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Question 1:

1(a)(i) – B15.4 Sexual reproduction in humans

1(a)(ii) – B15.4 Sexual reproduction in humans

1(b)(i) – B15.4 Sexual reproduction in humans

1(b)(ii) – B15.4 Sexual reproduction in humans

1(c)(i) – B12.1 Respiration

1(c)(ii) – B12.1 Respiration

1(d) – B15.4 Sexual reproduction in humans

(a) A student investigates the germination of pea seeds. (Sub-topic – B3.1)

The student places pea seeds in test-tubes with different conditions and records whether the seeds germinate.

Table 1.1 shows the conditions for each test-tube.

Test-tube	water present?	oxygen present?
A	yes	yes
B	yes	no
C	no	no
D	no	yes

(i) Predict in which test-tube the pea seeds will germinate.

▶️Answer/Explanation

Explanation:
Germination requires both water and oxygen. Therefore, the seeds will germinate in test-tube A, where both water and oxygen are present.

(ii) State one other requirement for germination that is not tested in Table 1.1.

▶️Answer/Explanation

suitable temperature

(b) After the seeds germinate, the plant photosynthesizes. (Sub-topic – B6.1)

(i) Complete the sentence to define photosynthesis.

▶️Answer/Explanation

carbohydrates; light

(ii) State the two raw materials needed for photosynthesis.

▶️Answer/Explanation

carbon dioxide; water

State the name of the smaller molecules from which protein is made.

▶️Answer/Explanation

Proteins are made from smaller molecules called amino acids.

Question 2:

2(a) – C11.3 Fuels

2(b) – C11.3 Fuels

2(c) – C11.3 Fuels

2(d)(i) – C11.5 Alkenes

2(d)(ii) – C11.5 Alkenes

2(d)(iii) – C11.5 Alkenes

2(d)(iv) – C11.5 Alkenes

2(d)(v) – C11.5 Alkenes

(a) Petroleum is a fossil fuel.

State the name of one other fossil fuel. (Sub-topic – C11.3)

▶️Answer/Explanation

Coal / natural gas

(b) Petroleum is separated into useful fractions by fractional distillation.

State why fractional distillation is a physical change and not a chemical change. (Sub-topic – C6.1)

▶️Answer/Explanation

Change is reversible / no new products formed

On Fig. 2.1, draw one line from each fraction to its use. One line has been drawn for you. (Sub-topic – C11.3)

Fraction	Use
Bitumen	Road surfaces
Gas oil	Diesel engine fuel
Gasoline	Petrol engine fuel

▶️Answer/Explanation

Bitumen – road surfaces; Gas oil – diesel engine fuel; Gasoline – petrol engine fuel

(d) Ethane and ethene are both found in petroleum. Ethane, \( C_2H_6 \), is an alkane. Ethene, \( C_2H_4 \), is an alkene. (Sub-topic – C11.5)

(i) Explain why ethene is described as being unsaturated.

▶️Answer/Explanation

Contains a carbon-carbon double bond

(ii) State the chemical test used to distinguish between an alkane and an alkene.

Describe the observation for an alkane and for an alkene.

▶️Answer/Explanation

Test: Aqueous bromine

Observation for alkane: No change / stays orange

Observation for alkene: Decolourises

(iii) State the total number of atoms in one molecule of ethene, \( C_2H_4 \).

▶️Answer/Explanation

Six

(iv) Complete Fig. 2.2 to show the structural formula of ethane, \( C_2H_6 \).

▶️Answer/Explanation

H-C-C-H

(v) Ethene molecules react together when heated to make a polymer.

State the name of the polymer made from ethene.

▶️Answer/Explanation

Polyethene / polythene

Question 3:

3(a) – P1.5 Forces

3(b) – P1.2 Motion

3(c)(i) – P5.2 Radioactivity

3(c)(ii) – P5.2 Radioactivity

3(d) – P5.2.4 Half-life

3(e) – P3.2.1 Reflection of light

(a) Fig. 3.1 shows four forces acting on a submarine. The submarine is moving underwater at a constant speed.

State which force A, B, C or D is the weight of the submarine. (Sub-topic – P1.5.1)

▶️Answer/Explanation

Answer: C

Explanation: The weight of the submarine is the force due to gravity acting downward. In the diagram, force C is directed downward, indicating that it represents the weight of the submarine.

