Question 1 (Sub-topic – B12.1)
(a) Table 1.1 shows some features of aerobic and anaerobic respiration.
Place ticks (✓) in the boxes to show all the correct features for each type of respiration.
| Type of Respiration | Oxygen is a Reactant | Glucose is a Reactant | Lactic Acid is a Product | Carbon Dioxide is a Product |
|---|---|---|---|---|
| Aerobic | ||||
| Anaerobic Respiration in Muscles | ||||
| Anaerobic Respiration in Yeast |
▶️Answer/Explanation
| Type of Respiration | Oxygen is a Reactant | Glucose is a Reactant | Lactic Acid is a Product | Carbon Dioxide is a Product |
|---|---|---|---|---|
| Aerobic | ✓ | ✓ | ✓ | |
| Anaerobic Respiration in Muscles | ✓ | ✓ | ||
| Anaerobic Respiration in Yeast | ✓ | ✓ |
Explanation:
- Aerobic Respiration: Oxygen is required as a reactant, glucose is broken down, and carbon dioxide is produced as a byproduct. Lactic acid is not produced in aerobic respiration.
- Anaerobic Respiration in Muscles: Oxygen is not required, glucose is broken down, and lactic acid is produced as a byproduct. Carbon dioxide is not produced in this process.
- Anaerobic Respiration in Yeast: Oxygen is not required, glucose is broken down, and carbon dioxide is produced as a byproduct. Lactic acid is not produced in this process.
(b) State one industrial use of anaerobic respiration in yeast.
▶️Answer/Explanation
Answer: Bread making / Brewing (alcohol production).
Explanation: Anaerobic respiration in yeast is used in the fermentation process, which is essential in baking bread and producing alcoholic beverages like beer and wine. During fermentation, yeast converts sugars into carbon dioxide and ethanol, which helps in leavening bread and producing alcohol.
(c) Describe one disadvantage of anaerobic respiration in terms of energy release.
▶️Answer/Explanation
Answer: Less energy is released per glucose molecule compared to aerobic respiration.
Explanation: Anaerobic respiration releases only a small amount of energy (2 ATP molecules per glucose molecule) compared to aerobic respiration, which releases a much larger amount of energy (up to 38 ATP molecules per glucose molecule). This makes anaerobic respiration less efficient in terms of energy production.
Question 2 (Sub-topic – C12.3)
(a) Fig. 2.1 shows how paper chromatography is used to separate a mixture of red and blue inks.
(i) Explain why the start line is drawn in pencil rather than in ink.
▶️Answer/Explanation
Pencil does not dissolve in the solvent, whereas ink would dissolve and interfere with the separation process.
(ii) The result of the chromatography experiment is shown in Fig. 2.2.
The blue spot moves 14.2 cm and the solvent front moves 15.3 cm. Calculate the \( R_f \) value of the substance in the blue spot.
Show your working.
▶️Answer/Explanation
\( R_f = \frac{\text{distance travelled by substance}}{\text{distance travelled by solvent}} = \frac{14.2}{15.3} = 0.928 \).
(b) W, X, Y and Z are mixtures of food colourings. These mixtures of food colourings are investigated using paper chromatography. The result of the chromatography experiment is shown in Fig. 2.3.
(i) State which mixture contains an insoluble food colouring.
▶️Answer/Explanation
Mixture X contains an insoluble food colouring.
(ii) Explain which mixture is separated into the greatest number of soluble food colourings. Refer to Fig. 2.3 in your answer.
▶️Answer/Explanation
Mixture Z is separated into the greatest number of soluble food colourings because it has the most spots above the line, indicating the presence of multiple soluble components.
(c) A scientist tests the melting point of a sample of a substance. The substance starts melting at 96 °C but does not melt completely until the temperature is 113 °C. According to a data book, the melting point of the substance is 116 °C.
Explain, using the information given, if this sample of the substance is pure or impure.
▶️Answer/Explanation
The sample is impure because it melts over a range of temperatures (96 °C to 113 °C) rather than at a single sharp melting point. Additionally, the melting range is lower than the reference melting point of 116 °C, which is another indication of impurity.
Question 3 (Sub-topics – P4.2.4, P4.5.4)
Fig. 3.1 shows a circuit used by a student to investigate the resistance of a metal wire.
(a) Suggest why a fixed resistor has been included in the circuit.
▶️Answer/Explanation
The fixed resistor is included in the circuit to reduce the potential difference across the wire or to limit the current through the wire, preventing it from overheating or melting.
