1. (a) Sensitivity is one of the characteristics of living organisms. Define the term sensitivity.
▶️Answer/Explanation
Answer: Sensitivity is the ability to detect and respond to changes in the environment.
Sub-topic Code: B1.1 (Characteristics of Living Organisms)
Detailed Solution: Sensitivity refers to the ability of living organisms to detect changes in their environment (stimuli) and respond to them appropriately. This is essential for survival, as it allows organisms to adapt to their surroundings.
1. (b) (i) Draw an X on Fig. 1.1 to identify the position of the blind spot.
▶️Answer/Explanation
Answer: X drawn on blind spot
Sub-topic Code: B10.1 (Human Eye)
Detailed Solution: The blind spot is the area on the retina where the optic nerve exits the eye. It lacks photoreceptor cells, so it cannot detect light. The X should be placed at the position where the optic nerve connects to the retina.
1. (b) (ii) Identify the letter from Fig. 1.1 that shows the part that:
contains receptor cells ……
controls the amount of light entering the eye ……
refracts light. ……
▶️Answer/Explanation
Answer: H (contains receptor cells); B (controls the amount of light entering the eye); C (refracts light)
Sub-topic Code: B10.1 (Human Eye)
Detailed Solution: – H represents the retina, which contains photoreceptor cells (rods and cones) that detect light. – B represents the iris, which controls the amount of light entering the eye by adjusting the size of the pupil. – C represents the lens, which refracts light to focus it onto the retina.
1. (b) (iii) A person changes their focus from a near object to a distant object. Describe the changes that occur to the parts labelled A, E, and F in Fig. 1.1 when focusing on a distant object.
▶️Answer/Explanation
Answer: A becomes thinner; E tightens/stretches; F relaxes
Sub-topic Code: B10.1 (Human Eye)
Detailed Solution: – A (lens) becomes thinner to reduce its refractive power, allowing light from distant objects to focus on the retina. – E (ciliary muscles) tighten or stretch to flatten the lens. – F (suspensory ligaments) relax, reducing tension on the lens.
1. (c) The eye forms part of the peripheral nervous system. Name the two parts of the central nervous system.
▶️Answer/Explanation
Answer: brain; spinal cord
Sub-topic Code: B10.1 (Nervous System)
Detailed Solution: The central nervous system (CNS) consists of the brain and the spinal cord. The CNS processes information received from the peripheral nervous system (PNS), which includes nerves outside the brain and spinal cord.
2. (a) (i) Explain what is meant by an isotope.
▶️Answer/Explanation
Answer: Atoms with the same proton number but different nucleon number (or number of neutrons).
Sub-topic Code: C16.1 (Atomic Structure)
Detailed Solution: Isotopes are atoms of the same element that have the same number of protons (and electrons) but different numbers of neutrons. This results in different mass numbers (nucleon numbers) for the same element.
2. (a) (ii) Complete Table 2.1 to give the number of particles in a potassium atom and a potassium ion.
▶️Answer/Explanation
Answer: – 2(a)(ii)
Potassium atom: 19 protons, 19 electrons, 20 neutrons. – Potassium ion: 19 protons, 18 electrons, 20 neutrons.
Sub-topic Code: C16.1 (Atomic Structure)
Detailed Solution: – A potassium atom (K) has 19 protons, 19 electrons, and 20 neutrons (since the nucleon number is 39). – A potassium ion (K⁺) loses one electron, so it has 19 protons, 18 electrons, and 20 neutrons.
2. (b) Sodium reacts with water. Sodium hydroxide, NaOH, and hydrogen are made. Construct the balanced symbol equation for this reaction.
▶️Answer/Explanation
Answer: 2Na + 2H₂O → 2NaOH + H₂
Sub-topic Code: C9.1 (Chemical Reactions)
Detailed Solution: Sodium reacts with water to produce sodium hydroxide and hydrogen gas. The balanced equation is: \[ 2Na + 2H₂O \rightarrow 2NaOH + H₂ \]
2. (c) Complete the dot-and-cross diagram in Fig. 2.2 to show the electronic structure of a sodium ion and a fluoride ion.
▶️Answer/Explanation
Answer: 2(c)
Sodium ion (Na⁺) has 10 electrons; fluoride ion (F⁻) has 10 electrons.
