General Instructions
1. This question paper comprises five sections A, B, C, D and E.
2. Section A has 16 questions: Q. No. 1 to 16, Q. No. 3, 7, 10, 12, 14 and 16 are MCQs carrying 1 mark each. Q. No. 4, 8, 11, 13 and 15 are Assertion-Reason type questions carrying 1 mark each. Q. No. 1, 2, 5, 6, 9, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60 are Short Answer questions carrying 2 marks each. Q. No. 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80 are Long Answer questions carrying 3 marks and 5 marks each.
3. Section B contains 13 questions: Q. No. 17 to 29. Q. No. 17, 18, 19, 20, 21, 22, 23 are MCQs carrying 1 mark each. Q. No. 24 is an Assertion-Reason type question carrying 1 mark. Q. No. 25, 26 are Short Answer questions carrying 2 marks each. Q. No. 27, 28, 29 are Long Answer questions carrying 3 marks and 5 marks each.
4. Section C contains 10 questions: Q. No. 30 to 39. Q. No. 30, 31 are MCQs carrying 1 mark each. Q. No. 32 is an Assertion-Reason type question carrying 1 mark. Q. No. 33, 34 are Short Answer questions carrying 2 marks each. Q. No. 35, 36, 37 are Long Answer questions carrying 3 marks each. Q. No. 38, 39 are Long Answer questions carrying 5 marks each.
5. Section D contains 5 Case-based questions carrying 4 marks each. Q. No. 40 and 41 are from Biology, Q. No. 42 and 43 are from Chemistry and Q. No. 44 and 45 are from Physics.
6. Section E contains 5 Long Answer questions carrying 5 marks each. Q. No. 46, 47, 48 are from Biology, Q. No. 49, 50 are from Chemistry, and Q. No. 51, 52 are from Physics.
7. All questions are compulsory. However, internal choice is provided in 2 questions of 2 marks, 2 questions of 3 marks, 2 questions of 5 marks and one Case-based question (last sub-part only) each in Sections A, B, C, D and E.
8. Draw neat diagrams wherever required.
9. Assume suitable values wherever required and state them clearly.
10. Do not use colours in the diagrams unless specifically asked to do so.
ABIOLOGY (30 Marks)
MCQs (1 mark each):
1
Which of the following is an incorrect statement regarding respiration?(a) During exhalation, ribs move inwards and downwards.(b) During inhalation, diaphragm contracts and moves upwards.(c) Exchange of gases takes place in alveoli.(d) Haemoglobin transports oxygen and carbon dioxide.
2
Which of the following plant hormones promotes cell division?(a) Auxin(b) Gibberellin(c) Cytokinin(d) Abscisic acid
3
A student observed the following diagram of a flower's cross-section. Identify the part labelled 'X'.(Diagram showing a flower's cross-section with stamen and pistil labelled. X points to the stigma.)(a) Anther(b) Filament(c) Stigma(d) Ovary
4
Which of the following is a characteristic of asexual reproduction?(a) Involves fusion of gametes.(b) Produces offspring genetically identical to the parent.(c) Leads to greater variation in offspring.(d) Occurs in higher organisms.
5
Which of the following is a non-biodegradable waste?(a) Vegetable peels(b) Paper(c) Plastic bag(d) Cotton cloth
Assertion-Reason Type Questions (1 mark each):
6
Assertion (A): Green plants are called producers.Reason (R): They prepare their own food using light energy.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.
7
Assertion (A): Reflex actions are rapid and involuntary.Reason (R): They involve a simple nerve pathway called a reflex arc, which bypasses the brain for faster processing.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.
Short Answer I (2 marks each):
8
Why is the amount of gas collected in one of the test tubes in the electrolysis of water experiment double that of the other? Name this gas.
9
Explain the importance of DNA copying in reproduction.
10
How does the environment of the womb protect the developing embryo?
Short Answer II (3 marks each):
11
Distinguish between aerobic and anaerobic respiration. Explain why aerobic respiration yields more energy than anaerobic respiration.