(b) When the switch is closed, the voltmeter reads 1.2 V and the ammeter reads 0.40 A.
(i) Calculate the resistance of the wire.
▶️Answer/Explanation
Using Ohm’s Law, \( R = \frac{V}{I} \), where \( V = 1.2 \, \text{V} \) and \( I = 0.40 \, \text{A} \): \[ R = \frac{1.2}{0.40} = 3.0 \, \Omega \] The resistance of the wire is 3.0 Ω.
(ii) Calculate the amount of energy dissipated by the wire in 15 seconds. State the unit of your answer.
▶️Answer/Explanation
The energy dissipated can be calculated using the formula \( E = VIt \), where \( V = 1.2 \, \text{V} \), \( I = 0.40 \, \text{A} \), and \( t = 15 \, \text{s} \): \[ E = 1.2 \times 0.40 \times 15 = 7.2 \, \text{J} \] The energy dissipated is 7.2 joules (J).
(iii) State the energy transfer happening in the wire as current passes through it.
▶️Answer/Explanation
The energy transfer in the wire is from electrical energy to thermal energy (heat) due to the resistance of the wire.
(c) The wire is replaced with a second wire made of the same metal and of the same length but with twice the cross-sectional area. Determine the resistance of the second wire.
▶️Answer/Explanation
The resistance \( R \) of a wire is inversely proportional to its cross-sectional area \( A \). If the cross-sectional area is doubled, the resistance is halved: \[ R_{\text{new}} = \frac{R_{\text{original}}}{2} = \frac{3.0}{2} = 1.5 \, \Omega \] The resistance of the second wire is 1.5 Ω.
(d) The student wants to calculate the cross-sectional area of the wire. State the quantity the student needs to measure and suggest a suitable measuring instrument to use.
▶️Answer/Explanation
The student needs to measure the diameter of the wire. A suitable measuring instrument is a micrometer screw gauge, which can measure small diameters with high precision.
(e) Fig. 3.2 shows the wire being placed in between the poles of a permanent magnet.
This causes a force to act on the wire.
(i) Draw an arrow on Fig. 3.2 to show the direction of the force acting on the wire.
▶️Answer/Explanation
The force acting on the wire is directed downwards (use Fleming’s Left-Hand Rule).
(ii) State two ways to increase the size of the force acting on the wire.
▶️Answer/Explanation
Two ways to increase the force are:
- Increase the current flowing through the wire.
- Increase the strength of the magnetic field.
Question 4 (Sub-topics – B7.1, B7.2, B7.3)
(a) Table 4.1 shows the vitamin D content in 100 g of different foods.
| Type of food | Vitamin D content in 100 g of food / μg |
|---|---|
| soya milk | 1.3 |
| cow milk | 2.8 |
| salmon | 15.8 |
| swordfish | 19.8 |
| tofu | 4.0 |
| mushroom | 11.2 |
The recommended dietary allowance (RDA) of vitamin D is 15.0 μg.
Vegans do not eat any animal products and consume plant-based products such as tofu and soya milk.
(i) Calculate the mass of tofu you would need to eat to get your RDA of vitamin D.
▶️Answer/Explanation
375 g
Solution:
To calculate the mass of tofu needed to meet the RDA of vitamin D, we use the formula:
\[ \text{Mass of tofu} = \left( \frac{\text{RDA of vitamin D}}{\text{Vitamin D content per 100 g of tofu}} \right) \times 100 \]
Substituting the given values:
\[ \text{Mass of tofu} = \left( \frac{15.0 \, \mu g}{4.0 \, \mu g} \right) \times 100 = 375 \, g \]
Therefore, you would need to eat 375 g of tofu to meet your RDA of vitamin D.
(ii) Explain why vegans may be more at risk of vitamin D deficiency than people who eat animal products.
▶️Answer/Explanation
Plant-based foods contain less vitamin D than animal products, so vegans need to eat larger amounts to meet their RDA.
Solution:
Vegans may be at a higher risk of vitamin D deficiency because plant-based foods generally contain lower amounts of vitamin D compared to animal products. For example, tofu contains only 4.0 μg of vitamin D per 100 g, while salmon contains 15.8 μg per 100 g. This means that vegans would need to consume larger quantities of plant-based foods to meet their RDA of vitamin D, which may not always be practical or achievable.
(b) Explain why pregnant women are recommended to increase their vitamin D intake.
