Question 1
(a) Fig. 1.1 is a diagram of the human female reproductive system. (Sub-topic: B15.4)
(i) Label Fig. 1.1 using words from the list. Each word may be used once, more than once or not at all.
cervix ovary oviduct uterus vagina
▶️Answer/Explanation
The labels should be as follows:
- Bottom left: Ovary
- Middle left: Oviduct
- Top center: Uterus
- Bottom center: Cervix
- Bottom right: Vagina
(ii) The boxes on the left are parts of the human female reproductive system. The boxes on the right are the functions of the different parts. Draw one line from each part to its function. (Sub-topic: B15.4)
▶️Answer/Explanation
The correct matches are:
- Ovary → Releases female gametes
- Oviduct → Site of fertilisation
- Uterus → Where fetus develops
- Vagina → Receives penis during sexual intercourse
(b) HIV is a sexually transmitted disease often spread through unprotected sexual intercourse. Fig. 1.2 is a graph showing the number of new infections of HIV in a country between 1999 and 2009.
(i) Calculate the overall change in the number of new HIV infections between 1999 and 2009. (Sub-topic: B15.5)
▶️Answer/Explanation
The overall change in the number of new HIV infections between 1999 and 2009 is calculated as follows:
- Number of new infections in 1999: 3100
- Number of new infections in 2009: 4500
- Change = 4500 – 3100 = 1400
Therefore, the overall change is 1400.
(ii) Describe the trends in new HIV infections between 1999 and 2009. Use data to support your answer. (Sub-topic: B15.5)
▶️Answer/Explanation
The trends in new HIV infections between 1999 and 2009 are as follows:
- The number of new HIV infections increased from 1999 to 2002, peaking at 7000 new infections in 2002.
- After 2002, the number of new infections decreased steadily until 2009, reaching 4500 new infections.
This indicates an initial rise in infections followed by a significant decline.
(c) Table 1.1 shows methods of how HIV can be transmitted or controlled. Complete Table 1.1 to identify if the method is an example of transmission or control. (Sub-topic: B15.5)
▶️Answer/Explanation
The completed table is as follows:
- Barrier contraception → Control
- Contaminated blood transfusion → Transmission
- Sharing needles when taking drugs → Transmission
Question 2 (Sub-topic: P1.2)
(a) The diagram in Fig. 2.1 shows part of the water cycle.
Clouds form above the sea and rain falls from the clouds. Clouds are made up of very small drops of liquid water.
The letters P, Q, and R show locations where physical changes happen in the water cycle.
(i) Use the letters P, Q, and R to complete Table 2.1.
Each letter may be used once, more than once, or not at all.
| Description of change | Location |
|---|---|
| Water vapour condenses | |
| Liquid water gains kinetic energy | |
| Water molecules move closer together | |
| Water evaporates |
▶️Answer/Explanation
Answer:
| Description of change | Location |
|---|---|
| Water vapour condenses | Q |
| Liquid water gains kinetic energy | R |
| Water molecules move closer together | Q |
| Water evaporates | P |
Explanation:
– Water vapour condenses at location Q, where the water vapour in the clouds turns into liquid water.
– Liquid water gains kinetic energy at location R, where the water is heated and gains energy to evaporate.
– Water molecules move closer together at location Q, where condensation occurs, causing the molecules to come closer.
– Water evaporates at location P, where the liquid water turns into water vapour due to heat energy.
(ii) Explain why the changes P, Q, and R are physical changes.
▶️Answer/Explanation
Answer:
The changes P, Q, and R are physical changes because they involve changes in the state of water (solid, liquid, gas) without altering the chemical composition of the water molecules. In physical changes, no new substances are formed, and the process is reversible. Explanation:
– Evaporation (P): Water changes from liquid to gas, but the chemical structure of H2O remains the same.
– Condensation (Q): Water changes from gas to liquid, but the chemical structure remains unchanged.