(b) The submarine travels 36 km in 2 hours. Calculate the speed of the submarine in m/s. (Sub-topic – P1.2)

▶️Answer/Explanation

Answer: 5 m/s

Explanation:

Convert 36 km to meters: \( 36 \text{ km} = 36,000 \text{ m} \).
Convert 2 hours to seconds: \( 2 \text{ hours} = 2 \times 60 \times 60 = 7,200 \text{ s} \).
Calculate speed using the formula \( \text{speed} = \frac{\text{distance}}{\text{time}} \): \( \text{speed} = \frac{36,000}{7,200} = 5 \text{ m/s} \).

(c) The submarine is powered by a small nuclear reactor. Ionising radiation is released in the reactor. The reactor must be shielded to protect the crew from this radiation. (Sub-topic – P5.2.2)

(i) State how exposure to ionising radiation can affect the human body.

▶️Answer/Explanation

Answer: Cancer / cell mutation

Explanation: Ionising radiation can damage the DNA in cells, leading to mutations that may cause cancer or other harmful effects on the body.

(ii) Suggest a material which can be used to shield a nuclear reactor and stop \(\alpha\)-radiation and \(\beta\)-radiation escaping.

▶️Answer/Explanation

Answer: Lead

Explanation: Lead is a dense material that is effective at blocking \(\alpha\) and \(\beta\) radiation due to its high atomic number and density.

(d) Plutonium-239 (Pu-239) is the nuclear fuel used by the submarine. Pu-239 has a half-life of 24,000 years. A small sample of Pu-239 has a mass of 1.0 g. Calculate the mass of Pu-239 remaining after 96,000 years. (Sub-topic – P5.2.4)

▶️Answer/Explanation

Answer: 0.0625 g

Explanation:

Determine the number of half-lives in 96,000 years: \( \frac{96,000}{24,000} = 4 \) half-lives.
Calculate the remaining mass after each half-life: \( 1.0 \text{ g} \rightarrow 0.5 \text{ g} \rightarrow 0.25 \text{ g} \rightarrow 0.125 \text{ g} \rightarrow 0.0625 \text{ g} \).

(e) When it is under the water, the submarine uses a periscope to view a ship on the surface of the sea. Fig. 3.2 shows a simple periscope.

On Fig. 3.2, draw a ray of light from the ship to the observer’s eye to show what happens to the light ray as it passes through the periscope. (Sub-topic – P3.2.1)

▶️Answer/Explanation

Answer: The light ray should reflect off the top mirror and then the bottom mirror before reaching the observer’s eye.

Explanation: In a periscope, light from the ship enters the top mirror, reflects downward to the bottom mirror, and then reflects into the observer’s eye. The ray should be drawn to show these two reflections.

Question 4 :

4(a)(i) – B3.1 Diffusion

4(a)(ii) – B3.1 Diffusion

4(b) – B3.1 Diffusion

4(c)(i) – B2.1 Cell structure

4(c)(ii) – B12.1 Respiration

4(d) – B2.1 Cell structure

(a) Scientists investigate diffusion by measuring the distance travelled by two different dyes X and Y. They place the dyes on agar plates and measure the distance travelled every 15 seconds. Fig. 4.1 shows the results plotted on a graph. (Sub-topic – B3.1)

(i) Describe the general trend shown by both dyes in Fig. 4.1.

▶️Answer/Explanation

The general trend shown by both dyes is that the distance travelled increases with time. This indicates that diffusion is occurring, and the dyes are spreading out from their original position over time.

(ii) The dyes move through the agar by diffusion. The scientists calculate the average rate of diffusion for dye X after 30 seconds as:

\[ \frac{\text{distance travelled}}{\text{time taken}} = \frac{11}{30} = 0.37 \, \text{mm/s} \]

Calculate the average rate of diffusion for dye Y after 30 seconds.

▶️Answer/Explanation

From the graph, the distance travelled by dye Y after 30 seconds is 6 mm. Therefore, the average rate of diffusion for dye Y is:

\[ \frac{6 \, \text{mm}}{30 \, \text{s}} = 0.2 \, \text{mm/s} \]

(b) Describe the direction of motion of particles during diffusion. (Sub-topic – B3.1)

▶️Answer/Explanation

During diffusion, particles move from a region of higher concentration to a region of lower concentration. This movement occurs due to the random motion of particles, and it continues until the concentration of particles is uniform throughout the medium.

(i) State the part of the cell that controls the movement of substances in and out of the cell.