▶️Answer/Explanation
Vitamin D is needed for the formation of the baby’s bones.
Solution:
Pregnant women are recommended to increase their vitamin D intake because vitamin D is essential for the development of the baby’s bones. Adequate vitamin D levels help in the absorption of calcium, which is crucial for the formation of strong bones and teeth in the developing fetus. Insufficient vitamin D during pregnancy can lead to complications such as rickets in the baby or osteomalacia in the mother.
(c) Name one disease caused by protein deficiency in the diet.
▶️Answer/Explanation
kwashiorkor
Solution:
One disease caused by protein deficiency in the diet is kwashiorkor. This condition is characterized by swelling, particularly in the abdomen, and is common in children who do not consume enough protein.
(d) Describe the chemical digestion of protein in the stomach.
▶️Answer/Explanation
Proteins are broken down into smaller polypeptides by the enzyme pepsin in the stomach.
Solution:
In the stomach, proteins are chemically digested by the action of the enzyme pepsin. Pepsin is secreted in its inactive form, pepsinogen, by the gastric glands. When pepsinogen comes into contact with hydrochloric acid (HCl) in the stomach, it is converted into active pepsin. Pepsin then breaks down proteins into smaller polypeptides by hydrolyzing peptide bonds.
(e) Describe how chemical digestion differs from mechanical digestion.
▶️Answer/Explanation
Chemical digestion breaks down food molecules using enzymes, while mechanical digestion physically breaks food into smaller pieces.
Solution:
Chemical digestion involves the breakdown of food molecules into smaller, absorbable molecules through the action of enzymes and other chemicals. For example, proteins are broken down into amino acids by enzymes like pepsin and trypsin. In contrast, mechanical digestion involves the physical breakdown of food into smaller pieces without changing its chemical composition. This is achieved through processes like chewing in the mouth and churning in the stomach.
Question 5
An atom of chlorine has a proton number (atomic number) of 17 and a nucleon number (mass number) of 37.
(a) (i) Complete Table 5.1 to show the numbers of protons, neutrons, and electrons in this atom of chlorine. (Sub-topic – C2.2)
| Particle | Number |
|---|---|
| Proton | |
| Neutron | |
| Electron |
▶️Answer/Explanation
| Particle | Number |
|---|---|
| Proton | 17 |
| Neutron | 20 |
| Electron | 17 |
The number of protons in an atom is equal to its atomic number, which is 17 for chlorine. The number of neutrons is calculated by subtracting the atomic number from the mass number: 37 – 17 = 20. The number of electrons in a neutral atom is equal to the number of protons, which is also 17.
(ii) Chlorine is in Group VII of the Periodic Table. State what information this gives about the number of electrons in the outer shell of a chlorine atom. (Sub-topic – C2.2)
▶️Answer/Explanation
Chlorine is in Group VII, which means it has 7 electrons in its outer shell.
(iii) Chlorine exists as isotopes. Explain what is meant by the term isotopes. (Sub-topic – C2.3)
▶️Answer/Explanation
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers.
(b) Chlorine atoms bond together to form the covalent molecule, \( \text{Cl}_2 \). Chlorine, \( \text{Cl}_2 \), is a gas at room temperature. Chlorine atoms bond with sodium atoms to form the ionic compound sodium chloride, NaCl. Sodium chloride, NaCl, is a solid at room temperature. Explain why chlorine is a gas but sodium chloride is a solid at room temperature in terms of attractive forces. (Sub-topic – C2.4)
▶️Answer/Explanation
Chlorine (\( \text{Cl}_2 \)) is a gas at room temperature because it consists of covalent molecules with weak intermolecular forces (van der Waals forces) between them. These forces are easily overcome at room temperature, allowing the molecules to move freely. Sodium chloride (NaCl) is a solid at room temperature because it is an ionic compound with strong electrostatic forces of attraction between the positively charged sodium ions (\( \text{Na}^+ \)) and the negatively charged chloride ions (\( \text{Cl}^- \)). These strong forces require a lot of energy to break, which is why NaCl remains solid at room temperature.
(c) Chlorine reacts with sodium bromide, NaBr. Write the balanced symbol equation for this reaction. (Sub-topic – C6.3)
▶️Answer/Explanation
The balanced symbol equation for the reaction between chlorine and sodium bromide is: \[ \text{Cl}_2 + 2\text{NaBr} \rightarrow \text{Br}_2 + 2\text{NaCl} \] In this reaction, chlorine displaces bromine from sodium bromide, forming bromine gas and sodium chloride.
