Brain Grain · braingrain.in
Science — Practice Paper · Set 1
Class: 10Samacheer KalviMax Marks: 86
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 15 × 1 = 15
Choose the correct answer. (Answer all questions.)
1.When sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound remain the same. Do you hear an echo sound on a hotter day? Justify your answer.[1]
2.The hydroxide ion concentration of a solution is 1 \times 10-11M. What is the pH of the solution?[1]
3.Will the cool drinks give more fizz at top of the hills or at the foot? Explain[1]
4.Where do the light dependent reaction and the Calvin cycle occur in the chloroplast?[1]
5.Transpiration is a necessary evil in plants. Explain.[1]
6.Read the following passage and answer the questions that follow[1]
7.The eyes of the nocturnal birds like owl are having a large cornea and a large pupil. How does it help them?[1]
8.What precautions can be taken for preventing heart diseases ?[1]
9.“Wearing helmet and fastening the seat belt is highly recommended for safe journey” Justify your answer using Newton’s laws of motion.[1]
10.Cell phone towers should be placed far away from residential areas. Why?[1]
11.An organic compound ‘A’ is widely used as a preservative and has the molecular formula C2H4O2. This compound reacts with ethanol to form a sweet smelling compound ‘B’.[1]
12.‘A’ is a cylindrical structure that begins from the lower end of medulla and extend downwards. It is enclosed in bony cage ‘B’ and covered by membranes ‘C’. As many as ‘D’ pairs of nerves arise from the structure ‘A’. (i) What is A? (ii) Name (a) bony cage ‘B’ and (b) membranes ‘C’ (iii) How much is D?[1]
13.Our body contains a large number of cells ‘L’ which are the longest cells in the body. L has long and short branch called as ‘M’ and ‘N’ respectively. There is a gap ‘O’ between two ‘L’ cells, through which nerve impulse transfer by release of chemical substance ‘P’. (i) Name the cells L (ii) What are M and N? (iii) What is the gap O? (iv) Name the chemical substance P[1]
14.List any three activities based on 3R approach to conserve natural resources.[1]
15.Calculate the % relative abundance of B -10 and B -11, if its average atomic mass is 10.804 amu.[1]
Part II — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
16.Self-pollination[2]
17.Draw and label the structure of oxysomes.[2]
18.Sanjay is sitting in the exam hall. Before the start of the exam , he sweats a lot, with increased rate of heart beat. Why does this condition occur?[2]
19.Name the hormone responsible for the vigorous contractions of the uterine muscles.[2]
20.Why is the circulation in man referred to as double circulation?[2]
21.The inputs are CO2 from the atmosphere and ATP and NADPH2 from the light reaction. The end product is glucose.[2]
22.The thunder of cloud is heard 9.8 seconds later than the flash of lightning. If the speed of sound in air is 330 m s-1, what will be the height of the cloud?[2]
23.Mass is a scalar quantity[2]
24.Write the characteristics of insect pollinated flowers.[2]
25.What is the need for contraception ?[2]
26.The hybrids are stronger and vigorous than their parents. : 2. It helps to accumulate superior genes and eliminate undesirable genes.[2]
27.Two observers are stationed in two boats 4.5 km apart. A sound signal sent by one, under water, reaches the other after 3 seconds. What is the speed of sound in the water?[2]
28.Name the conditions when both the alleles are identical?[2]
29.How are e-wastes generated?[2]
30.If one pollen grain produces two male gametes, how many pollen grains are needed to fertilize 10 ovules?[2]
31.Name the endocrine glands associated with kidneys.[2]
32.Why did Mendel select pea plant for his experiments?[2]
33.How can menstrual hygiene be maintained during menstrual days?[2]
Part III — Long Answer Questions 7 × 5 = 35
Answer in detail. (Answer all questions.)