– Gaining kinetic energy (R): The water molecules gain energy, but the chemical composition of the water remains the same.
(b) Carbon dioxide in the air dissolves in rainwater. This causes the rainwater to become slightly acidic.
(i) Water is neutral. State the pH value of water.
▶️Answer/Explanation
Answer:
The pH value of water is 7. Explanation:
Water is considered neutral because it has a pH of 7, which is neither acidic nor basic.
(ii) Suggest a pH value of rainwater.
▶️Answer/Explanation
Answer:
The pH value of rainwater is less than 7, typically around 5.6. Explanation:
Rainwater becomes slightly acidic due to the dissolution of carbon dioxide, forming carbonic acid, which lowers the pH below 7.
(c) Complete the word equation for the neutralisation reaction between an acid and a base.
acid + base → ________ + ________
▶️Answer/Explanation
Answer:
acid + base → salt + water Explanation:
In a neutralisation reaction, an acid reacts with a base to produce a salt and water.
(d) Table 2.2 shows some oxides. It also shows whether they are acidic or basic.
| Oxide | Acidic or Basic |
|---|---|
| Carbon dioxide | Acidic |
| Chlorine oxide | Acidic |
| Magnesium oxide | Basic |
| Phosphorus oxide | Acidic |
| Sodium oxide | Basic |
(i) Predict whether nitrogen dioxide is acidic or basic. Explain your answer.
▶️Answer/Explanation
Answer:
Nitrogen dioxide is acidic. Explanation:
Nitrogen dioxide is a non-metal oxide, and non-metal oxides are generally acidic. When dissolved in water, nitrogen dioxide forms nitric acid, which is acidic.
(ii) Nitrogen dioxide is an air pollutant. Describe one human activity that releases nitrogen dioxide into the air.
▶️Answer/Explanation
Answer:
Burning of fossil fuels in car engines releases nitrogen dioxide into the air. Explanation:
When fossil fuels are burned in car engines, nitrogen in the air reacts with oxygen at high temperatures to form nitrogen dioxide, which is then released into the atmosphere.
(iii) Identify one other gaseous air pollutant that is harmful to humans.
▶️Answer/Explanation
Answer:
Carbon monoxide (CO) is another gaseous air pollutant that is harmful to humans. Explanation:
Carbon monoxide is a toxic gas that can interfere with the blood’s ability to carry oxygen, leading to health problems such as headaches, dizziness, and even death in high concentrations.
Question 3 (Sub-topic: P1.2)
(a) Fig. 3.1 shows a skier at the top of a slope.
(i) A skier travels 310.5 m in 20 s. Calculate the average speed of the skier.
▶️Answer/Explanation
Solution:
Average speed is calculated using the formula:
\[ \text{Average speed} = \frac{\text{Total distance}}{\text{Total time}} \]
Given:
Total distance = 310.5 m
Total time = 20 s
\[ \text{Average speed} = \frac{310.5}{20} = 15.525 \, \text{m/s} \]
Therefore, the average speed of the skier is 15.5 m/s (rounded to one decimal place).
Answer: 15.5 m/s
(ii) Fig. 3.2 shows a speed-time graph of the skier.
Use Fig. 3.2 to determine the distance travelled while the skier has constant acceleration during the first 8 seconds.
▶️Answer/Explanation
Solution:
To find the distance travelled during constant acceleration, we calculate the area under the speed-time graph for the first 8 seconds. The area under the graph represents the distance travelled.
From the graph, the speed increases linearly from 0 m/s to 23 m/s in 8 seconds. The shape under the graph is a triangle, so the area is:
\[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} \]
Here, the base is 8 seconds, and the height is 23 m/s.
\[ \text{Area} = \frac{1}{2} \times 8 \times 23 = 92 \, \text{m} \]
Therefore, the distance travelled during the first 8 seconds is 92 m.
Answer: 92 m
(iii) State the name of the force that impedes the skier’s motion.