Question 6
Strontium-90 (90Sr) is a radioactive isotope. (Sub-topic – P5.2.1)
(a) Strontium‑90 decays by beta emission to form an isotope of yttrium and a β‑particle.
(i) State the nature of a β-particle.
▶️Answer/Explanation
A β-particle is an electron emitted from the nucleus during radioactive decay.
(ii) Use the correct nuclide notation to complete the symbol equation for this decay process.
\[ \begin{array}{cccc} \text{90} & \text{38} & \rightarrow & \text{……Y} & + & 0 \\ & & & \rightarrow & \text{……} & -1 \\ \end{array} \]
▶️Answer/Explanation
\[ \begin{array}{cccc} \text{90} & \text{38} & \rightarrow & \text{90} & \text{39} & \text{Y} & + & 0 \\ & & & \rightarrow & \text{……} & -1 \\ \end{array} \]
(b) Fig. 6.1 shows how this isotope of strontium can be used in a paper mill to determine the thickness of paper passing through a set of rollers. (Sub-topic – P5.2.2)
Describe and explain what happens to the reading on the automatic counter if the paper becomes thicker.
▶️Answer/Explanation
The reading on the automatic counter would decrease because fewer β-particles would penetrate the thicker paper, resulting in fewer counts being registered.
(c) Table 6.1 shows how the activity of a strontium source varies over a 60-year period. (Sub-topic – P5.2.4)
(i) Use Table 6.1 to determine the half-life of strontium-90.
▶️Answer/Explanation
The half-life of strontium-90 is 30 years. This is determined by observing the time it takes for the activity to decrease from 2000 counts per minute to 1000 counts per minute.
(ii) Suggest why this half-life makes it suitable for use in a paper mill.
▶️Answer/Explanation
The half-life of 30 years makes strontium-90 suitable for use in a paper mill because it does not need to be replaced frequently, and its activity remains relatively stable over a long period, ensuring consistent measurements.
Question 7
(a) Fig. 7.1 is a diagram of the human eye. (Sub-topic – B13.1)
(i) Identify the letter on Fig. 7.1 that represents the part of the eye which:
- carries impulses to the brain
- refracts light as it enters the eye
- controls how much light enters the eye.
(ii) Describe what happens to parts A, E and F when someone changes from focusing on a distant object to focusing on a near object.
▶️Answer/Explanation
(i)
Carries impulses to the brain: H
Refracts light as it enters the eye: C
Controls how much light enters the eye: B
(ii)
A thickens / gets wider / AW;
E slackens / loosens / AW;
F contracts;
(b) The pupil reflex is a response to changes in light intensity. (Sub-topic – B13.1)
(i) Name the part of the eye that is the receptor in a pupil reflex.
(ii) Name the part of the eye that is the effector in a pupil reflex.
▶️Answer/Explanation
(i) retina;
(ii) circular / radial, muscles;
(c) The pupil reflex is an involuntary action. (Sub-topic – B13.1)
Place ticks (✓) next to all the examples of involuntary actions.
| Actions | Tick |
|---|---|
| eating | |
| running | |
| sneezing | |
| sweating | |
| talking |
▶️Answer/Explanation
– sneezing ticked;
– sweating ticked;
(d) Involuntary actions are controlled by the central nervous system. (Sub-topic – B13.1)
Name both parts of the central nervous system.
▶️Answer/Explanation
brain and spinal cord;
Question 8 (Sub-topic – C4.1)
Electrolysis is used to break down ionic compounds using electricity.
(a) Fig. 8.1 shows an electrolysis experiment. Complete the labels on Fig. 8.1.
Choose your answers from the list:
- anion
- anode
- cation
- cathode
- electrolyte
▶️Answer/Explanation
The labels for Fig. 8.1 are as follows:
(b) A student investigates the electrolysis of aqueous copper(II) sulfate using carbon electrodes.
Fig. 8.2 shows her experiment.
(i) A gas is made at the positive electrode. State the name of this gas.
▶️Answer/Explanation
The gas produced at the positive electrode (anode) is oxygen.
(ii) At the negative electrode, copper ions, Cu2+, gain electrons to form copper metal, Cu. Construct the ionic half-equation for the formation of copper at the negative electrode.