12
Explain the process of double circulation in human beings. Why is it necessary?
13
How do organisms that cannot swim or walk obtain their food? Explain with an example.
14
How are the sex of a baby determined in human beings? Explain with the help of a Punnett square if parents have genotype XY and XX.
Case-based Question (4 marks):
15
A student is studying the process of photosynthesis. They set up an experiment as follows: A potted plant with broad leaves was kept in a dark room for 48 hours. Then, one leaf was detached from the plant and its chlorophyll was removed by boiling it in alcohol. After boiling, the leaf was washed and iodine solution was added.(a) What is the purpose of keeping the plant in a dark room for 48 hours?(b) What is the role of chlorophyll in photosynthesis?(c) What would be the observation when iodine solution is added to the leaf and why?
Long Answer (5 marks each):
16
(a) Explain the role of the brain in controlling voluntary and involuntary actions. 3marks(b) How do plants respond to stimuli like light and gravity? Explain the hormones involved. (2 marks)
BCHEMISTRY (25 Marks)
MCQs (1 mark each):
17
Which of the following is an amphoteric oxide?(a) MgO(b) CuO(c) Al2O3(d) SO2
18
The property of self-linking of carbon atoms to form long chains, branched chains and rings is known as:(a) Valency(b) Catenation(c) Isomerism(d) Hybridization
19
Which of the following gases is produced when ethanoic acid reacts with sodium bicarbonate?(a) Hydrogen(b) Carbon dioxide(c) Oxygen(d) Nitrogen
20
Which of the following metals is obtained by the electrolysis of its molten oxide?(a) Copper(b) Iron(c) Aluminium(d) Zinc
21
A solution turns red litmus blue. Its pH is likely to be:(a) 1(b) 4(c) 7(d) 10
22
An alloy is a homogeneous mixture of a metal with a metal or non-metal. Which of the following alloys contains a non-metal as one of its constituents?(a) Brass(b) Bronze(c) Amalgam(d) Steel
23
When copper sulphate solution is electrolyzed using inert electrodes, the substance liberated at the cathode is:(a) Cu(b) H2(c) SO4^2-(d) O2
Assertion-Reason Type Question (1 mark each):
24
Assertion (A): Metals like sodium and potassium react violently with cold water.Reason (R): They are highly reactive metals.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.
Short Answer I (2 marks each):
25
Write balanced chemical equations for the following reactions:(i) Reaction of calcium hydroxide with carbon dioxide.(ii) Reaction of zinc with dilute sulphuric acid.
26
Explain why ionic compounds have high melting and boiling points.
Short Answer II (3 marks each):
27
(a) Name the substance 'X' which is used for whitewashing. Write the reaction of substance 'X' with water. 2marks(b) What is a decomposition reaction? Give one example. (1 mark)
28
Distinguish between a displacement reaction and a double displacement reaction. Give one example of each.
29
What is the difference between roasting and calcination? Explain with one example for each.
Case-based Question (4 marks):
30
A student performed an experiment to study the reaction of metals with metal salt solutions. They took four metals A, B, C, and D and performed displacement reactions with iron sulphate, copper sulphate, zinc sulphate and silver nitrate solutions. The observations were recorded in a table:
| Metal | Iron Sulphate | Copper Sulphate | Zinc Sulphate | Silver Nitrate |
|---|---|---|---|---|
| A | No reaction | Displacement | No reaction | Displacement |
| B | Displacement | Displacement | Displacement | Displacement |
| C | No reaction | No reaction | No reaction | Displacement |
| D | Displacement | Displacement | No reaction | Displacement |
(a) Based on the observations, arrange the metals A, B, C and D in decreasing order of their reactivity. (2 marks)
(b) Write a balanced chemical equation for the reaction that would occur if metal C is added to copper sulphate solution. (1 mark)
(c) Which metal among A, B, C, and D is the least reactive? (1 mark)
Long Answer (5 marks each):
31
(a) Explain the following properties of ionic compounds: (i) Physical nature, (ii) Electrical conductivity. 2marks(b) Identify the type of reaction and write a balanced chemical equation for the following:(i) Iron reacts with copper sulphate.(ii) Burning of natural gas.(iii) Hydrogen reacts with chlorine in the presence of sunlight to form hydrogen chloride. (3 marks)
CPHYSICS (25 Marks)
MCQs (1 mark each):
32
A ray of light passes from medium A to medium B. In medium B, the light ray bends away from the normal. Which of the following statements is true regarding the speed of light in the two media?(a) Speed of light in medium B is greater than in medium A.(b) Speed of light in medium B is less than in medium A.(c) Speed of light is the same in both media.(d) Cannot be determined.
