energy and radiation in the process.
Question 10(a)(Subtopic – B5.1)
A student writes a definition of an enzyme. The definition is not correct. ‘Enzymes are fats that function as chemical catalysts.’ Circle the two words in the student’s definition that are not correct.
The two incorrect words in the definition are fats and chemical.
▶️Answer/Explanation
Answer: The two incorrect words in the definition are fats and chemical.
Explanation: Enzymes are proteins, not fats, and they function as biological catalysts, not chemical catalysts. Enzymes speed up biochemical reactions in living organisms without being consumed in the process.
Question 10(b)(Subtopic – B4.1)
Enzymes are used to break down large molecules into smaller molecules. Table 10.1 shows some large molecules and the smaller molecules they are made from. Complete Table 10.1.
| Large molecules | Smaller molecules |
|---|---|
| 1. Starch | Glucose |
| 2. Glycogen | Glucose |
| Proteins | Amino acids |
| Fats | 1. Fatty acids 2. Glycerol |
▶️Answer/Explanation
Answer: The completed table is shown above.
Explanation:
- Starch and glycogen are broken down into glucose by enzymes like amylase.
- Proteins are broken down into amino acids by enzymes like proteases.
- Fats are broken down into fatty acids and glycerol by enzymes like lipase.
Question 10(c)(Subtopic – B4.1)
List the three chemical elements that make up fats.
▶️Answer/Explanation
Answer: The three chemical elements that make up fats are:
- Carbon
- Hydrogen
- Oxygen
Explanation: Fats are composed of carbon, hydrogen, and oxygen atoms. They are a type of lipid and are made up of fatty acids and glycerol.
Question 10(d)(Subtopic – B5.1)
Fig. 10.1 is a graph showing the enzyme activity at different temperatures of four different enzymes, A, B, C, and D.
Table 10.2 shows average temperatures in different environments.
(i) Describe the effect of temperature on the enzyme activity of enzyme B. Use data to support your answer.
(ii) Use Fig. 10.1 and Table 10.2 to identify the enzyme, A, B, C, or D, found in bacteria that can survive in:
▶️Answer/Explanation
Answer:
(i) Enzyme B’s activity increases as the temperature rises, reaching a peak at around 33°C, after which the activity decreases sharply. This indicates that enzyme B has an optimum temperature of 33°C.
(ii) The enzymes are:
- Hydrothermal vent regions: Enzyme D (optimum temperature around 95°C)
- Arctic seas: Enzyme A (optimum temperature around -2°C)
- The same environment as enzyme C: Enzyme D (both have high-temperature optima)
Explanation:
(i) Enzyme activity increases with temperature up to the optimum temperature, after which the enzyme denatures and activity decreases. Enzyme B’s optimum temperature is 33°C.
(ii) Enzymes have specific temperature ranges at which they function best. Enzyme D is adapted to high temperatures (hydrothermal vents), while Enzyme A is adapted to low temperatures (arctic seas). Enzyme C and D both function in high-temperature environments.
Question 11(a)(Subtopic – C10.2)
Methane is a greenhouse gas.
Name one other greenhouse gas.
▶️Answer/Explanation
Answer: Carbon dioxide (CO2)
Explanation: Greenhouse gases trap heat in the Earth’s atmosphere, contributing to global warming. Carbon dioxide is one of the most common greenhouse gases, along with methane, water vapor, and nitrous oxide.
Question 11(b)(Subtopic – C6.2)
Methane is completely combusted in oxygen. Carbon dioxide and water are made.
Balance the symbol equation for this reaction.
▶️Answer/Explanation
Answer: (CH4 +) 2 (O2 → CO2 +) 2 (H2O) ;;
Explanation: The balanced equation for the complete combustion of methane is: \[ \text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} \] This equation is balanced because there are equal numbers of each type of atom on both sides of the equation:
- 1 carbon atom on both sides
- 4 hydrogen atoms on both sides
- 4 oxygen atoms on both sides
Question 11(c)(Subtopic – C11.1)
Complete Fig. 11.1 to show the structural formula of methane.
▶️Answer/Explanation
Answer: The structural formula of methane is: \[ \text{H} – \text{C} – \text{H} \] \[ \quad \quad \text{H} \quad \text{H} \]
Explanation: Methane (CH4) consists of one carbon atom bonded to four hydrogen atoms in a tetrahedral arrangement. The structural formula shows the arrangement of atoms and bonds in the molecule.
Question 11(d)(i)(Subtopic – C11.3 )
Methane is the main constituent of a fossil fuel.
Name this fossil fuel.
▶️Answer/Explanation
Answer: Natural gas
Explanation: Methane is the primary component of natural gas, which is a fossil fuel used for heating, cooking, and electricity generation.
Question 11(d)(ii)(Subtopic – C11.3)
Name one other fossil fuel.