Sub-topic Code: C17.1 (Chemical Bonding)
Detailed Solution: – Sodium (Na) loses one electron to form Na⁺, which has 10 electrons. – Fluorine (F) gains one electron to form F⁻, which also has 10 electrons. – The dot-and-cross diagram should show the transfer of one electron from sodium to fluorine.
2. (d) (i) The flame colour turns from blue to yellow. State the name of the metal ion in compound X.
▶️Answer/Explanation
Answer: Sodium ion (Na⁺)
Sub-topic Code: C9.1 (Chemical Tests)
Detailed Solution: A yellow flame indicates the presence of sodium ions (Na⁺). Sodium compounds produce a characteristic yellow flame in a flame test.
2. (d) (ii) A white precipitate is formed. Suggest which halide ion is in compound X.
▶️Answer/Explanation
Answer: Chloride (Cl⁻)
Sub-topic Code: C9.1 (Chemical Tests)
Detailed Solution: A white precipitate with silver nitrate indicates the presence of chloride ions (Cl⁻). The reaction forms silver chloride (AgCl), which is insoluble in water.
3. (a) (i) Show that the average speed of the train during this journey is 50 m/s.
▶️Answer/Explanation
Answer: 180,000 m / 3,600 s = 50 m/s
Sub-topic Code: P1.1 (Motion)
Detailed Solution: – Distance = 180 km = 180,000 m – Time = 1 hour = 3,600 s – Speed = Distance / Time = 180,000 / 3,600 = 50 m/s
3. (a) (ii) Calculate the average kinetic energy of the train during this journey.
▶️Answer/Explanation
Answer: 850,000,000 J
Sub-topic Code: P1.1 (Motion)
Detailed Solution: – Kinetic energy (KE) = ½ mv² – Mass (m) = 680,000 kg – Speed (v) = 50 m/s – KE = ½ × 680,000 × (50)² = 850,000,000 J
3. (b) (i) Calculate the speed of sound in air.
▶️Answer/Explanation
Answer: 330 m/s
Sub-topic Code: P7.1 (Sound)
Detailed Solution: – Speed of sound = Frequency × Wavelength – Frequency = 250 Hz – Wavelength = 1.32 m – Speed = 250 × 1.32 = 330 m/s
3. (b) (ii) Describe how the sound wave travels through the air.
▶️Answer/Explanation
Answer: Vibrations of air particles create compressions and rarefactions.
Sub-topic Code: P7.1 (Sound)
Detailed Solution: Sound waves travel through air as longitudinal waves. The air particles vibrate back and forth, creating regions of high pressure (compressions) and low pressure (rarefactions).
3. (c) (i) Calculate the volume of each length of rail.
▶️Answer/Explanation
Answer: 0.04 m³
Sub-topic Code: P4.1 (Density)
Detailed Solution: – Density = Mass / Volume – Volume = Mass / Density = 324 kg / 8,100 kg/m³ = 0.04 m³
3. (c) (ii) Explain why the lengths of train track are laid with small gaps between them.
▶️Answer/Explanation
Answer: To allow for thermal expansion and prevent buckling.
Sub-topic Code: P4.1 (Thermal Properties)
Detailed Solution: The gaps between train tracks allow the metal to expand when heated (due to temperature changes) without causing the tracks to buckle or bend.
4. (a) (i) Explain the results for test-tube 2.
▶️Answer/Explanation
Answer: Boiled lipase is denatured and cannot digest fat.
Sub-topic Code: B5.1 (Enzymes)
Detailed Solution: Boiling lipase denatures the enzyme, destroying its active site. As a result, the enzyme cannot catalyze the breakdown of fat into fatty acids and glycerol, so the indicator does not turn pink.
4. (a) (ii) Calculate the difference in time taken for the indicator to turn pink between test-tubes 1 and 3.
▶️Answer/Explanation
Answer: 182 seconds
Sub-topic Code: B5.1 (Enzymes)
Detailed Solution: – Time for test-tube 1 = 378 seconds – Time for test-tube 3 = 196 seconds – Difference = 378 – 196 = 182 seconds
4. (a) (iii) Explain the difference between the results for test-tube 1 and 3.
▶️Answer/Explanation
Answer: Bile emulsifies fat, increasing the surface area for lipase to act.
