Question 1
(a) It is recommended that people eat a balanced diet. (Sub-topic: B7.1)
Place a tick (✓) next to the sentence that best describes a balanced diet.
| A balanced diet contains all the required nutrients in the correct amounts. | |
| A balanced diet contains the correct amounts of carbohydrates. | |
| A balanced diet contains lots of fruit and vegetables. | |
| A balanced diet contains no fats or salt. |
▶️Answer/Explanation
Tick: A balanced diet contains all the required nutrients in the correct amounts.
(b) The boxes on the left show some nutrients. The boxes on the right show why the nutrients are needed by the body.
Draw lines to link each nutrient with why it is needed by the body. (Sub-topic: B7.1)
▶️Answer/Explanation
carbohydrate – main source of energy
fats – insulation
protein – used for growth and repair
vitamin D – for bones and teeth
(c) List the three chemical elements that make up carbohydrates. (Sub-topic: B4.1)
▶️Answer/Explanation
carbon, hydrogen, and oxygen
(d) Benedict’s solution can be used to test for the presence of one type of carbohydrate. Name the carbohydrate that Benedict’s solution is used to test for. (Sub-topic: B4.1)
▶️Answer/Explanation
reducing sugar
(e) Name the component of the diet that prevents constipation. (Sub-topic: B7.1)
▶️Answer/Explanation
fibre
(f) Eating less sugar can help prevent tooth decay. Describe one other way of taking care of teeth. (Sub-topic: B7.1)
▶️Answer/Explanation
Regular brushing of teeth.
(g) Circle the two processes that occur in the mouth. (Sub-topic: B7.2)
ingestion digestion egestion fertilisation photosynthesis pollination transpiration
▶️Answer/Explanation
ingestion and digestion
Question 2 (Sub-topic: C9.4)
(a) Copper and sodium are metals. Copper is a transition element. Sodium is not a transition element. It is found in Group I of the Periodic Table. Some properties of metallic elements are listed.
Properties:
A: act as a catalyst
B: form coloured compounds
C: good conductor of electricity
D: good conductor of thermal energy
E: malleable
F: non-magnetic
State the letters (A to F) of the two properties that describe copper but do not describe sodium.
▶️Answer/Explanation
Answer: A and B
Copper is a transition metal and can act as a catalyst (A) and form coloured compounds (B). Sodium, being an alkali metal, does not exhibit these properties.
(b) Copper(II) oxide is heated with carbon. Copper and carbon dioxide are made.
(i) Construct the word equation for the reaction between copper(II) oxide and carbon.
▶️Answer/Explanation
Copper(II) oxide + carbon → copper + carbon dioxide
(ii) State the chemical test for carbon dioxide gas and the observation for a positive result.
▶️Answer/Explanation
Test: Bubble the gas through limewater.
Observation: The limewater turns cloudy/milky.
(iii) Explain why copper(II) oxide is described as a basic oxide.
▶️Answer/Explanation
Copper(II) oxide is a metal oxide, and metal oxides are generally basic. They react with acids to form salts and water, which is a characteristic of basic oxides.
(c) Metals can be coated with a layer of copper using electroplating. Electroplating uses the process of electrolysis. Use words from the list to complete the sentence to define the term electrolysis.
Each word may be used once or not at all.
covalent electricity gas ionic molten
solid solution time water
Electrolysis always involves the breakdown of …… compounds when …… or in aqueous …… by the passage of …… .
▶️Answer/Explanation
Electrolysis always involves the breakdown of ionic compounds when molten or in aqueous solution by the passage of electricity.
(d) Bronze is a mixture of copper and tin.
(i) State the term used to describe a mixture of metals.
▶️Answer/Explanation
Alloy
(ii) Apart from cost, suggest why bronze is used to make coins but pure copper is not used to make coins.
▶️Answer/Explanation
Bronze is tougher and stronger than pure copper, making it more durable for use in coins.