▶️Answer/Explanation
Solution:
The force that impedes the skier’s motion is friction. Friction acts opposite to the direction of motion, slowing the skier down.
Answer: Friction
(b)(i) The skier has a mass of 85 kg. The gravitational field strength \( g \) is 10 N/kg. Calculate the weight of the skier.
▶️Answer/Explanation
Solution:
Weight is calculated using the formula:
\[ \text{Weight} = \text{mass} \times \text{gravitational field strength} \]
Given:
Mass = 85 kg
Gravitational field strength \( g = 10 \, \text{N/kg} \)
\[ \text{Weight} = 85 \times 10 = 850 \, \text{N} \]
Therefore, the weight of the skier is 850 N.
Answer: 850 N
(ii) State the source of the gravitational field that causes the skier to accelerate down a slope.
▶️Answer/Explanation
Solution:
The source of the gravitational field that causes the skier to accelerate down a slope is the Earth. The Earth’s gravitational field exerts a force on the skier, causing acceleration.
Answer: The Earth
(iii) When the skier goes to the top of a slope, he does work. As he climbs, his gravitational potential energy increases. Choose from the list the correct word to complete the sentence below:
created gained lost transferred
The work done by the skier is equal to the total energy ________.
▶️Answer/Explanation
Solution:
The correct word to complete the sentence is transferred. The work done by the skier is equal to the total energy transferred to increase his gravitational potential energy.
Answer: transferred
Question 4 (Sub-topic: B6.1)
A student investigates photosynthesis using an aquatic plant (Elodea).
Fig. 4.1 shows the apparatus the student uses.
(a)(i) The aquatic plant releases bubbles of gas.
Name the gas the bubbles are made from.
▶️Answer/Explanation
Answer: Oxygen
Explanation: During photosynthesis, plants release oxygen as a by-product. The bubbles observed are oxygen gas being released from the plant.
(ii) The investigation was repeated with the filament lamp removed.
Explain why the number of bubbles produced decreases.
▶️Answer/Explanation
Answer: Light is needed for photosynthesis.
Explanation: Photosynthesis requires light energy to convert carbon dioxide and water into glucose and oxygen. Without light, the rate of photosynthesis decreases, leading to fewer bubbles (oxygen) being produced.
(b) Photosynthesis is an enzyme-controlled reaction.
(i) Define the term enzyme.
▶️Answer/Explanation
Answer: An enzyme is a protein that acts as a biological catalyst, speeding up chemical reactions without being consumed in the process.
Explanation: Enzymes are crucial for metabolic processes, including photosynthesis, as they lower the activation energy required for reactions to occur.
(ii) Suggest why placing a hot filament lamp too close to the water could stop the plant producing bubbles.
▶️Answer/Explanation
Answer: Enzymes stop working / enzyme activity slows down.
Explanation: Enzymes have an optimal temperature range. If the temperature becomes too high, enzymes can denature, losing their structure and function, which would halt photosynthesis and the production of oxygen bubbles.
(c) Fig. 4.2 is a photomicrograph of the cells in an Elodea leaf.
(i) Identify the part of the cell labelled X in Fig. 4.2.
▶️Answer/Explanation
Answer: Chloroplast
Explanation: Chloroplasts are the organelles in plant cells where photosynthesis occurs. They contain chlorophyll, which captures light energy.
(ii) Name three parts of a cell found in both plant cells and animal cells.
▶️Answer/Explanation
Answer: Cell membrane, cytoplasm, nucleus
Explanation: Both plant and animal cells share these basic structures. The cell membrane controls the movement of substances in and out of the cell, the cytoplasm is where most cellular activities occur, and the nucleus contains genetic material.
(iii) Suggest two ways the structure of root hair cells would differ from the cells shown in Fig. 4.2.
▶️Answer/Explanation
Answer: Elongated shape, contains no chloroplasts
Explanation: Root hair cells are adapted for absorption, so they have an elongated shape to increase surface area. They do not contain chloroplasts because they are not involved in photosynthesis.