Sub-topic Code: B5.1 (Enzymes)
Detailed Solution: Bile emulsifies fat, breaking it into smaller droplets. This increases the surface area available for lipase to act, speeding up the digestion of fat into fatty acids and glycerol.
4. (b) State the name of the organ that produces bile.
▶️Answer/Explanation
Answer: Liver
Sub-topic Code: B7.1 (Digestive System)
Detailed Solution: Bile is produced by the liver and stored in the gallbladder. It helps in the digestion of fats.
4. (c) (i) Explain how villi increase the rate of absorption of digested food.
▶️Answer/Explanation
Answer: Villi increase the surface area for absorption.
Sub-topic Code: B7.1 (Digestive System)
Detailed Solution: Villi are finger-like projections in the small intestine that increase the surface area for absorption of digested nutrients into the bloodstream.
4. (c) (ii) State the part of the alimentary canal where villi are found.
▶️Answer/Explanation
Answer: Small intestine
Sub-topic Code: B7.1 (Digestive System)
Detailed Solution: Villi are found in the small intestine, where most of the absorption of digested food occurs.
5. (a) Write down the molecular formula of propene.
▶️Answer/Explanation
Answer: C₃H₆
Sub-topic Code: C2.1 (Hydrocarbons)
Detailed Solution: Propene is an unsaturated hydrocarbon with the molecular formula C₃H₆, containing a double bond between two carbon atoms.
5. (b) State which group of hydrocarbons propene belongs to.
▶️Answer/Explanation
Answer: Alkenes
Sub-topic Code: C2.1 (Hydrocarbons)
Detailed Solution: Propene belongs to the alkenes, which are hydrocarbons containing at least one carbon-carbon double bond.
5. (c) State what is meant by the word unsaturated.
▶️Answer/Explanation
Answer: Contains a carbon-carbon double bond.
Sub-topic Code: C2.1 (Hydrocarbons)
Detailed Solution: Unsaturated hydrocarbons contain at least one carbon-carbon double or triple bond, allowing them to undergo addition reactions.
5. (d) State the name of this type of reaction.
▶️Answer/Explanation
Answer: Addition reaction / Hydrogenation
Sub-topic Code: C2.1 (Hydrocarbons)
Detailed Solution: The reaction of propene with hydrogen to form propane is an addition reaction, specifically hydrogenation, where hydrogen is added across the double bond.
5. (e) State what you would see when aqueous bromine is added to propene and propane.
▶️Answer/Explanation
Answer: Propene: orange to colorless; Propane: no change
Sub-topic Code: C2.1 (Hydrocarbons)
Detailed Solution: – Propene (an alkene) reacts with aqueous bromine, causing the orange color to disappear (decolorization). – Propane (an alkane) does not react with aqueous bromine, so the orange color remains unchanged.
5. (f) (i) Complete Fig. 5.3 to show the structure of poly(propene).
▶️Answer/Explanation
Answer: – 5(f)(i)
The structure should show repeating units of propene (C₃H₆) with the double bond converted into a single bond.
Sub-topic Code: C2.1 (Polymers)
Detailed Solution: Poly(propene) is formed by the addition polymerization of propene monomers. The double bond in propene breaks, and the monomers link together to form a long-chain polymer.
5. (f) (ii) Describe the differences between addition polymerisation and condensation polymerisation.
▶️Answer/Explanation
Answer: – Addition polymerization: One large molecule is formed; no by-products. – Condensation polymerization: One larger and one smaller molecule are formed; water is often produced as a by-product.
Sub-topic Code: C2.1 (Polymers)
Detailed Solution: – Addition polymerization involves the joining of monomers with double bonds to form a single large polymer molecule, with no by-products. – Condensation polymerization involves the joining of monomers with the elimination of a small molecule (e.g., water) as a by-product.
6. (a) Calculate the work done in lifting a 15 kg child to the top of the slide.
▶️Answer/Explanation
Answer: 270 J
Sub-topic Code: P3.1 (Work and Energy)
Detailed Solution: – Work done = Force × Distance – Force = Mass × Gravitational field strength = 15 kg × 10 N/kg = 150 N – Distance = 1.8 m – Work done = 150 N × 1.8 m = 270 J
6. (b) Describe how the motion of the child changes as they slide down the plastic slide.