33
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. The position of the object is:(a) At infinity(b) Between the pole and the focus(c) At the focus(d) Beyond the centre of curvature
Assertion-Reason Type Question (1 mark each):
34
Assertion (A): For a normal eye, the least distance of distinct vision is 25 cm.Reason (R): The eye lens needs to adjust its focal length to form a clear image on the retina.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.
Short Answer I (2 marks each):
35
Define the term 'power of a lens'. What is its SI unit? A lens has a power of -2.0 D. What is the focal length of this lens?
36
Explain why the twinkling of stars is due to atmospheric refraction.
Short Answer II (3 marks each):
37
State the laws of refraction of light. Explain with a ray diagram how light refracts through a triangular glass prism.
38
An electric heater rated 1500 W, 220 V is connected to a 220 V mains supply.(a) What is the current drawn by the heater?(b) What is the resistance of the heater?(c) In 2 hours, how much energy is consumed by the heater?
39
(a) Explain Fleming’s Left-Hand Rule with a neat diagram. 2marks(b) Name the device that uses this principle. (1 mark)
Case-based Question (4 marks):
40
A student is studying the magnetic effects of electric current. He sets up an experiment with a straight copper wire connected to a battery, a plug key, and an ammeter in series. He places a compass near the wire and observes the deflection of the compass needle when current flows through the wire.(a) What is the direction of the magnetic field lines around the straight copper wire? (1 mark)(b) How does the direction of the magnetic field change if the direction of current in the wire is reversed? (1 mark)(c) If the student increases the current flowing through the wire, what will be the effect on the magnetic field produced? (1 mark)(d) Name the rule that can be used to determine the direction of the magnetic field around a current-carrying straight conductor. 1mark
Long Answer (5 marks each):
41
(a) Describe the structure of an electromagnet. How can the strength of an electromagnet be increased? 3marks(b) An electric motor is a device that converts electrical energy into mechanical energy. Explain the principle on which it works. (2 marks)
42
(a) Draw a ray diagram to show the formation of a rainbow in the sky. Explain the phenomena involved. 3marks(b) A person is suffering from myopia. Draw a ray diagram to show how spectacles with a concave lens correct this defect. (2 marks)
DCASE-BASED QUESTIONS (16 Marks)
Biology Case-Based (4 marks each):
43
A group of students conducted an experiment to study the process of digestion. They took two test tubes, A and B, each containing 5 ml of boiled rice. 2 ml of saliva was added to test tube A and 2 ml of water was added to test tube B. Both test tubes were kept in a warm place for 30 minutes. Then, a few drops of iodine solution were added to both test tubes.(a) What is the role of saliva in digestion?(b) What is the expected observation in test tube A after adding iodine solution? Give reason.(c) What is the expected observation in test tube B after adding iodine solution? Give reason.
44
Read the passage below and answer the questions that follow:“Environmental pollution is a major concern for the world today. Burning of fossil fuels for energy releases harmful gases into the atmosphere, contributing to air pollution and acid rain. Plastic waste, which is non-biodegradable, accumulates in landfills and pollutes our water bodies. The depletion of the ozone layer, caused by chemicals like CFCs, exposes life on Earth to harmful ultraviolet radiation.”(a) Name one harmful gas released from the burning of fossil fuels that contributes to acid rain.(b) Why is plastic considered a non-biodegradable waste?(c) How does the depletion of the ozone layer affect living organisms?(d) Suggest one method to reduce the problem of plastic waste disposal.