Question 3 (Sub-topic: P3.3)
(a) X-rays and γ-radiation are both forms of ionising radiation used in hospitals.
(i) State one adverse effect of ionising radiation on the human body.
▶️Answer/Explanation
Ionising radiation can cause mutations in DNA, which may lead to cancer or other genetic disorders.
(ii) State one use of X-rays in a hospital.
▶️Answer/Explanation
X-rays are commonly used in hospitals for imaging internal structures, such as bones, to diagnose fractures or other abnormalities.
(iii) Fig. 3.1 shows an incomplete electromagnetic spectrum. Write γ-radiation and X-rays in their correct positions in Fig. 3.1.
▶️Answer/Explanation
The electromagnetic spectrum is arranged in order of increasing wavelength and decreasing frequency. γ-radiation has the highest frequency and shortest wavelength, followed by X-rays.
(iv) State one property that is the same for all electromagnetic waves.
▶️Answer/Explanation
All electromagnetic waves, regardless of their frequency or wavelength, travel at the speed of light in a vacuum, which is approximately \(3 \times 10^8\) m/s.
(b) A radioactive isotope is used in medical tests as a radioactive tracer. Fig. 3.2 shows the results of an experiment to measure how the radioactivity of the isotope changes with time.
Use Fig. 3.2 to determine the half-life of the isotope in hours. Show your working.
▶️Answer/Explanation
To determine the half-life, observe the time it takes for the radioactivity to decrease by half. From the graph, if the initial activity is 1000 counts and it drops to 500 counts in 6 hours, the half-life is 6 hours.
(c) Ultrasound waves are also used in hospitals. Ultrasound waves are sound waves with a frequency greater than the highest audible frequency of a human.
(i) State the meaning of the term frequency.
▶️Answer/Explanation
Frequency is measured in Hertz (Hz) and represents how many wave cycles occur in one second.
(ii) Suggest a frequency for ultrasound waves. State the unit of your answer.
▶️Answer/Explanation
Ultrasound waves have frequencies higher than the human hearing range, which is typically above 20,000 Hz.
(iii) An ultrasound wave travels 21 cm in 0.00025 s. Calculate the speed of the ultrasound wave in m/s.
▶️Answer/Explanation
First, convert 21 cm to meters (0.21 m). Then, use the formula for speed: \( \text{Speed} = \frac{\text{Distance}}{\text{Time}} \). Substituting the values, \( \text{Speed} = \frac{0.21}{0.00025} = 840 \) m/s.
Speed = Distance / Time = 0.21 m / 0.00025 s = 840 m/s.
Question 4 (Sub-topic: B10.1)
(a) Human immunodeficiency virus (HIV) is a sexually transmitted infection. The number of new HIV infections in one country was monitored.
The results are shown in Fig. 4.1.
The number of new infections has decreased since 2002.
(i) Calculate the difference in number of new HIV infections between 2002 and 2009.
▶️Answer/Explanation
Solution:
From Fig. 4.1, the number of new HIV infections in 2002 is approximately 7000, and in 2009, it is approximately 3100. The difference is calculated as:
7000 – 3100 = 3900
So, the difference in the number of new HIV infections between 2002 and 2009 is 3900.
3900
(ii) Suggest two reasons why the number of new HIV infections has decreased since 2002.
▶️Answer/Explanation
Solution:
Two possible reasons for the decrease in the number of new HIV infections since 2002 could be:
- Increased awareness and education about HIV prevention methods, such as the use of condoms.
- Improved access to antiretroviral therapy (ART) and better healthcare services, which reduce the transmission of the virus.
Any two from: use of condoms / femidoms; screening blood transfusions; education; use of clean needles / needle exchange programmes; regular HIV testing; preventative medication; AVP; e.g. practise of abstinence.
(iii) Place a tick (✓) in the box to show one way HIV can be transmitted.
| Option | Tick |
|---|---|
| holding hands | |
| sharing cooking utensils | |
| through breast milk | |
| genetically inherited |
▶️Answer/Explanation
through breast milk
(b) HIV infects white blood cells. Fig. 4.2 shows a photomicrograph of some blood. A white blood cell can be seen in the centre.