▶️Answer/Explanation
Answer: The child accelerates initially, then decelerates as friction increases.
Sub-topic Code: P1.1 (Motion)
Detailed Solution: – Initially, the child accelerates due to gravity. – As the child slides, friction between the slide and the child increases, causing deceleration.
6. (c) Describe how the child becomes positively charged.
▶️Answer/Explanation
Answer: Electrons are transferred from the child to the slide due to friction.
Sub-topic Code: P8.1 (Static Electricity)
Detailed Solution: – Friction between the child and the slide causes electrons to transfer from the child to the slide. – This leaves the child with a net positive charge.
6. (d) Complete the sentences below using the words more or less.
▶️Answer/Explanation
Answer: – A white plastic slide will absorb infrared radiation less than a black plastic slide. – A white plastic slide will reflect infrared radiation more than a black plastic slide. – On a sunny day, a white plastic slide will heat up less than a black plastic slide.
Sub-topic Code: P4.1 (Thermal Properties)
Detailed Solution: – White surfaces reflect more infrared radiation and absorb less, so they heat up less. – Black surfaces absorb more infrared radiation and reflect less, so they heat up more.
7. (a) Put ticks (✓) in Table 7.1 to show all the terms used to describe each organism.
▶️Answer/Explanation
Answer: – 7(a)
Arctic cod: carnivore, quaternary consumer – Krill: herbivore – Orca: carnivore, quaternary consumer – Phytoplankton: producer
Sub-topic Code: B13.1 (Food Chains and Webs)
Detailed Solution: – Arctic cod and orca are carnivores and quaternary consumers. – Krill is a herbivore. – Phytoplankton is a producer.
7. (b) Describe how producers are able to make their own carbohydrates.
▶️Answer/Explanation
Answer: Through photosynthesis, using light energy, carbon dioxide, and water.
Sub-topic Code: B6.1 (Photosynthesis)
Detailed Solution: Producers (e.g., plants, phytoplankton) use photosynthesis to convert light energy, carbon dioxide, and water into glucose (a carbohydrate) and oxygen.
7. (c) Describe three ways energy is lost between trophic levels.
▶️Answer/Explanation
Answer: – Heat loss through respiration. – Energy lost in excretion (e.g., urea, faeces). – Energy used for movement and metabolic processes.
Sub-topic Code: B13.1 (Energy Transfer)
Detailed Solution: – Energy is lost as heat during respiration. – Energy is lost in waste products like urea and faeces. – Energy is used by organisms for movement and other metabolic processes.
7. (d) (i) Complete the sentences to describe the process of adaptation.
▶️Answer/Explanation
Answer: – Adaptation results from the process of natural selection. – Some organisms are better adapted to the environment than others. – These organisms survive and breed, passing on their alleles. – This process takes many generations.
Sub-topic Code: B12.1 (Evolution)
Detailed Solution: – Natural selection favors organisms with advantageous traits, allowing them to survive and reproduce. – Over many generations, these traits become more common in the population.
7. (d) (ii) List two features of gas exchange surfaces.
▶️Answer/Explanation
Answer: – Thin walls for short diffusion distance. – Large surface area for efficient gas exchange.
Sub-topic Code: B8.1 (Gas Exchange)
Detailed Solution: – Gas exchange surfaces (e.g., gills, alveoli) have thin walls to reduce the diffusion distance. – They also have a large surface area to maximize the rate of gas exchange.
8. (a) Use the order of reactivity and the information in Table 8.1 to predict the missing results.
▶️Answer/Explanation
Answer: – Mg in FeSO₄: dark grey metal, pale green solution. – Fe in CuSO₄: pink/brown metal, pale blue solution. – Zn in CuSO₄: dark grey metal, pale blue solution.
Sub-topic Code: C9.1 (Reactivity Series)
Detailed Solution: – Magnesium (Mg) is more reactive than iron (Fe), so it displaces iron from FeSO₄, forming dark grey iron and a pale green solution. – Iron (Fe) is more reactive than copper (Cu), so it displaces copper from CuSO₄, forming pink/brown copper and a pale blue solution. – Zinc (Zn) is more reactive than copper (Cu), so it displaces copper from CuSO₄, forming dark grey copper and a pale blue solution.