▶️Answer/Explanation

The cell membrane controls the movement of substances in and out of the cell.

(ii) Circle two substances that diffuse into cells for respiration.

carbon dioxide fatty acids glucose oxygen starch water

▶️Answer/Explanation

The two substances that diffuse into cells for respiration are glucose and oxygen.

(d) Table 4.1 shows some components of plant cells and their function. Complete Table 4.1.

Component of Plant Cell	Function
Vacuole	Contains cell sap to support the plant cell
Cytoplasm	Where chemical reactions occur / contains the cell structures / contains enzymes
Chloroplast	Where photosynthesis occurs

▶️Answer/Explanation

The completed table is as follows:

Component of Plant Cell	Function
Vacuole	Contains cell sap to support the plant cell
Cytoplasm	Where chemical reactions occur / contains the cell structures / contains enzymes
Chloroplast	Where photosynthesis occurs

Question 5:

5(a)(i) – C2.2 Atomic structure and the Periodic Table

5(a)(ii) – C10.1 Water

5(a)(iii) – C6.2 Rate of reaction

5(a)(iv) – C10.2 Air quality and climate

5(a)(v) – C2.5 Simple molecules and covalent bonds

5(b)(i) – C5.1 Exothermic and endothermic reactions

5(b)(ii) – C10.1 Water

5(b)(iii) – C10.1 Water

(a) The list below shows the formulae of six molecules.

CH₄ Cl₂ CO N₂ NH₃ O₂

Identify which of the molecules from the list is:

(i) an ammonia molecule (Topic – C2.2)

▶️Answer/Explanation

NH₃

Explanation: Ammonia is a compound with the chemical formula NH₃, consisting of one nitrogen atom and three hydrogen atoms.

(ii) a molecule used in the treatment of water (Topic – C10.1)

▶️Answer/Explanation

Cl₂

Explanation: Chlorine (Cl₂) is commonly used in water treatment to kill bacteria and other pathogens.

(iii) a molecule formed during the incomplete combustion of carbon-containing substances (Topic – C6.2)

▶️Answer/Explanation

Explanation: Carbon monoxide (CO) is formed during the incomplete combustion of carbon-containing substances when there is insufficient oxygen.

(iv) the molecule of the gas that is 78% of clean dry air (Topic – C10.2)

▶️Answer/Explanation

N₂

Explanation: Nitrogen (N₂) makes up approximately 78% of the Earth’s atmosphere by volume.

(v) a molecule that contains four covalent bonds. (Topic – C2.5)

▶️Answer/Explanation

CH₄

Explanation: Methane (CH₄) contains four covalent bonds, one between the carbon atom and each of the four hydrogen atoms.

(b) Lime (calcium oxide) is made from limestone (calcium carbonate) by thermal decomposition.

(i) State the name of the other product of this reaction. (Topic – C6.1)

▶️Answer/Explanation

Carbon dioxide

Explanation: The thermal decomposition of calcium carbonate (CaCO₃) produces calcium oxide (CaO) and carbon dioxide (CO₂).

(ii) Calcium carbonate is not a fertiliser but is often added to soil. Explain why calcium carbonate is often added to soil. (Topic – C10.1)

▶️Answer/Explanation

To neutralize acidic soil

Explanation: Calcium carbonate is added to soil to neutralize acidity, improving soil pH and making it more suitable for plant growth.

(iii) List the three essential elements needed in a fertiliser. (Topic – C10.1)

▶️Answer/Explanation

1. Nitrogen
2. Phosphorus
3. Potassium

Explanation: These three elements are essential for plant growth and are commonly found in fertilizers to promote healthy development.

Question 6:

6(a) – P3.4 Sound

6(b)(i) – P3.3 Electromagnetic spectrum

6(b)(ii) – P3.3 Electromagnetic spectrum

6(c)(i) – P3.1 General properties of waves

6(c)(ii) – P3.4 Sound

6(c)(iii) – P3.4 Sound

Bats use the reflection of sound waves to determine the position of objects.

Fig. 6.1 shows a bat, and a moth flying in front of the bat.

(a) State the name given to a reflected sound wave. (Topic – P3.4)

▶️Answer/Explanation

Echo

Explanation: An echo is the reflection of sound waves off a surface, which is how bats detect objects in their environment.