(i) Name the part of the white blood cell labelled X in Fig. 4.2.
▶️Answer/Explanation
Solution:
The part of the white blood cell labelled X is the nucleus.
nucleus
(ii) Name the other type of cells visible in Fig. 4.2.
▶️Answer/Explanation
Solution:
The other type of cells visible in Fig. 4.2 are red blood cells.
red blood cells
(iii) State two functions of white blood cells.
▶️Answer/Explanation
Solution:
Two functions of white blood cells are:
- Phagocytosis: Engulfing and digesting pathogens.
- Antibody production: Producing antibodies to neutralize pathogens.
phagocytosis; antibody production
(iv) Name the part of the blood that transports hormones.
▶️Answer/Explanation
Solution:
The part of the blood that transports hormones is the plasma.
plasma
Question 5
(a) Lithium, sodium and potassium are alkali metal elements in the Periodic Table. Table 5.1 shows the melting points of lithium, sodium and potassium. (Sub-topic: C8.2)
| Metal | Melting Point/°C |
|---|---|
| Lithium | 181 |
| Sodium | 98 |
| Potassium | 64 |
State the trend in the melting points of the elements from lithium to potassium.
▶️Answer/Explanation
The melting points decrease from lithium to potassium. This is because as you go down Group I of the Periodic Table, the atomic size increases, and the metallic bonds become weaker, leading to lower melting points.
(b) An atom of sodium has a nucleon number (mass number) of 23 and a proton number (atomic number) of 11. Fig. 5.1 shows the structure of an atom of sodium. (Sub-topic: C2.2)
(i) On Fig. 5.1, complete the labels for the sodium atom.
▶️Answer/Explanation
The sodium atom should be labeled with:
- 11 protons in the nucleus
- 12 neutrons in the nucleus
- 11 electrons in the electron shells (2 in the first shell, 8 in the second shell, and 1 in the third shell).
(ii) State the electronic structure for this sodium atom.
▶️Answer/Explanation
The electronic structure of the sodium atom is 2.8.1, meaning it has 2 electrons in the first shell, 8 electrons in the second shell, and 1 electron in the third shell.
(c) Sodium and chlorine react to form sodium chloride. Fig. 5.2 shows the electronic structure of a sodium atom and a chlorine atom. (Sub-topic: C2.4)
Draw diagrams to show the electronic structures of a sodium ion and of a chloride ion when sodium reacts with chlorine. Include the charge for each ion.
▶️Answer/Explanation
The sodium ion (Na+) will have the electronic structure 2.8, as it loses one electron from the third shell. The chloride ion (Cl–) will have the electronic structure 2.8.8, as it gains one electron in the third shell.
(d) Sodium and chlorine are elements. Sodium chloride is a compound. Describe the difference between an element and a compound. (Sub-topic: C2.1)
▶️Answer/Explanation
An element is a substance made up of only one type of atom, whereas a compound is a substance made up of two or more different types of atoms chemically bonded together. Sodium is an element, and chlorine is also an element, but sodium chloride is a compound formed by the chemical bonding of sodium and chlorine atoms.
Question 6 (Sub-topic: P4.3.2)
(a) An information booklet about an electric oven states that the weight of the oven is 50 kg. Explain why this statement is incorrect.
▶️Answer/Explanation
The statement is incorrect because weight is a force measured in newtons (N), not in kilograms (kg). The correct unit for weight is newtons, while kilograms are used to measure mass. The weight of the oven can be calculated using the formula \( W = mg \), where \( m \) is the mass and \( g \) is the acceleration due to gravity (approximately 9.8 m/s²). Therefore, the weight of the oven would be \( 50 \, \text{kg} \times 9.8 \, \text{m/s}^2 = 490 \, \text{N} \).