8. (b) Construct the balanced symbol equation for the reaction between zinc and iron sulfate.
▶️Answer/Explanation
Answer: Zn(s) + FeSO₄(aq) → Fe(s) + ZnSO₄(aq)
Sub-topic Code: C9.1 (Reactivity Series)
Detailed Solution: – Zinc (Zn) displaces iron (Fe) from iron sulfate (FeSO₄), forming iron and zinc sulfate (ZnSO₄). – The balanced equation is: \[ Zn(s) + FeSO₄(aq) \rightarrow Fe(s) + ZnSO₄(aq) \]
8. (c) Construct the balanced ionic half-equation for the reaction between magnesium and zinc sulfate.
▶️Answer/Explanation
Answer: Mg → Mg²⁺ + 2e⁻
Sub-topic Code: C19.1 (Electrolysis)
Detailed Solution: – Magnesium (Mg) loses two electrons to form magnesium ions (Mg²⁺). – The half-equation is: \[ Mg \rightarrow Mg^{2+} + 2e^- \]
8. (d) (i) Calculate the maximum mass of magnesium chloride that can be made from 0.48 g of magnesium.
▶️Answer/Explanation
Answer: 1.9 g
Sub-topic Code: C9.1 (Stoichiometry)
Detailed Solution: – Moles of Mg = Mass / Molar mass = 0.48 g / 24 g/mol = 0.02 mol – Moles of MgCl₂ = 0.02 mol (1:1 ratio) – Mass of MgCl₂ = Moles × Molar mass = 0.02 mol × 95 g/mol = 1.9 g
8. (d) (ii) State the test for hydrogen gas and give the observation for a positive result.
▶️Answer/Explanation
Answer: Test: lighted splint; Observation: squeaky pop
Sub-topic Code: C9.1 (Chemical Tests)
Detailed Solution: – Hydrogen gas is tested by holding a lighted splint near the gas. – A positive result is indicated by a squeaky pop sound as the hydrogen ignites.
9. (a) (i) Calculate the weight of the mass hanging from spring A.
▶️Answer/Explanation
Answer: 0.6 N
Sub-topic Code: P2.1 (Forces)
Detailed Solution: – Extension = Extended length – Unloaded length = 3.4 cm – 2.2 cm = 1.2 cm – Force = Spring constant × Extension = 0.50 N/cm × 1.2 cm = 0.6 N
9. (a) (ii) State and explain which of the three springs has the largest spring constant.
▶️Answer/Explanation
Answer: Spring B; smallest extension for the same mass
Sub-topic Code: P2.1 (Forces)
Detailed Solution: – Spring B has the smallest extension (0.3 cm) for the same mass, indicating it has the largest spring constant (stiffest spring).
9. (b) (i) Calculate the resistance of the metal spring.
▶️Answer/Explanation
Answer: 2 Ω
Sub-topic Code: P9.1 (Electric Circuits)
Detailed Solution: – Total voltage = 9 V – Voltage across spring = 9 V – 7.5 V = 1.5 V – Resistance = Voltage / Current = 1.5 V / 0.75 A = 2 Ω
9. (b) (ii) Draw on Fig. 9.3 to show the shape and direction of the magnetic field due to the current in the solenoid.
▶️Answer/Explanation
Answer: Correct shape and direction of magnetic field lines
Sub-topic Code: P11.1 (Magnetism)
Detailed Solution: – The magnetic field lines should be drawn as concentric circles around the solenoid, with the direction following the right-hand rule (clockwise or counterclockwise depending on the current direction).
10. (a) (i) State the name of the effect shown by the change in appearance of the cells.
▶️Answer/Explanation
Answer: Plasmolysis
Sub-topic Code: B2.1 (Cell Structure)
Detailed Solution: – Plasmolysis occurs when plant cells lose water and shrink away from the cell wall due to being placed in a hypertonic solution (e.g., concentrated glucose solution).
10. (a) (ii) Explain the process that causes the cells in Fig. 10.1 to change appearance when immersed in concentrated glucose solution.
▶️Answer/Explanation
Answer: Water moves out of the cells by osmosis, causing them to shrink.
Sub-topic Code: B2.1 (Cell Structure)
Detailed Solution: – The concentrated glucose solution has a lower water potential than the cell cytoplasm. – Water moves out of the cells by osmosis, causing the cells to shrink and the cytoplasm to pull away from the cell wall (plasmolysis).