(iv) State one function of root hair cells.
▶️Answer/Explanation
Answer: Absorb water and mineral ions
Explanation: Root hair cells are specialized for absorbing water and nutrients from the soil, which are then transported to other parts of the plant.
Question 5
Non-metallic elements are placed in groups towards the right-hand side of the Periodic Table.
(a) Describe what is meant by a group in the Periodic Table. (Sub-topic: C8.1)
▶️Answer/Explanation
A group in the Periodic Table is a vertical column of elements that have the same number of electrons in their outer shell, leading to similar chemical properties.
(b)(i) Fig. 5.1 shows the chemical symbols of five non-metallic elements.
One of the symbols in Fig. 5.1 is not in the same period of the Periodic Table as the others. Identify the symbol and explain your answer. (Sub-topic: C8.1)
▶️Answer/Explanation
The symbol N (Nitrogen) is not in the same period as the others. The other elements (Cl, Ar, P, S) are in Period 3, while Nitrogen is in Period 2.
(ii) Select two elements from Fig. 5.1 that are contained in fertilisers. (Sub-topic: C10.1)
▶️Answer/Explanation
Nitrogen (N) and Phosphorus (P) are elements commonly found in fertilisers.
(iii) State one reason why fertiliser is added to soil. (Sub-topic: C10.1)
▶️Answer/Explanation
Fertiliser is added to soil to replenish nutrients that are essential for plant growth, such as nitrogen, phosphorus, and potassium.
(c) Select one element from Fig. 5.1 that is used to treat water to make it safe to drink. Explain how it does this. (Sub-topic: C10.1)
▶️Answer/Explanation
Chlorine (Cl) is used to treat water. It kills harmful microorganisms in the water, making it safe to drink by disinfecting it.
(d) Fig. 5.2 shows the electronic structures of atoms of argon, chlorine and potassium.
(i) Argon does not react with potassium. Explain why. Use ideas about electronic structures in your answer. (Sub-topic: C2.2)
▶️Answer/Explanation
Argon has a full outer shell of electrons, making it stable and unreactive. Potassium, on the other hand, has one electron in its outer shell and tends to lose it to achieve stability, but since argon is already stable, it does not react with potassium.
(ii) Potassium reacts with chlorine to form potassium chloride. Describe how the electronic structures of a potassium atom and of a chlorine atom change when potassium and chlorine react. (Sub-topic: C2.4)
▶️Answer/Explanation
Potassium loses one electron from its outer shell, becoming a positively charged ion (K⁺). Chlorine gains one electron, filling its outer shell and becoming a negatively charged ion (Cl⁻). The oppositely charged ions are then attracted to each other, forming an ionic bond in potassium chloride (KCl).
(iii) Name the type of chemical bonding in potassium chloride. (Sub-topic: C2.4)
▶️Answer/Explanation
The type of chemical bonding in potassium chloride is ionic bonding.
Question 6
(a) Solar cells can be used to generate electricity for a house. State one advantage and one disadvantage, apart from cost, of solar cells. (Sub-topic: P1.6.3)
▶️Answer/Explanation
Advantage: Solar cells provide a renewable source of energy, which means they do not deplete natural resources and can be used indefinitely as long as sunlight is available.
Disadvantage: Solar cells cannot produce electricity when it is dark, which limits their effectiveness during nighttime or in areas with limited sunlight.
(b) Fig. 6.1 shows an ice cube and a thermometer in a glass of water.
(i) The water provides thermal energy which melts the ice.
State what happens to the temperature of the ice as it is melting. (Sub-topic: P2.2.2)
▶️Answer/Explanation
The temperature of the ice remains constant at 0°C while it is melting. This is because the thermal energy provided by the water is used to break the bonds between the ice molecules, rather than increasing the temperature.
(ii) Fig. 6.2 shows that more ice cubes have been added to the glass of water.