▶️Answer/Explanation
The ionic half-equation for the formation of copper at the cathode is: \[ \text{Cu}^{2+} + 2e^- \rightarrow \text{Cu} \]
(c) In the electrolysis of molten lead(II) bromide, bromine is formed at the positive electrode. The ionic half-equation is shown.
\[ 2\text{Br}^- \rightarrow \text{Br}_2 + 2e^- \]
(i) State, in terms of electrons, if this reaction is oxidation or reduction. Explain your answer.
▶️Answer/Explanation
This reaction is oxidation because electrons are lost from the bromide ions (\(\text{Br}^-\)) to form bromine gas (\(\text{Br}_2\)).
(ii) The total mass of bromine gas made in an electrolysis experiment is 20 g. Calculate the volume of bromine gas made. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).
▶️Answer/Explanation
To calculate the volume of bromine gas:
- Calculate the number of moles of bromine gas: \[ \text{Moles of Br}_2 = \frac{\text{Mass}}{\text{Molar mass}} = \frac{20 \, \text{g}}{160 \, \text{g/mol}} = 0.125 \, \text{mol} \]
- Calculate the volume of bromine gas: \[ \text{Volume} = \text{Moles} \times \text{Molar volume} = 0.125 \, \text{mol} \times 24 \, \text{dm}^3/\text{mol} = 3 \, \text{dm}^3 \]
Therefore, the volume of bromine gas produced is 3 dm3.
Question 9 (Sub-topic – P1.2)
Fig. 9.1 shows the motion of a sprinter running a race.
(a) Describe the motion of the sprinter during the first 0.5 seconds of the race.
▶️Answer/Explanation
The sprinter is stationary during the first 0.5 seconds of the race.
(b) Show that the maximum acceleration of the sprinter is \(2.0 \, \text{m/s}^2\).
▶️Answer/Explanation
The maximum acceleration can be calculated using the formula \(a = \frac{\Delta v}{\Delta t}\). From the graph, the change in velocity (\(\Delta v\)) is \(8.0 \, \text{m/s}\) and the time (\(\Delta t\)) is \(4.0 \, \text{s}\). Therefore, \(a = \frac{8.0}{4.0} = 2.0 \, \text{m/s}^2\).
(c) This acceleration is caused by a resultant force of \(160 \, \text{N}\). Calculate the mass of the sprinter.
▶️Answer/Explanation
Using Newton’s second law, \(F = ma\), we can rearrange to find mass: \(m = \frac{F}{a}\). Given \(F = 160 \, \text{N}\) and \(a = 2.0 \, \text{m/s}^2\), the mass \(m = \frac{160}{2.0} = 80 \, \text{kg}\).
(d) Fig. 9.2 shows the forces acting on the sprinter at various points during the race.
The lengths of the arrows represent the magnitude of the forces.
(i) Put a tick \((\sqrt{\cdot})\) in the box which shows the horizontal forces acting on the sprinter 5.0s after the race started.
▶️Answer/Explanation
The first diagram should be ticked, as it shows balanced horizontal forces, indicating constant velocity.
(ii) Use the motion of the sprinter in Fig. 9.1 to explain your answer to (d)(i).
▶️Answer/Explanation
At 5.0 seconds, the sprinter is moving at a constant velocity, which means the forces acting on the sprinter are balanced, resulting in no acceleration.
(e)(i) Describe, in terms of particles and their energies, how the sweat cools the skin.
▶️Answer/Explanation
Sweat evaporates from the skin, and the most energetic particles escape from the liquid surface. This reduces the average kinetic energy of the remaining particles, leading to a cooling effect on the skin.
(ii) Describe two differences between evaporation and boiling.
▶️Answer/Explanation
1. Evaporation can occur at any temperature, while boiling only happens at the boiling point.
2. Evaporation happens only at the surface of the liquid, while boiling occurs throughout the liquid.
Question 10 (Sub-topic – B19.1)
(a)Fig. 10.1 is a flowchart showing the process of eutrophication. Complete the flowchart in Fig. 10.1.
▶️Answer/Explanation
increase of nitrate ions in the water
plants can no longer photosynthesise so they die
dead plants are decomposed by bacteria
dissolved oxygen concentration of the water decreases
(b) Deforestation can result in increased eutrophication, especially when it rains. Suggest why deforestation causes an increase in eutrophication.
▶️Answer/Explanation
Deforestation increases soil erosion, which leads to more nitrate ions being washed into water bodies. These nitrates act as nutrients for algae and other surface plants, leading to eutrophication.