Chemistry Case-Based (4 marks each):
45
A student is studying the properties of acids. They have two solutions, one is dilute hydrochloric acid and the other is sodium hydroxide solution. They perform the following tests:Test 1: The student adds a piece of zinc metal to both solutions. In one solution, effervescence is observed.Test 2: The student adds sodium sulphate solution to both solutions. No visible change is observed in either case.Test 3: The student adds litmus paper to both solutions. One solution turns blue litmus red, while the other turns red litmus blue.(a) Identify the acidic solution and the basic solution. (1 mark)(b) Which solution produces effervescence with zinc metal? Write the balanced chemical equation for the reaction. (2 marks)(c) What is the nature of the salt formed when sodium hydroxide reacts with hydrochloric acid? 1mark
Physics Case-Based (4 marks each):
46
A group of students are experimenting with electrical circuits. They connect an electric bulb to a battery and a plug key. They observe that the bulb glows when the circuit is complete. They then replace the bulb with different materials like a rubber strip, a piece of charcoal, and a metal rod.(a) Which material will allow the electric current to pass through easily? Justify your answer. (1 mark)(b) What is the term used for materials that allow electric current to pass through them? (1 mark)(c) If they connect two 100 W, 220 V bulbs in series to a 220 V supply, will they glow brighter, dimmer or not at all compared to when connected individually? Explain. 2marks
ELONG ANSWER QUESTIONS (20 Marks)
Biology Long Answer (5 marks each):
47
(a) Explain the process of nutrition in amoeba with the help of a labelled diagram. 3marks(b) How are the lungs designed to maximize the surface area for the exchange of gases? (2 marks)
48
(a) Explain the mechanism of sex determination in human beings. 3marks(b) What are the functions of the male reproductive organs? (2 marks)
Chemistry Long Answer (5 marks each):
49
(a) Explain the terms oxidation and reduction with examples. 2marks(b) What are alloys? Why is an alloy of copper and tin used for welding electrical wires whereas pure copper is not? (3 marks)
50
(a) What is meant by homologous series? Give any two characteristics of a homologous series. 2marks(b) Write the IUPAC names and draw the electron dot structures for the following compounds:(i) Ethane (C2H6) (2 marks)(ii) Ethene (C2H4) (1 mark)
Physics Long Answer (5 marks each):
51
(a) State Ohm's law and verify it experimentally with a circuit diagram. 3marks(b) An electric appliance draws a current of 0.2 A when connected to a 220 V line. If the appliance is used for 5 hours daily, calculate the cost of energy to operate it for 30 days at a rate of Rs 4.00 per kWh. (2 marks)
52
(a) Describe the magnetic field produced by a current-carrying circular loop. How does the magnetic field change at the centre of the loop when: (i) the current is increased, (ii) the radius of the loop is increased? 3marks(b) Name the device used to convert mechanical energy into electrical energy and state its principle. (2 marks)
Answer Key
ABIOLOGY
1
(b)
2
(c)
3
(c)
4
(b)
5
(c)
6
(a)
7
(a)
8
Gas collected in one test tube is oxygen (half the amount of hydrogen) and in the other is hydrogen (double the amount of oxygen). This is because water () is decomposed into hydrogen and oxygen during electrolysis. The balanced equation is . Thus, two volumes of hydrogen are produced for every one volume of oxygen.
9
DNA copying ensures that the genetic information is accurately passed from the parent to the offspring, maintaining the characteristics of the species.
10
The amniotic fluid inside the uterus protects the developing embryo from mechanical shocks and injuries. It also helps maintain a constant temperature.
11
Aerobic respiration occurs in the presence of oxygen and produces a large amount of energy (), carbon dioxide, and water. Anaerobic respiration occurs in the absence of oxygen and produces less energy, along with products like ethanol and carbon dioxide (in yeast) or lactic acid (in muscle cells). Aerobic respiration yields more energy because it completely breaks down glucose.