The ice cubes reduce the temperature of the water. The scale on the liquid-in-glass thermometer shows this decrease in temperature. Explain this action of the liquid-in-glass thermometer. Use ideas about particles in your answer. (Sub-topic: P2.1.2)
▶️Answer/Explanation
The liquid-in-glass thermometer works by the expansion or contraction of the liquid (usually mercury or alcohol) inside it. When the temperature decreases, the particles in the liquid lose kinetic energy and move closer together, causing the liquid to contract. This contraction is observed as a decrease in the level of the liquid in the thermometer, indicating a lower temperature.
(iii) The water in the glass is evaporating. Describe evaporation in terms of the motion of the water molecules. (Sub-topic: P2.2.2)
▶️Answer/Explanation
Evaporation is the process by which water molecules at the surface of the liquid gain enough kinetic energy to escape into the air as gas. The molecules with higher kinetic energy are more likely to escape, leaving behind the molecules with lower kinetic energy, which results in a cooling effect on the remaining liquid.
Question 7
(a) A teacher measured the height of the students in a class to the nearest cm.
Table 7.1 shows the results. (Sub-topic: B17.1)
| height range/cm | frequency in class |
|---|---|
| 140–145 | 2 |
| 146–150 | 6 |
| 151–155 | 8 |
| 156–160 | 12 |
| 161–165 | 5 |
| 166–170 | 2 |
| 171–175 | 1 |
(i) State the most common height range in the class.
▶️Answer/Explanation
Answer: 156–160 cm
(ii) State the type of variation shown by height.
▶️Answer/Explanation
Answer: Continuous
(iii) State the evidence from Table 7.1 that supports your answer in (a)(ii).
▶️Answer/Explanation
Answer: Height is a range (between two extremes) / not distinct categories.
(b) Use words from the list to complete the sentences about natural selection. Each word may be used once, more than once or not at all. (Sub-topic: B17.2)
alleles cells competition
die react survive variety
Individuals in a population produce offspring. If there are not enough resources for all the individuals there is increased …………….. . Individuals that are better adapted to the environment …………….. . Individuals that are not adapted …………….. . Individuals that …………….. can reproduce passing their alleles to the next generation.
▶️Answer/Explanation
Answer: competition, survive, die, survive
(c) Lack of resources can cause extinction of a species. Suggest two ways humans can cause extinction. (Sub-topic: B19.1)
▶️Answer/Explanation
Answer: Any two from: pollution, hunting, deforestation, introducing new diseases, introducing new (competitive) species.
Question 8
Calcium and copper are metals.
(a)(i) State two physical properties of metals. (Sub-topic: C9.1)
▶️Answer/Explanation
1. Good electrical conductor
2. Good thermal conductor
(ii) Copper is a transition metal. Calcium is not a transition metal. State two properties of transition metals that are not properties of calcium. (Sub-topic: C8.4)
▶️Answer/Explanation
1. Forms coloured compounds
2. Can act as a catalyst
(iii) Calcium and copper are added to separate amounts of water. Describe the reaction, if any, for each metal. (Sub-topic: C9.2)
▶️Answer/Explanation
Calcium: Gas evolved, metal dissolves, white insoluble solid forms.
Copper: No change.
(b) Copper metal is produced when copper(II) oxide reacts with hydrogen gas. The equation for this reaction is shown.
CuO + H₂ → Cu + H₂O
(i) Explain why this equation is described as balanced. (Sub-topic: C3.1)
▶️Answer/Explanation
The equation is balanced because the number of atoms of each element is the same on both sides of the equation.
(ii) Identify which substance is reduced in this reaction. Explain your answer. (Sub-topic: C6.3)
▶️Answer/Explanation
Substance: CuO
Explanation: CuO loses oxygen, which is a reduction reaction.
(c) Metals are covered with a thin layer of copper during electroplating. Fig. 8.1 shows apparatus and materials to electroplate a metal key with copper.