(b) Some bats are able to detect ultraviolet radiation. Ultraviolet radiation is part of the electromagnetic spectrum. (Topic – P3.3)

(i) On the incomplete electromagnetic spectrum shown in Fig. 6.2, place ultraviolet in the correct position.

▶️Answer/Explanation

Ultraviolet should be placed between X-rays and infrared.

Explanation: The electromagnetic spectrum is ordered by wavelength and frequency. Ultraviolet (UV) radiation has a shorter wavelength and higher frequency than visible light but longer wavelength and lower frequency than X-rays.

(ii) State which part of the electromagnetic spectrum has the lowest frequency.

▶️Answer/Explanation

Radio waves

Explanation: Radio waves have the longest wavelength and the lowest frequency in the electromagnetic spectrum.

(i) Draw straight lines to link each wave term to its definition. (Topic – P3.1)

▶️Answer/Explanation

Amplitude – Maximum displacement of points on a wave
Frequency – Number of waves passing a fixed point per second
Wavelength – Distance between the peaks on consecutive waves

Explanation: Amplitude is the height of the wave, frequency is how often the wave passes a point, and wavelength is the distance between two consecutive peaks or troughs.

(ii) Explain why a human cannot hear the sound emitted by the bat. (Topic – P3.4)

▶️Answer/Explanation

Humans cannot hear sounds with frequencies above 20 kHz.

Explanation: The human hearing range is typically between 20 Hz and 20 kHz. The bat’s sound wave has a frequency of 200 kHz, which is well above the upper limit of human hearing.

(iii) The bat changes the frequency of the sound it produces from 200 kHz to 250 kHz. State what happens to the pitch of the sound. (Topic – P3.4)

▶️Answer/Explanation

The pitch increases.

Explanation: Pitch is directly related to frequency. As the frequency increases from 200 kHz to 250 kHz, the pitch of the sound also increases.

Question 7:

7(a)(i) – B17.1 Variation

7(a)(ii) – B17.1 Variation

7(a)(iii) – B17.1 Variation

7(a)(iv) – B17.1 Variation

7(b)(i) – B16.1 Chromosomes and genes

7(b)(ii) – B16.1 Chromosomes and genes

7(c) – B16.1 Chromosomes and genes

(a) Students in a school measure their hand-span. (Topic: B17)

Fig. 7.1 is a photograph showing the measurement that each student takes.

Fig. 7.2 is a histogram showing the results.

(i) Determine which hand-span category has the most students. (Sub-topic: B17.1)

▶️Answer/Explanation

The hand-span category with the most students is 22.0–22.9 cm.

(ii) Determine the number of students with a hand-span of 19.0–19.9 cm. (Sub-topic: B17.1)

▶️Answer/Explanation

The number of students with a hand-span of 19.0–19.9 cm is 4.

(iii) Histograms are used to display data that show continuous variation. What other evidence from Fig. 7.2 shows that hand-span is an example of continuous variation? (Sub-topic: B17.1)

▶️Answer/Explanation

Hand-span is an example of continuous variation because there is a range of values between two extremes, rather than distinct separate categories.

(iv) State the name of one other example of continuous variation. (Sub-topic: B17.1)

▶️Answer/Explanation

One other example of continuous variation is height.

7 (b) Fig. 7.3 is an incomplete Punnett square, genetic diagram. (Topic: B16)

(i) Complete Fig. 7.3 to show how sex is inherited in humans. (Sub-topic: B16.2)

▶️Answer/Explanation

The completed Punnett square should be:

	X	Y
X	XX (Female)	XY (Male)
X	XX (Female)	XY (Male)

This shows that there is a 50% chance of having a male or female offspring.

(ii) Use Fig. 7.3 to determine the ratio of male offspring to female offspring. (Sub-topic: B16.2)

▶️Answer/Explanation

The ratio of male offspring to female offspring is 1:1.

7 (c) Several structures are involved in inheritance. (Topic: B16)

chromosomes, DNA, gene, nucleus

Place structures from the list in order of size from smallest to largest. (Sub-topic: B16.1)

▶️Answer/Explanation

The correct order from smallest to largest is:

DNA
Gene
Chromosome
Nucleus

Question 8:

8(a) – C8.1 Arrangement of elements

8(b) – C2.4 Ions and ionic bonds

8(c)(i) – C4.1 Electrolysis

8(c)(ii) – C4.1 Electrolysis

8(c)(iii) – C4.1 Electrolysis

(a) Potassium is an element in the Periodic Table. (Topic: C8)

Use numbers from the list to complete the sentences about potassium.
Each number may be used once, more than once, or not at all.