12
Double circulation involves the circulation of blood twice through the heart in one complete cycle. Oxygenated blood from the lungs enters the left atrium, then to the left ventricle, and is pumped to the body. Deoxygenated blood from the body returns to the right atrium, then to the right ventricle, and is pumped to the lungs. This separation ensures efficient oxygen supply to the body tissues.
13
Organisms that cannot move obtain food through parasitic or symbiotic relationships. For example, tapeworms are parasites that live in the intestines of animals and absorb digested food.
14
Sex determination in humans depends on the sex chromosomes. Females have XX chromosomes, and males have XY chromosomes. If the egg (X) is fertilized by an X-carrying sperm, the offspring is female (XX). If the egg (X) is fertilized by a Y-carrying sperm, the offspring is male (XY).Punnett Square:
| X (sperm) | Y (sperm) | |
|---|---|---|
| X (egg) | XX (Female) | XY (Male) |
| X (egg) | XX (Female) | XY (Male) |
| Thus, there is a 50% chance of having a boy and a 50% chance of having a girl. | ||
| 15. (a) To destarch the plant, removing any pre-existing starch. | ||
| (b) Chlorophyll absorbs sunlight, which is the energy source for photosynthesis. | ||
| (c) The part of the leaf where chlorophyll was present will turn blue-black, while the part where chlorophyll was removed will remain brown. This indicates the presence of starch, which is produced during photosynthesis. | ||
| 16. (a) Voluntary actions are controlled by the cerebrum, which is the thinking part of the brain. It receives sensory information and sends signals to muscles to perform coordinated movements like walking, writing, etc. Involuntary actions are controlled by the medulla and cerebellum, which regulate functions like heartbeat, breathing, digestion, and reflexes without conscious thought. | ||
| (b) Plants respond to light (phototropism) by growing towards or away from it, controlled by auxin hormone produced at the shoot tip, which diffuses to the shady side, promoting cell elongation. They respond to gravity (geotropism) by roots growing downwards (positive geotropism) and shoots growing upwards (negative geotropism), influenced by hormones like auxin. |
BCHEMISTRY
17
(c)
18
(b)
19
(b)
20
(c)
21
(d)
22
(d)
23
(a)
24
(a)
25
(i) (ii)
26
Ionic compounds are formed by strong electrostatic forces of attraction between oppositely charged ions. A large amount of energy is required to overcome these strong forces and break the crystal lattice, hence they have high melting and boiling points.
27
(a) Substance 'X' is Calcium oxide (Quicklime), CaO.Reaction: (b) A decomposition reaction is a reaction in which a single compound breaks down into two or more simpler substances. Example:
28
Displacement reaction: A more reactive metal displaces a less reactive metal from its salt solution. Example: .Double displacement reaction: Reaction in which parts of two ionic compounds are exchanged, resulting in the formation of two new compounds. Example: .
29
Roasting: Heating of a sulphide ore in excess of air to convert it into oxide. Example: .Calcination: Heating of a carbonate or hydroxide ore in the absence or limited supply of air to convert it into oxide. Example: .
30
(a) Reactivity Series: B > A > D > C(b) (as C is less reactive than copper)(c) Metal C.
31
(a) (i) Physical nature: Ionic compounds are generally crystalline solids and are hard because of strong inter-ionic forces. They are brittle and break into pieces when pressure is applied.(ii) Electrical conductivity: Ionic compounds do not conduct electricity in the solid state because the ions are held in fixed positions. However, they conduct electricity in molten state or when dissolved in water because the ions are free to move.(b) (i) Displacement reaction: (ii) Combustion reaction: (iii) Combination reaction:
CPHYSICS
32
(a)
33
(b)
34
(b)
35
Power of a lens is the reciprocal of its focal length in metres. Its SI unit is Dioptre (D). Focal length = 1 / Power = 1 / (-2.0 D) = -0.5 m.