(c) List two undesirable effects of deforestation on animals living in the forest.
▶️Answer/Explanation
1. Loss of habitat for animals.
2. Disruption of the food chain, leading to a decrease in biodiversity.
(d) Trees make their own organic nutrients through photosynthesis. State the term used to describe organisms that make their own nutrients.
▶️Answer/Explanation
Producers
(e) List three substances plants need to make their own organic nutrients.
▶️Answer/Explanation
1. Carbon dioxide
2. Water
3. Chlorophyll
Question 11 (Sub-topic – C11.5)
Ethene and propene are both members of the homologous series called the alkenes.
Fig. 11.1 shows the structures of ethene and propene.
(a) State two reasons why ethene and propene are members of the same homologous series.
▶️Answer/Explanation
Reason 1: Both ethene and propene have the same functional group, which is the carbon-carbon double bond (C=C).
Reason 2: They follow the same general formula for alkenes, which is \( C_nH_{2n} \).
(b) Ethene can be made by the cracking of large alkane molecules.
(i) State the conditions needed for cracking.
▶️Answer/Explanation
Condition 1: High temperature (typically around 600-700°C).
Condition 2: Presence of a catalyst (usually a zeolite catalyst).
(ii) Ethene, \( C_2H_4 \), can be made by the cracking of octane, \( C_8H_{18} \). The balanced symbol equation for the reaction is shown.
\( C_8H_{18} \rightarrow C_4H_{10} + 2C_2H_4 \)
State the name of the other product made and complete Fig. 11.2 to show its structure. Show all the covalent bonds.
▶️Answer/Explanation
Name of the other product: Butane.
Structure of butane:
(c) Ethene reacts with bromine, \( Br_2 \), in an addition reaction. Write the balanced symbol equation for this reaction.
▶️Answer/Explanation
\( C_2H_4 + Br_2 \rightarrow C_2H_4Br_2 \)
(d) Propene forms poly(propene) in an addition polymerisation reaction. Complete the structure of poly(propene).
▶️Answer/Explanation
(e) Nylon is a polymer made in a condensation polymerisation reaction. Complete the equation to show the formation of nylon.
▶️Answer/Explanation
Question 12 (Sub-topic – P3.1)
A student plans to measure the speed of sound through wood. The student places a microphone at one end of a wooden desk and knocks loudly on the other end of the desk with a hammer. She measures the time it takes for the sound to travel through the desk to the microphone.
(a) It takes 1.5 ms for the sound to travel 6.0 m through the wooden desk. Calculate the speed of sound in wood.
▶️Answer/Explanation
Solution:
The speed of sound can be calculated using the formula:
\[ \text{speed} = \frac{\text{distance}}{\text{time}} \]
Given:
Distance = 6.0 m
Time = 1.5 ms = \(1.5 \times 10^{-3}\) s
\[ \text{speed} = \frac{6.0}{1.5 \times 10^{-3}} = 4000 \, \text{m/s} \]
Therefore, the speed of sound in wood is 4000 m/s.
(b) Explain, in terms of particles, why the speed of sound in wood is much greater than the speed of sound in air.
▶️Answer/Explanation
Solution:
The speed of sound is greater in wood than in air because wood is a solid, and the particles in a solid are much closer together compared to the particles in a gas (like air). In solids, the particles are tightly packed, allowing sound waves to travel more quickly through the material as the vibrations are transferred more efficiently from one particle to the next. In contrast, in air, the particles are far apart, and the transfer of energy between particles is less efficient, resulting in a slower speed of sound.
(c) Sound is an example of a longitudinal wave. State what is meant by a longitudinal wave.
▶️Answer/Explanation
Solution:
A longitudinal wave is a type of wave where the particles of the medium vibrate parallel to the direction of wave propagation. In other words, the particles move back and forth along the same axis as the wave travels. Sound waves are an example of longitudinal waves because the air particles vibrate in the same direction as the sound wave moves.
(d) When a wave travels through a gap similar in size to its wavelength, diffraction occurs. Complete Fig. 12.1 to show diffraction of a sound wave through a doorway.
▶️Answer/Explanation
Solution:
Diffraction is the bending of waves around obstacles or through openings. When a sound wave passes through a doorway (a gap similar in size to its wavelength), the wave spreads out and bends around the edges of the doorway. This results in the sound being heard even in areas that are not directly in line with the doorway. The diagram should show the sound wave spreading out after passing through the doorway, indicating diffraction.