1 2 3 8 19 20 39

(i) Potassium is an element in group … of the Periodic Table. (Sub-topic: C8.1)

▶️Answer/Explanation

Potassium is an element in Group 1 of the Periodic Table because it is an alkali metal.

(ii) A potassium atom has a total of … electrons. (Sub-topic: C8.1)

▶️Answer/Explanation

A potassium atom has a total of 19 electrons because its atomic number is 19.

(iii) A potassium ion has a positive charge of …. (Sub-topic: C8.2)

▶️Answer/Explanation

A potassium ion has a positive charge of 1 because it loses one electron to form K⁺.

(b) Sodium and chlorine react to form sodium chloride. (Topic: C8)

Fig. 8.1 shows the electronic structure of a sodium atom and a chlorine atom.

(i) Complete the diagrams in Fig. 8.2 to show the electronic structure of the ions in sodium chloride. (Sub-topic: C8.2)

▶️Answer/Explanation

Sodium ion (Na⁺): 2,8 (lost one electron)
Chloride ion (Cl⁻): 2,8,8 (gained one electron)
This transfer of electrons forms an ionic bond.

(i) Complete Fig. 8.3 by labelling the: (Sub-topic: C4.2)

Anode
Cathode
Electrolyte

▶️Answer/Explanation

Anode (Positive Electrode): Where oxidation occurs
Cathode (Negative Electrode): Where reduction occurs
Electrolyte: Concentrated aqueous sodium chloride (NaCl solution).

(ii) Hydrogen gas is one of the electrode products of this electrolysis. State the name of the other electrode product. (Sub-topic: C4.2)

▶️Answer/Explanation

The other electrode product is chlorine gas (Cl₂), which is released at the anode.

(iii) Describe the chemical test for hydrogen gas. State the observation for a positive result. (Sub-topic: C4.3)

▶️Answer/Explanation

Test: Hold a lighted splint near the gas.
Observation: If hydrogen gas is present, it will produce a ‘pop’ sound as it burns.

Question 9:

9(a) – P1.3 Mass and weight

9(b)(i) – P1.5 Forces

9(b)(ii) – P1.5 Forces

9(c)(i) – P1.6.1 Energy

9(c)(ii) – P4.2.4 Resistance

9(c)(iii) – P4.4 Electrical safety

Fig. 9.1 shows an aircraft at rest on a runway.

(a) The mass of the aircraft is 400 000 kg.

Calculate the weight of the aircraft. The gravitational field strength, \( g \), is 10 N/kg. (Topic – P1.3)

▶️Answer/Explanation

Weight = 4,000,000 N

Explanation: Weight is calculated using the formula \( W = m \times g \), where \( m \) is mass and \( g \) is gravitational field strength. Substituting the values, \( W = 400,000 \, \text{kg} \times 10 \, \text{N/kg} = 4,000,000 \, \text{N} \).

(b) The aircraft starts from rest and accelerates along the straight runway. The aircraft engines produce a constant horizontal thrust force of 1,200,000 N. A constant frictional force of 500,000 N acts on the aircraft. (Topic – P1.5)

(i) Calculate the resultant horizontal force acting on the aircraft.

▶️Answer/Explanation

Resultant force = 700,000 N

Explanation: The resultant force is calculated by subtracting the frictional force from the thrust force: \( F_{\text{resultant}} = 1,200,000 \, \text{N} – 500,000 \, \text{N} = 700,000 \, \text{N} \).

(ii) Explain why the aircraft accelerates.

▶️Answer/Explanation

The aircraft accelerates because there is a resultant force acting on it.

Explanation: According to Newton’s Second Law of Motion, an object accelerates when there is a resultant force acting on it. In this case, the resultant force of 700,000 N causes the aircraft to accelerate.

(i) The number of joules of sound energy transferred per second is shown as XJ. Calculate the value of X. (Topic – P1.6)

▶️Answer/Explanation

X = 1 J

Explanation: The total energy input is 200 J, and the energy outputs are 119 J (light) and 80 J (thermal). Therefore, the sound energy \( X = 200 \, \text{J} – (119 \, \text{J} + 80 \, \text{J}) = 1 \, \text{J} \).

(ii) The monitor has a resistance of 1900 Ω. The current passing through the monitor when in use is 0.060 A.