Draw a diagram to show the apparatus and materials set up to electroplate the metal key with copper. (Sub-topic: C4.1)
▶️Answer/Explanation
Key and copper electrode connected and dipping into the solution; correct polarity.
Question 9
(a) Fig. 9.1 shows a thin converging lens used in a digital camera. A ray of light has been drawn from a man’s head to the image sensor. (Sub-topic: P3.2.3)
(i) On Fig. 9.1, draw a ray of light from the man’s hand to show where it will be detected on the image sensor of the camera.
▶️Answer/Explanation
Answer: The ray should be drawn parallel to the principal axis from the hand, passing through the focal point on the other side of the lens, and then to the image sensor.
(ii) The image is formed on the image sensor. Circle the two correct words or phrases that describe the image.
diminished enlarged inverted same size upright
▶️Answer/Explanation
Answer: The correct words are diminished and inverted.
(iii) The camera detects visible light and has an infrared sensor. Write visible light and infrared in the correct positions in the electromagnetic spectrum in Fig. 9.2.
▶️Answer/Explanation
Answer: Visible light should be placed between ultraviolet and infrared. Infrared should be placed after visible light and before microwaves.
(b) The camera is used to photograph a thunderstorm. Thunder and lightning are caused at the same time. The photographer sees the flash of lightning before he hears the thunder. (Sub-topic: P3.1)
(i) Explain why the photographer sees the lightning before he hears the thunder.
▶️Answer/Explanation
Answer: Light travels much faster than sound, so the light from the lightning reaches the photographer before the sound of the thunder.
(ii) Explain why an astronaut orbiting the Earth in a space station sees the lightning but does not hear the thunder.
▶️Answer/Explanation
Answer: The astronaut can see the lightning because light can travel through the vacuum of space. However, sound cannot travel through a vacuum, so the astronaut cannot hear the thunder.
(c) When electronic equipment is recycled, some of the materials can be sorted using magnets. (Sub-topic: P4.1)
(i) In a recycling factory, an electromagnet is used to sort steel from other metals. Explain why an electromagnet is used to sort the steel.
▶️Answer/Explanation
Answer: Steel is magnetic, so it is attracted to the electromagnet. The electromagnet can be turned on and off, allowing the steel to be easily separated from non-magnetic materials.
(ii) Some materials at the recycling factory were tested to see if they conducted electricity. Complete Table 9.1 by placing a tick (✓) in the electrical conductor column or electrical insulator column to correctly describe each material.
Table 9.1
| electrical conductor | electrical insulator | |
|---|---|---|
| aluminium | ||
| cardboard | ||
| copper | ||
| polystyrene | ||
| PVC |
▶️Answer/Explanation
Answer:
| electrical conductor | electrical insulator | |
|---|---|---|
| aluminium | ✓ | |
| cardboard | ✓ | |
| copper | ✓ | |
| polystyrene | ✓ | |
| PVC | ✓ |
Question 10 (Sub-topic: B13.2)
Fig. 10.1 is a drawing of a person doing a parachute jump. Before the jump, the person experiences a large increase in the production of the hormone adrenaline, which targets the liver and the heart.
(a) Describe how adrenaline is transferred to the heart and the liver.
▶️Answer/Explanation
Adrenaline is transferred to the heart and the liver through the bloodstream. It is released into the blood by the adrenal glands and travels to target organs like the heart and liver.
(b) Place ticks (✓) in the boxes to show all the effects of adrenaline on the body in Table 10.1.
| Effect | Tick |
|---|---|
| Decreased pulse rate | |
| Increased breathing rate | |
| Increased transpiration | |
| Mutation of DNA | |
| Widened pupils |
▶️Answer/Explanation
Adrenaline increases breathing rate and widens pupils. It does not decrease pulse rate, increase transpiration, or cause DNA mutation.
(c) One other effect of adrenaline is an increased rate of respiration.
(i) State the word equation for respiration.