36
The atmosphere is made up of different layers of air with varying refractive indices due to changes in temperature. Starlight, on entering the atmosphere, undergoes continuous refraction. The apparent position of the star fluctuates slightly due to these variations, causing the star to appear to twinkle.
37
Laws of refraction:(i) The incident ray, the refracted ray and the normal to the interface of two media at the point of incidence all lie in the same plane.(ii) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. This constant is called the refractive index of the second medium with respect to the first medium. (Snell's Law: )Ray diagram: (Draw a triangular prism with incident ray, refracted ray inside the prism bending towards the normal, and emergent ray bending away from the normal, showing angle of incidence, angle of refraction, angle of emergence and angle of prism).
38
(a) Current, .(b) Resistance, .(c) Energy consumed, . Cost = 3 kWh Rs 4.00/kWh = Rs 12.00.
39
(a) Fleming's Left-Hand Rule states that if the thumb, forefinger, and middle finger of the left hand are held mutually perpendicular to each other, with the forefinger pointing in the direction of the magnetic field and the middle finger pointing in the direction of the current, then the thumb points in the direction of the force acting on the conductor. (Diagram showing three mutually perpendicular fingers representing Force, Field, Current).(b) Electric motor.
40
(a) The magnetic field lines are concentric circles around the straight copper wire.(b) The direction of the magnetic field lines reverses.(c) The magnetic field produced becomes stronger.(d) Right-Hand Thumb Rule.
41
(a) An electromagnet consists of a coil of insulated copper wire wound around a soft iron core. The strength of an electromagnet can be increased by: (i) Increasing the number of turns in the coil. (ii) Increasing the current flowing through the coil. (iii) Using a soft iron core.(b) Principle of electric motor: When a current-carrying conductor is placed in a magnetic field, it experiences a force. This force causes the conductor to move, thus converting electrical energy into mechanical energy.
42
(a) Rainbow formation: A rainbow is formed due to the dispersion of sunlight by tiny water droplets suspended in the atmosphere after a rain shower. The water droplets act like tiny prisms. Sunlight enters the droplet, refracts, undergoes internal reflection, and then refracts again as it emerges. Different colours of light are dispersed at different angles, forming a spectrum. (Diagram showing sunlight entering a raindrop, refracting, reflecting internally, and emerging as a spectrum of colours).(b) Myopia correction: A concave lens is used. The concave lens diverges the light rays slightly before they enter the eye lens. This reduces the overall converging power of the eye lens system, allowing the image of distant objects to be focused on the retina. (Ray diagram showing parallel rays from a distant object, diverging after passing through the concave lens, and then converging on the retina by the eye lens).
DCASE-BASED QUESTIONS
43
(a) Saliva contains the enzyme amylase (or ptyalin) which breaks down starch into simpler sugars like maltose.(b) No significant change will be observed. The boiled rice contains starch, but saliva has broken down most of it into simpler sugars. Therefore, when iodine is added, it will not turn blue-black.(c) The boiled rice in test tube B will turn blue-black when iodine solution is added. This is because water does not contain any digestive enzymes, so the starch in the rice remains undigested.
44
(a) Sulphur dioxide () and nitrogen oxides ().(b) Plastic is non-biodegradable because microorganisms like bacteria and fungi cannot break down its complex chemical structure into simpler substances.(c) The depletion of the ozone layer exposes life on Earth to harmful ultraviolet (UV) radiation, which can cause skin cancer, damage eyes, and harm ecosystems.(d) (Any one) Use reusable bags instead of plastic bags, recycle plastic waste, use biodegradable alternatives to plastic.
45
(a) Acidic solution: The one that turns blue litmus red. Basic solution: The one that turns red litmus blue.(b) The acidic solution (dilute hydrochloric acid) will produce effervescence with zinc metal.
(c) The salt formed is sodium chloride (NaCl), which is a neutral salt.
46
(a) The charcoal (or a metal rod) will allow electric current to pass through easily because it is a conductor. Charcoal is a conductor of electricity due to the presence of free electrons. Metals are also good conductors. Rubber is an insulator and will not allow current to pass.(b) Conductors.(c) The bulbs will glow dimmer. When connected in series, the total resistance increases. Since the voltage is divided between the two bulbs, the power consumed by each bulb (and hence their brightness) will be less than when connected individually to the same voltage source.