▶️Answer/Explanation
Answer: Coal
Explanation: Coal is another fossil fuel, formed from the remains of ancient plants. It is primarily composed of carbon and is used for electricity generation and industrial processes.
Question 11(e)(i)(Subtopic – C11.5)
Methane is an alkane. Ethene is an alkene.
State the difference in structure between an alkane and an alkene.
▶️Answer/Explanation
Answer: Alkanes have only single bonds between carbon atoms, while alkenes have at least one double bond between carbon atoms.
Explanation: Alkanes are saturated hydrocarbons with single bonds (C-C), while alkenes are unsaturated hydrocarbons with at least one double bond (C=C). For example, methane (CH4) is an alkane, and ethene (C2H4) is an alkene.
Question 11(e)(ii)(Subtopic – C11.5)
A student uses a chemical reagent to show the difference between an alkane and an alkene.
Tick (✓) the correct box to show the chemical reagent used.
aqueous bromine
limewater
litmus
universal indicator
▶️Answer/Explanation
Answer: Aqueous bromine
Explanation: Aqueous bromine is used to distinguish between alkanes and alkenes. Alkenes react with bromine, causing the orange-brown color of bromine to disappear, while alkanes do not react. This is because alkenes have a double bond that can undergo addition reactions.
Question 11(f)(Subtopic – C11.6)
Ethene, C2H4, reacts with steam to produce ethanol, C2H5OH.
Ethene is a hydrocarbon. Explain why ethanol is not a hydrocarbon.
▶️Answer/Explanation
Answer: Ethanol contains oxygen, while hydrocarbons contain only hydrogen and carbon.
Explanation: Hydrocarbons are compounds that contain only hydrogen and carbon atoms. Ethanol (C2H5OH) contains an oxygen atom in addition to hydrogen and carbon, so it is not a hydrocarbon. It is classified as an alcohol.
Question 12 (a)(Subtopic – P1.5.1)
Fig. 12.1 shows the horizontal forces acting on a motorcyclist and his motorcycle.
(i) Calculate the resultant horizontal force acting on the motorcyclist and motorcycle.
Force: ………………………………………….. N
(ii) Describe how this resultant force changes the speed of the motorcycle.
▶️Answer/Explanation
Answer:
(i) Resultant force: 300 N
(ii) The resultant force causes the motorcycle to slow down.
Explanation: (i) The resultant force is calculated by subtracting the backward force (e.g., friction or air resistance) from the forward force (e.g., engine thrust). For example, if the forward force is 500 N and the backward force is 200 N, the resultant force is 500 N – 200 N = 300 N. (ii) A resultant force in the opposite direction of motion (backward) acts to decelerate the motorcycle, reducing its speed.
Question 12 (b)(Subtopic – P1.2)
Fig. 12.2 shows a speed-time graph for the motorcycle’s journey over 80 s.
(i) State a time when the motorcycle is not moving.
………………………………………….. s
(ii) On Fig. 12.2, label with the letter C a point when the motorcycle is moving at a constant speed.
(iii) On Fig. 12.2, label with the letter S a point when the speed of the motorcycle is increasing.
▶️Answer/Explanation
Answer:
(i) The motorcycle is not moving at 0 s, 40 s to 45 s, or 80 s.
(ii) Label a point between t = 15 s and t = 30 s or between t = 60 s and t = 70 s with the letter C.
(iii) Label a point between t = 0 s and t = 15 s or between t = 45 s and t = 60 s with the letter S.
Explanation: (i) The motorcycle is stationary when the speed is zero, which occurs at the start (0 s), during a pause (40 s to 45 s), and at the end (80 s). (ii) Constant speed is represented by a horizontal line on the speed-time graph. This occurs between 15 s and 30 s or between 60 s and 70 s. (iii) Increasing speed is represented by an upward-sloping line on the speed-time graph. This occurs between 0 s and 15 s or between 45 s and 60 s.
Question 12 (c)(Subtopic – P3.4 )
The motorcycle produces a loud sound with a high frequency when moving.
Describe the pitch and amplitude of the sound waves produced.
Pitch:
Amplitude:
▶️Answer/Explanation
Answer:
Pitch: High
Amplitude: Large
Explanation: – Pitch is determined by the frequency of the sound wave. A high-frequency sound corresponds to a high pitch. – Amplitude is related to the loudness of the sound. A loud sound has a large amplitude.
Question 12 (d)(Subtopic – P2.1.3)
As the motorcycle moves along the road, the temperature of the air in the tyres increases.
Explain why the pressure of the air in the tyres increases.
▶️Answer/Explanation
Answer:
increased kinetic energy / speed (of molecules) ;
more frequent collisions with tyre ;
Explanation: According to the kinetic theory of gases, an increase in temperature causes gas molecules to gain kinetic energy and move faster. This results in more frequent and forceful collisions with the walls of the tyre, leading to an increase in pressure.