▶️Answer/Explanation
Glucose + Oxygen → Carbon Dioxide + Water + Energy
(ii) State why respiration is needed for muscle contraction.
▶️Answer/Explanation
Respiration releases energy, which is needed for muscle contraction.
(d) Respiration is one of the characteristics of living things. State two other characteristics of living things.
▶️Answer/Explanation
1. Movement
2. Growth
Question 11 (Sub-topic: B15.4)
Petroleum and natural gas are extracted from the Earth.
(a) Gasoline is a useful product made from petroleum by fractional distillation.
(i) State a use for gasoline.
▶️Answer/Explanation
Gasoline is used as fuel for cars.
(ii) State one other useful product made from petroleum by fractional distillation.
▶️Answer/Explanation
Diesel oil is another useful product made from petroleum by fractional distillation.
(b) Compound G is the main constituent of natural gas.
(i) State the name of compound G.
▶️Answer/Explanation
Compound G is methane.
(ii) Fig. 11.1 is a diagram of one molecule of compound G.
On Fig. 11.1, complete the key to identify the atoms in the molecule of G.
▶️Answer/Explanation
The key should identify carbon and hydrogen atoms in the molecule of methane (CH4).
(c) Alkanes are saturated compounds.
Alkenes are unsaturated compounds.
(i) Describe a test and its results that shows whether a compound is an alkane or an alkene.
▶️Answer/Explanation
Test: Add bromine water to the compound.
Result with an alkane: The bromine water remains orange/brown.
Result with an alkene: The bromine water turns colorless.
(ii) Describe the difference in the covalent bonding in alkanes and in alkenes.
▶️Answer/Explanation
Alkanes have only single covalent bonds between carbon atoms, while alkenes have at least one double covalent bond between carbon atoms.
(iii) State the name of the chemical reaction that makes alkenes from alkanes.
▶️Answer/Explanation
The chemical reaction is called cracking.
Question 12 (Sub-topic: P4.3.2)
(a) Fig. 12.1 shows a circuit containing a battery of 4 cells.
(i) Name the components P and Q.
▶️Answer/Explanation
Component P: Variable resistor
Component Q: Voltmeter
(ii) The battery is a source of electromotive force (e.m.f.). State the unit of e.m.f.
▶️Answer/Explanation
Unit of e.m.f.: Volt (V)
(iii) The switch is closed and both lamps light up. Readings are recorded on ammeters A₁ and A₂. Describe the difference, if any, in the readings of A₁ and A₂. Explain your answer.
▶️Answer/Explanation
Difference: Ammeter 1 will be lower than ammeter 2
Explanation: Current from the source is larger than the current in each branch. In a parallel circuit, the total current is divided between the branches, so the current in the main circuit (A₁) is the sum of the currents in the branches (A₂).
(b) Fig. 12.2 shows a mains operated d.c. power source.
Identify one electrical hazard on Fig. 12.2.
▶️Answer/Explanation
Electrical hazard: Damaged cable, insulation damaged
(c) Argon gas is used in some types of lamp. An argon atom has the chemical symbol \( \frac{40}{18} \)Ar. State the composition of the nucleus of an atom of Argon.
▶️Answer/Explanation
Composition of the nucleus: 18 protons and 22 neutrons
(d) A sample of radioactive rock was tested to see if it emitted \(\alpha\)-particles.
(i) Describe how a radiation detector could be used to show that \(\alpha\)-particles were being emitted.
▶️Answer/Explanation
Description: Counts are recorded without paper. Put paper in front of the sample to see if counts reduce. If the counts reduce significantly, it indicates that \(\alpha\)-particles are being emitted, as \(\alpha\)-particles are easily blocked by paper.
(ii) When the sample of radioactive rock is removed from the detector, the detector continues to record some radiation. Explain this observation.
▶️Answer/Explanation
Explanation: Background radiation is always present, which is detected by the radiation detector even when the radioactive sample is removed.