ELONG ANSWER QUESTIONS
47
(a) Nutrition in Amoeba: Amoeba takes in food using temporary finger-like extensions of the cell surface called pseudopodia, which fuse together to form a food vacuole. The food vacuole contains food particles. Digestive juices secreted inside the food vacuole digest the food. The digested food is absorbed by the cytoplasm. Undigested food is expelled outside by the action of the vacuole by the process of exocytosis. (Diagram showing phagocytosis, formation of food vacuole, digestion, absorption and egestion).(b) Lungs are designed to maximize the surface area for gas exchange by having a large number of tiny air sacs called alveoli. These alveoli provide a vast surface area (about 70-100 in adults) within a compact space. The walls of the alveoli are very thin (one-cell thick) and are surrounded by a dense network of blood capillaries, facilitating rapid diffusion of oxygen and carbon dioxide.
48
(a) Sex determination in human beings is genetically controlled. Females have XX chromosomes, while males have XY chromosomes. During reproduction, females produce eggs with only an X chromosome. Males produce sperms, half of which carry an X chromosome and the other half carry a Y chromosome. If a sperm carrying an X chromosome fertilizes the egg, the resulting zygote will be XX (female). If a sperm carrying a Y chromosome fertilizes the egg, the zygote will be XY (male).(b) Functions of male reproductive organs:Testes: Produce male gametes (sperms) and male sex hormone (testosterone).Seminal vesicles and prostate gland: Secrete fluids that help in the transport of sperms and provide nutrition.Vas deferens: Tube that carries sperms from the testes.Penis: External male reproductive organ responsible for delivering sperms into the female reproductive tract.
49
(a) Oxidation: A reaction in which a substance gains oxygen or loses hydrogen. Example: . Here, copper is oxidized to copper oxide.Reduction: A reaction in which a substance loses oxygen or gains hydrogen. Example: . Here, Zinc oxide is reduced to zinc.(b) Alloys are homogeneous mixtures of metals with other elements (metals or non-metals) to improve their properties. An alloy of copper and tin (bronze) is used for welding electrical wires because it has a lower melting point than pure copper, making it easier to melt and form a strong joint. Pure copper, while an excellent conductor, has a high melting point which makes welding difficult.
50
(a) A homologous series is a group of organic compounds that have the same functional group and similar chemical properties, and successive members differ by a group.Characteristics:(i) They have the same functional group.(ii) Successive members differ by a unit.(iii) Their physical properties show a gradual change with increasing molecular mass.(b) (i) Ethane ()Electron dot structure:
(ii) Ethene ()
Electron dot structure:
51
(a) Ohm's Law: It states that the potential difference (V) across the ends of a conductor is directly proportional to the current (I) flowing through it, provided the temperature and other physical conditions remain unchanged. , so , where R is the resistance of the conductor.Experimental Verification: (Circuit diagram showing a battery, plug key, rheostat, ammeter, resistor, and voltmeter connected in series/parallel as appropriate. Steps involved: Take readings of V and I for different values of current by adjusting the rheostat. Plot a graph of V vs I. The graph will be a straight line passing through the origin, confirming Ohm's law.)(b) Power, .Energy consumed per day = .Energy consumed in 30 days = .Cost = .
52
(a) Magnetic field of a circular loop: The magnetic field lines inside the loop are approximately straight and parallel to the axis of the loop. Outside the loop, the field lines spread out and resemble those of a bar magnet.(i) If the current is increased, the magnetic field strength increases.(ii) If the radius of the loop is increased (keeping current and number of turns the same), the magnetic field strength at the centre decreases.(b) Device: Electric generator. Principle: Electromagnetic induction – when a conductor is placed in a magnetic field and rotated or moved, an electromotive force (e.m.f.) is induced in the conductor, causing an electric current to flow if the circuit is closed.