(b) The oven contains two lamps connected in parallel. One lamp has a resistance of 600 Ω and the other lamp has a resistance of 1200 Ω. Circle the correct value for the combined resistance of the two lamps connected in parallel.
400 Ω 600 Ω 900 Ω 1200 Ω 1800 Ω
Explain your answer.
▶️Answer/Explanation
The correct value for the combined resistance of the two lamps connected in parallel is 400 Ω. The formula for calculating the combined resistance \( R \) of two resistors in parallel is: \[ \frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} \] Substituting the given values: \[ \frac{1}{R} = \frac{1}{600} + \frac{1}{1200} = \frac{2}{1200} + \frac{1}{1200} = \frac{3}{1200} = \frac{1}{400} \] Therefore, \( R = 400 \, \Omega \).
(c) The oven contains a fan driven by an electric motor. Fig. 6.1 shows a simple d.c. electric motor.
State two ways of increasing the turning effect on the coil.
▶️Answer/Explanation
Two ways to increase the turning effect on the coil are:
- Increasing the current through the coil.
- Increasing the strength of the magnetic field.
(d) Fig. 6.2 shows a metal saucepan filled with water being heated.
(i) The arrow shows the start of a convection current. Draw more arrows on Fig. 6.2 to show the convection current in water.
▶️Answer/Explanation
The convection current in water can be represented by arrows moving upwards from the heated base of the saucepan and then moving downwards along the sides as the water cools. This creates a circular flow of water.
(ii) When the base of the metal saucepan is heated, the metal expands. State one example where the thermal expansion of a metal is a problem.
▶️Answer/Explanation
One example where the thermal expansion of a metal is a problem is in railway tracks. As the temperature increases, the metal tracks expand, which can cause them to buckle if there is no room for expansion.
(e)(i) When the water is heated in the saucepan, some of the water evaporates. Eventually the temperature of the water reaches boiling point. State the boiling point of water.
▶️Answer/Explanation
The boiling point of water is 100 °C at standard atmospheric pressure.
(ii) State the meaning of the term boiling point.
▶️Answer/Explanation
The boiling point is the temperature at which a liquid changes into a gas at a given pressure. For water, this occurs at 100 °C at standard atmospheric pressure.
Question 7
Fig. 7.1 is a photomicrograph of a cross-section of a root.
(a) Identify the parts of the root labelled A and B in Fig. 7.1. (Sub-topic: B8.1)
▶️Answer/Explanation
A: xylem
B: phloem
Explanation: The xylem and phloem are the two main types of vascular tissue in plants. The xylem is responsible for transporting water and mineral ions from the roots to the rest of the plant, while the phloem transports sucrose and amino acids from the leaves to other parts of the plant.
(b) The cell labelled C absorbs mineral ions from the soil. (Sub-topic: B8.2)
(i) Name this cell.
▶️Answer/Explanation
root hair cell
Explanation: Root hair cells are specialized cells in the roots of plants that increase the surface area for absorption of water and mineral ions from the soil.
(ii) Name one other substance absorbed by the cell labelled C in Fig. 7.1.
▶️Answer/Explanation
water
Explanation: In addition to mineral ions, root hair cells also absorb water from the soil, which is essential for the plant’s survival and growth.
(c) Chlorophyll is needed for photosynthesis. (Sub-topic: B6.1)
(i) Name the mineral ion needed to make chlorophyll.
▶️Answer/Explanation
magnesium
Explanation: Magnesium is a key component of chlorophyll, the green pigment in plants that is essential for photosynthesis.
(ii) State the word equation for photosynthesis.
▶️Answer/Explanation
carbon dioxide + water → glucose + oxygen
Explanation: Photosynthesis is the process by which plants convert carbon dioxide and water into glucose and oxygen using sunlight as energy.
(d) Fig. 7.2 is a diagram of a seed germinating underground. (Sub-topic: B15.3)
(i) Draw two arrows on Fig. 7.2 to show the direction the root and shoot will grow.