10. (b) State the two main substances transported during translocation.
▶️Answer/Explanation
Answer: Sucrose; amino acids
Sub-topic Code: B6.1 (Transport in Plants)
Detailed Solution: – Translocation is the movement of sucrose and amino acids through the phloem from sources (e.g., leaves) to sinks (e.g., roots, fruits).
11. (a) State one property of diamond that makes it suitable for use in cutting tools.
▶️Answer/Explanation
Answer: Hardness
Sub-topic Code: C16.1 (Properties of Materials)
Detailed Solution: – Diamond is the hardest known natural material, making it ideal for cutting and drilling tools.
11. (b) State a use for graphite.
▶️Answer/Explanation
Answer: Lubricant / pencils / electrodes
Sub-topic Code: C16.1 (Properties of Materials)
Detailed Solution: – Graphite is used as a lubricant due to its slippery nature, in pencils due to its ability to leave marks, and in electrodes due to its electrical conductivity.
11. (c) Explain how graphite conducts electricity.
▶️Answer/Explanation
Answer: Delocalized electrons can move through the structure.
Sub-topic Code: C16.1 (Properties of Materials)
Detailed Solution: – Graphite has a layered structure with delocalized electrons between the layers. These electrons are free to move, allowing graphite to conduct electricity.
11. (d) State the name of the type of bond between carbon atoms in diamond.
▶️Answer/Explanation
Answer: Covalent
Sub-topic Code: C17.1 (Chemical Bonding)
Detailed Solution: – Diamond has a giant covalent structure, where each carbon atom is bonded to four other carbon atoms by strong covalent bonds.
11. (e) Complete the dot-and-cross diagram to show the bonding in carbon dioxide.
▶️Answer/Explanation
Answer: – 11(e)
Carbon dioxide (CO₂) has double bonds between carbon and each oxygen atom. – Each oxygen atom shares two electrons with the carbon atom.
Sub-topic Code: C17.1 (Chemical Bonding)
Detailed Solution: – Carbon dioxide has a linear structure with double bonds between carbon and each oxygen atom. The dot-and-cross diagram should show the sharing of electrons in these double bonds.
12. (a) State the names of the forms of radiation labelled P, Q, and R in Fig. 12.1.
▶️Answer/Explanation
Answer: P: microwaves; Q: infrared; R: ultraviolet
Sub-topic Code: P5.1 (Electromagnetic Spectrum)
Detailed Solution: – P is microwaves, which have longer wavelengths than infrared. – Q is infrared, which is between microwaves and visible light. – R is ultraviolet, which has shorter wavelengths than visible light.
12. (b) Calculate the refractive index of the glass block.
▶️Answer/Explanation
Answer: 1.93
Sub-topic Code: P6.1 (Light)
Detailed Solution: – Refractive index (n) = sin(i) / sin(r) = sin(30°) / sin(15°) ≈ 1.93
12. (c) (i) Draw lines to match each form of ionising radiation with its nature and relative ionising effect.
▶️Answer/Explanation
Answer: – 12(c)(i)
α-particle: helium nucleus, high ionising effect – β-particle: electron, medium ionising effect – γ-ray: electromagnetic radiation, low ionising effect
Sub-topic Code: P12.1 (Radioactivity)
Detailed Solution: – α-particles are helium nuclei and have the highest ionising effect. – β-particles are electrons and have a medium ionising effect. – γ-rays are electromagnetic waves and have the lowest ionising effect.
12. (c) (ii) Complete the decay equation for lead-210.
▶️Answer/Explanation
Answer: \[ ^{210}_{82}Pb \rightarrow ^{210}_{83}Bi + ^{0}_{-1}\beta \]
Sub-topic Code: P12.1 (Radioactivity)
Detailed Solution: – Lead-210 decays by β-decay to form bismuth-210, emitting a β-particle (electron).
12. (c) (iii) Determine the half-life of lead-210 using Fig. 12.3.
▶️Answer/Explanation
Answer: 22 years
Sub-topic Code: P12.1 (Radioactivity)
Detailed Solution: – The half-life is the time taken for the activity to halve. From the graph, the activity decreases from 400 counts/min to 200 counts/min in approximately 22 years.