Calculate the potential difference across the monitor. State the unit of your answer. (Topic – P4.2)

▶️Answer/Explanation

Potential difference = 114 V

Explanation: The potential difference (V) is calculated using Ohm’s Law: \( V = I \times R \). Substituting the values, \( V = 0.060 \, \text{A} \times 1900 \, \Omega = 114 \, \text{V} \).

(iii) The current of 0.060 A is the same as 60 mA. The fuse in the electrical supply to the monitor has to be replaced. Several fuse ratings are available.

10 mA 50 mA 100 mA 250 mA

State which fuse is the correct choice. Explain your answer. (Topic – P4.4)

▶️Answer/Explanation

Fuse = 100 mA

Explanation: The fuse rating should be higher than the maximum current (60 mA) but not too much higher to ensure safety. A 100 mA fuse is the most appropriate choice as it is the smallest value above 60 mA.

Question 10:

10(a)(i) – B7.2 Digestive system

10(a)(ii) – B7.2 Digestive system

10(b) – B7.2 Digestive system

10(c) – B7.2 Digestive system

(a) Fig. 10.1 is a diagram of the alimentary canal and associated organs in a human. (Sub-topic – B7.2)

(i) Identify the letter in Fig. 10.1 that represents the part where:

ingestion occurs – K
egestion occurs – F
mechanical digestion occurs – K or C
saliva is produced – A

▶️Answer/Explanation

K; F; K/C; A

(ii) State the name of the parts labelled D and H in Fig. 10.1.

D – pancreas
H – gall bladder

▶️Answer/Explanation

D – pancreas; H – gall bladder

(b) Table 10.1 shows some features of absorption and assimilation.

Place ticks (✓) in the boxes to show the features of each process. (Sub-topic – B7.2)

process	feature
process	movement of digested food molecules	movement into blood	movement into cells
absorption
assimilation

▶️Answer/Explanation

Here is the completed table with ticks (✓):

process	feature
process	movement of digested food molecules	movement into blood	movement into cells
absorption	✓	✓
assimilation	✓		✓

One has been done for you.

carbohydrates – main source of energy
fibre – prevents constipation
iron – needed for haemoglobin
protein – for growth and repair of tissues
vitamin D – needed for bone growth

▶️Answer/Explanation

carbohydrates – main source of energy; fibre – prevents constipation; iron – needed for haemoglobin; protein – for growth and repair of tissues; vitamin D – needed for bone growth

Question 11:

11(a)(i) – C7.3 Preparation of salts

11(a)(ii) – C7.3 Preparation of salts

11(a)(iii) – C2.5 Simple molecules and covalent bonds

11(a)(iv) – C5.1 Exothermic and endothermic reactions

11(a)(v) – C6.2 Rate of reaction

11(b) – C8.4 Transition elements

11(c)(i) – C9.3 Alloys and their properties

11(c)(ii) – C9.3 Alloys and their properties

Fig. 11.1 shows the apparatus and reagents used to make a salt.

(a) (i) State the name of process A shown in Fig. 11.1. (Sub-topic – C7.3)

▶️Answer/Explanation

filtration

Explanation: Process A is filtration, which is used to separate solid particles from a liquid.

(ii) State the name of the salt made in this experiment. (Sub-topic – C7.3)

▶️Answer/Explanation

copper sulfate

Explanation: The salt made in this experiment is copper sulfate.

(iii) Carbon dioxide gas is also made.

Explain why the bonds between the carbon atoms and the oxygen atoms in carbon dioxide are covalent. (Sub-topic – C2.5)

▶️Answer/Explanation

two non-metals bonding / electrons are shared

Explanation: The bonds between carbon and oxygen in carbon dioxide are covalent because they involve the sharing of electrons between the carbon and oxygen atoms. Carbon dioxide is a molecule formed by two non-metals (carbon and oxygen), and non-metals typically form covalent bonds by sharing electrons to achieve a stable electron configuration.

(iv) The temperature of the reacting mixture increases during the reaction.

State the name given to all chemical reactions that release heat. (Sub-topic – C5.1)

▶️Answer/Explanation

exothermic

Explanation: Chemical reactions that release heat are called exothermic reactions.

(v) The experiment is repeated using large pieces of copper carbonate instead of powdered copper carbonate.

State what happens to the rate of reaction. (Sub-topic – C6.2)

▶️Answer/Explanation

(rate of reaction) decreases

Explanation: Using large pieces of copper carbonate instead of powdered copper carbonate decreases the rate of reaction. This is because the surface area of the reactant is reduced, leading to fewer collisions between reactant particles per unit time.