▶️Answer/Explanation
shoot arrow pointing upwards and root arrow pointing downwards
Explanation: During germination, the shoot grows upwards towards the light, while the root grows downwards into the soil in response to gravity.
(ii) There is no light reaching the seed underground. Name the stimulus the root would be responding to in Fig. 7.2.
▶️Answer/Explanation
gravity
Explanation: The root responds to gravity, a phenomenon known as gravitropism, which causes it to grow downwards into the soil.
(iii) State two environmental conditions seeds need to germinate.
▶️Answer/Explanation
1: warm / suitable temperature
2: oxygen
Explanation: Seeds require specific environmental conditions to germinate, including a suitable temperature and the presence of oxygen for respiration.
Question 8 (Sub-topic: C11.5)
(a) Fig. 8.1 shows three hydrocarbon molecules X, Y and Z.
Hydrocarbon molecule X is unsaturated.
(i) Explain why molecule X is unsaturated.
▶️Answer/Explanation
Molecule X is unsaturated because it contains a carbon-carbon double bond (C=C). Unsaturated hydrocarbons have at least one double or triple bond between carbon atoms, which allows them to undergo addition reactions.
(ii) State the name of molecule X.
▶️Answer/Explanation
The name of molecule X is ethene.
(iii) An aqueous solution of element P is used to test if hydrocarbons X and Y are saturated or unsaturated. State the name of element P.
▶️Answer/Explanation
The name of element P is bromine.
(iv) Describe what, if anything, is observed when an aqueous solution of element P is mixed with hydrocarbon molecule X and with hydrocarbon molecule Y.
▶️Answer/Explanation
When an aqueous solution of bromine is mixed with hydrocarbon molecule X (ethene), the bromine solution will decolorize or become colorless, indicating that an addition reaction has occurred. When mixed with hydrocarbon molecule Y (a saturated hydrocarbon), the bromine solution will remain orange as no reaction occurs.
(b)(i) When hydrocarbon molecule Y is completely combusted in oxygen, carbon dioxide and water are made. Balance the symbol equation for this reaction.
\[ \text{CH}_4 + \ldots \text{O}_2 \longrightarrow \text{CO}_2 + \ldots \text{H}_2\text{O} \]
▶️Answer/Explanation
The balanced equation is:
\[ \text{CH}_4 + 2\text{O}_2 \longrightarrow \text{CO}_2 + 2\text{H}_2\text{O} \]
(ii) This reaction is an exothermic reaction. State what is meant by an exothermic reaction.
▶️Answer/Explanation
An exothermic reaction is a chemical reaction that releases energy in the form of heat to the surroundings.
(c) Ethanol has the formula \( \text{C}_2\text{H}_5\text{OH} \).
(i) Explain why ethanol is not a hydrocarbon.
▶️Answer/Explanation
Ethanol is not a hydrocarbon because it contains an oxygen atom in its structure (C2H5OH). Hydrocarbons consist only of hydrogen and carbon atoms.
(ii) State two methods of producing ethanol.
▶️Answer/Explanation
Two methods of producing ethanol are:
- Fermentation of sugars by yeast.
- Reaction of ethene with steam in the presence of a catalyst.
Question 9 (Sub-topic: P1.2)
(a) Fig. 9.1 shows an aircraft on a runway.
Use the letters A, B, C or D to complete the sentences. Each letter may be used once, more than once or not at all.
When the aircraft is at rest on the runway, force A is equal to force ………….. and also force B is equal to force ………….. .
When the aircraft starts to accelerate along the runway, forces ………….. and ………….. are unbalanced.
▶️Answer/Explanation
When the aircraft is at rest on the runway, force A is equal to force C and also force B is equal to force D.
When the aircraft starts to accelerate along the runway, forces B and D are unbalanced.
(b) Fig. 9.2 shows the speed-time graph for the aircraft during part of its flight when it is travelling at constant height.
(i) Label with a cross (X) a part of the flight when the aircraft is accelerating.
(ii) State which section of the graph shows the aircraft travelling with no acceleration. Explain your answer.
▶️Answer/Explanation
(i) The part of the graph where the speed is increasing (e.g., the initial upward slope) should be labeled with a cross (X).
(ii) The section of the graph where the speed is constant (e.g., the horizontal line) shows the aircraft travelling with no acceleration. This is because the speed is not changing, indicating that the forces are balanced and there is no acceleration.
(c) The aircraft fuel is a non-renewable energy source obtained from petroleum.
(i) Identify the form of energy stored in aircraft fuel.
(ii) Name two renewable energy sources.
▶️Answer/Explanation
(i) The form of energy stored in aircraft fuel is chemical energy.
(ii) Two renewable energy sources are solar energy and wind energy.
Question 10 (Sub-topic: B16.1)
(a) A farmer keeps ponies. The ponies show variation in height. The farmer sells the smaller ponies for more money than the larger ponies.
(i) Name the type of variation shown by differences in height of the ponies.
▶️Answer/Explanation
Answer: Continuous variation.
Explanation: Continuous variation refers to differences in characteristics that can take any value within a range, such as height, weight, or skin color. In this case, the height of the ponies can vary across a spectrum, making it an example of continuous variation.
(ii) Complete the sentences to describe the method the farmer uses to increase the number of smaller ponies on the farm.
The farmer selects the ponies with the desirable feature.
These ponies are then ………….. .
The ………….. offspring are then selected and used for ………….. .
This process is then ………….. over many generations.
▶️Answer/Explanation
Answer:
These ponies are then bred.
The smallest offspring are then selected and used for breeding.
This process is then repeated over many generations.
Explanation: The farmer is using selective breeding to increase the number of smaller ponies. By selecting the smallest ponies and breeding them, the farmer ensures that the desirable trait (smaller size) is passed on to future generations. This process is repeated over many generations to achieve the desired outcome.
(iii) State the name of the process the farmer uses.
▶️Answer/Explanation
Answer: Selective breeding.
Explanation: Selective breeding is the process of choosing specific animals or plants with desirable traits to breed together, with the aim of producing offspring with those traits. In this case, the farmer is selectively breeding ponies to produce smaller offspring.
(b) The inheritance of sex in ponies is the same as in humans.
(i) Complete Table 10.1 to show the inheritance of sex.
▶️Answer/Explanation
Answer:
Explanation: In most mammals, including ponies and humans, males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). This determines the sex of the offspring.
(ii) State the ratio of male to female offspring shown in Table 10.1.
▶️Answer/Explanation
Answer: 1:1
Explanation: The ratio of male to female offspring is 1:1 because there is an equal chance of inheriting either an X or a Y chromosome from the father, resulting in an equal number of males (XY) and females (XX).
(c) Chromosomes contain genes.
Define the term gene.
▶️Answer/Explanation
Answer: A gene is a length of DNA that codes for a protein.
Explanation: Genes are segments of DNA located on chromosomes that contain the instructions for the synthesis of proteins. These proteins are responsible for various traits and functions in an organism.
Question 11
(a)(i) Table 11.1 shows information about three colourless liquids J, K and L. (Sub-topic: C7.1)
Complete Table 11.1 by inserting the pH for pure water.
| Liquid | Description | pH |
|---|---|---|
| J | Acid rain | 4 |
| K | Dilute sulfuric acid | 2 |
| L | Pure water | …… |
▶️Answer/Explanation
The pH of pure water is 7, as it is neutral.
(ii) Name one gas that causes acid rain. (Sub-topic: C10.2)
▶️Answer/Explanation
Sulfur dioxide (SO2) is one of the gases that cause acid rain.
(iii) Name the indicator used to find the pH of a liquid. (Sub-topic: C7.1)
▶️Answer/Explanation
Universal indicator is used to find the pH of a liquid.