(b) Copper carbonate is green. Copper is a transition metal.

State two other properties of transition metals which are not properties of all metals. (Sub-topic – C8.4)

▶️Answer/Explanation

1. high density; 2. catalyst; 3. variable valency (any two)

Explanation:

Two other properties of transition metals are:

They form colored compounds.
They can act as catalysts in chemical reactions.

(i) State the name given to a mixture of metals. (Sub-topic – C9.3)

▶️Answer/Explanation

alloy

Explanation: A mixture of metals is called an alloy.

(ii) State one advantage of brass compared to copper. (Sub-topic – C9.3)

▶️Answer/Explanation

stronger / any valid point

Explanation: One advantage of brass compared to copper is that it is stronger and more resistant to corrosion.

Question 12:

12(a) – P3.2.1 Reflection of light

12(b)(i) – P1.2 Motion

12(b)(ii) – P1.6.1 Energy

12(b)(iii) – P1.2 Motion

12(c)(i) – P1.4 Density

12(c)(ii) – C12.5 Identification of ions and gases

12(d)(i) – P2.3 Transfer of thermal energy

12(d)(ii) – P2.2.2 Melting, boiling and evaporation

12(d)(iii) – P2.1.2 Particle model

An astronomer observes a large meteorite, a rock from outer space. The astronomer uses a telescope which contains mirrors.

Fig. 12.1 shows the image of the meteorite seen in the mirror by the astronomer.

(a) Select two words or phrases from the list to describe the characteristics of an image formed by a single plane mirror. (Sub-topic – P3.2.1)

▶️Answer/Explanation

The two characteristics of an image formed by a single plane mirror are:

same size
upright

(b) The meteorite enters the Earth’s atmosphere.

Fig. 12.2 is a speed-time graph for the meteorite as it approaches Earth.

(i) On Fig. 12.2, label with an S a point when the meteorite is slowing down. (Sub-topic – P1.2)

▶️Answer/Explanation

The meteorite slows down when it experiences air resistance, which occurs after it reaches its maximum speed. Label a point on the graph where the speed starts to decrease.

S somewhere between 5 s and 12 s

(ii) State the form of energy lost by the meteorite as it slows down. (Sub-topic – P1.6.1)

▶️Answer/Explanation

The meteorite loses kinetic energy as it slows down due to air resistance and friction with the atmosphere.

(iii) Use Fig. 12.2 to determine the maximum speed of the meteorite. (Sub-topic – P1.2)

▶️Answer/Explanation

The maximum speed of the meteorite is 36,000 m/s, as indicated by the highest point on the speed-time graph.

(i) Calculate the volume of the meteorite. (Sub-topic – P1.4)

▶️Answer/Explanation

Using the formula: Volume = Mass ÷ Density,

Volume = 22,500 kg ÷ 7500 kg/m³ = 3.0 m³.

(ii) A scientist suggests that the meteorite contains metallic iron.

Suggest a simple way for the scientist to test for iron in an object found on Earth. (Sub-topic – C12.5)

▶️Answer/Explanation

The scientist can use a magnet to test for the presence of iron. If the object is attracted to the magnet, it likely contains iron.

(d) The meteorite’s temperature is 1500°C when it falls into the sea. The meteorite loses thermal energy to the water.

(i) State the main method of thermal energy transfer from the meteorite into the water. (Sub-topic – P2.3.1)

▶️Answer/Explanation

The main method of thermal energy transfer from the meteorite into the water is conduction, as the heat is transferred through direct contact between the meteorite and the water.

(ii) Some of the seawater evaporates.

Describe the process of evaporation in terms of the movement and energy of water molecules. (Sub-topic – P2.2.2)

▶️Answer/Explanation

Evaporation occurs when the most energetic water molecules at the surface gain enough energy to escape into the air as gas. This process cools the remaining liquid as the higher-energy molecules leave.

(iii) The meteorite is a solid and the seawater is a liquid.

Draw more circles in the boxes in Fig. 12.3 to show the arrangement and separation of particles in a solid and in a liquid. (Sub-topic – P2.1.1)

▶️Answer/Explanation

In a solid, particles are closely packed in a regular arrangement. In a liquid, particles are close together but not in a fixed arrangement, allowing them to move past each other.

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