(b) A student reacts dilute sulfuric acid with four metals. The student’s observations are shown in Table 11.2. (Sub-topic: C9.4)
| Metal | Observation |
|---|---|
| Copper | Does not react |
| Iron | Reacts slowly |
| Lithium | Reacts explosively |
| Magnesium | Reacts rapidly |
Place the four metals in order of their reactivity from the most reactive to the least reactive.
▶️Answer/Explanation
The order of reactivity from most reactive to least reactive is: Lithium > Magnesium > Iron > Copper.
(c)(i) Table 11.2 shows that magnesium reacts rapidly with sulfuric acid. State the name of one of the products of this reaction. (Sub-topic: C6.2)
▶️Answer/Explanation
One of the products of the reaction between magnesium and sulfuric acid is hydrogen gas (H2).
(ii) Suggest two ways of increasing the rate of reaction between magnesium and dilute sulfuric acid. (Sub-topic: C6.2)
▶️Answer/Explanation
Two ways to increase the rate of reaction are:
- Increase the temperature of the sulfuric acid.
- Increase the concentration of the sulfuric acid.
(iii) The gas formed in this reaction is not a greenhouse gas. State the names of two greenhouse gases. (Sub-topic: C10.2)
▶️Answer/Explanation
Two greenhouse gases are carbon dioxide (CO2) and methane (CH4).
Question 12
(a) A bicycle has a front lamp, X, and a rear lamp, Y, connected in parallel across a battery. Both lamps are controlled by a single switch. (Sub-topic: P4.3.2)
(i) Draw a circuit diagram using standard electrical symbols showing two lamps connected in parallel across a battery. Include the switch in the diagram.
(ii) When the switch is closed, lamp X has a resistance of 6.0 Ω. The potential difference across the lamp is 3.0 V. Calculate the current in lamp X.
▶️Answer/Explanation
12(a)(i) The circuit diagram should show:
- A battery symbol with positive and negative terminals.
- Two lamps (X and Y) connected in parallel.
- A single switch connected in series with the battery to control both lamps.
- Wires connecting the components to form a complete circuit.
12(a)(ii) To calculate the current in lamp X, use Ohm’s Law: \[ I = \frac{V}{R} \] Where:
- \( V = 3.0 \, \text{V} \) (potential difference across the lamp)
- \( R = 6.0 \, \Omega \) (resistance of the lamp)
\[ I = \frac{3.0}{6.0} = 0.5 \, \text{A} \] So, the current in lamp X is 0.5 A.
(b) Bicycle frames can be made from either steel or aluminium. (Sub-topic: P1.4)
(i) Suggest and explain a simple way of deciding whether the frame of the bicycle is made from steel or aluminium.
(ii) A bicycle frame is made from aluminium. A block of aluminium has a mass of 8100 g and a volume of 3000 cm³. Calculate the density of aluminium.
▶️Answer/Explanation
12(b)(i) A simple way to determine whether the frame is made from steel or aluminium is to use a magnet. Steel is magnetic, so if the magnet sticks to the frame, it is made of steel. Aluminium is non-magnetic, so if the magnet does not stick, the frame is likely made of aluminium.
12(b)(ii) To calculate the density of aluminium, use the formula: \[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \] Where:
- Mass = 8100 g
- Volume = 3000 cm³
\[ \text{Density} = \frac{8100}{3000} = 2.7 \, \text{g/cm}^3 \] So, the density of aluminium is 2.7 g/cm³.
(c) The bicycle has a mirror to help the cyclist see behind him. The cyclist sees a police car in his mirror. This is shown in Fig. 12.1. (Sub-topic: P3.2.1)
(i) Use Fig. 12.1 to describe two characteristics of an image seen in a plane mirror apart from size.
▶️Answer/Explanation
12(c)(i) Two characteristics of an image seen in a plane mirror are:
- Upright: The image is not inverted; it appears the same way up as the object.
- Laterally inverted: The image is flipped horizontally, meaning the left side of the object appears on the right side of the image and vice versa.