34.Explain the types of double displacement reactions with examples.[5]
35.Why is it not possible to use solar cells to meet our energy needs? State three reason to support to your answer.[5]
36.What are the factors that affect the speed of sound in gases?[5]
37.How do detergents cause water pollution? Suggest remedial measures to prevent this pollution?[5]
38.What are the types of inertia? Give an example for each type.[5]
39.a) What happens when MgSO4.7H2O is heated? Write the appropriate equation b) Define solubility[5]
40.Define moment of a couple.[5]
🔑 Show Answer Key — Set 1
- 1. On a hotter day, the speed of sound increases, so the echo returns in a shorter time: t = 2d/v. If the fixed distance is just enough for an echo on a cooler day, the return time may fall below 0.1 s and the echo will not be heard distinctly. If the reflecting surface is far enough that t remains at least 0.1 s, the echo can still be heard.
- 2. [OH-] = 1 x 10^-11 M pOH = -log10[OH-] = 11 pH + pOH = 14 pH = 14 - 11 = 3
- 3. Cool drinks will fizz more at the top of the hill. At higher altitude, pressure is lower, so the solubility of carbon dioxide in the drink decreases and more CO2 escapes as bubbles.
- 4. (i) The light dependent reaction refers to the light reaction of photosynthesis or Hill reaction and occurs in the grana of chloroplast. (ii) The Calvin cycle occurs in the stroma of chloroplast. ---
- 5. Transpiration, the process of water vapor loss from a plant's aerial parts, is often described as a 'necessary evil' because it is essential for plant survival and function, yet it also poses a risk of dehydration. It is necessary because it drives the ascent of sap, enabling the transport of water and dissolved mineral nutrients from the roots to the leaves, which is vital for photosynthesis and growth. Transpiration also plays a role in cooling the plant surface, preventing overheating, and helps maintain turgor pressure in cells, supporting leaf expansion and plant rigidity. However, it is considered an 'evil' because it leads to significant water loss. In conditions of water scarcity or drought, excessive transpiration can cause wilting, reduce photosynthetic efficiency, stunt growth, and, in severe cases, lead to the death of the plant. Therefore, plants must balance the benefits of transpiration with the risk of water loss.
- 6. (a) Menarche — the first menstruation. Typical onset about 11–15 years (commonly 11–13 years but varies). (b) Napkin hygiene measures: use clean sanitary pads or tampons; change pads every 4–6 hours (or more often if needed); wash external genital area with mild soap and water and dry; wash hands before and after changing pads; wrap used pads in paper/plastic and dispose in bin or use napkin incinerator — do not flush; do not reuse disposable pads; store pads hygienically. (c) Yes. Rahini was correct — such advertisements raise awareness about menstrual hygiene and safe products.
- 7. The eyes of nocturnal birds like owls are adapted to see in low light conditions. A large cornea, which is the transparent outer layer of the eye, allows a greater amount of light to enter. Similarly, a large pupil, the opening in the center of the iris, can expand significantly to let in even more light. This increased light gathering capacity ensures that more light reaches the retina, where photoreceptor cells convert it into neural signals. Consequently, the bird can form a brighter and clearer image of its surroundings, enabling it to hunt and navigate effectively in the dim light of night.
- 8. Diet: reduce total calories if overweight; limit saturated fats and trans fats and dietary cholesterol; include moderate polyunsaturated and monounsaturated fats; reduce salt (sodium); eat more fruits, vegetables, whole grains and dietary fiber. Lifestyle: regular physical activity (daily exercise/walking), maintain healthy weight. Avoid smoking and excessive alcohol. Regular medical checkups to monitor blood pressure and blood cholesterol.
- 9. 1) State laws used: Newton's 1st law (inertia) and 2nd law (F = ma) plus impulse-momentum (Delta p = F_avg Delta t). 2) Describe the hazard: In a sudden stop or collision passenger's velocity v must change to zero (Delta v = -v); momentum change Delta p = mDelta v. 3) Use formula: average stopping force F_avg = mDelta v/Delta t. For fixed m and Delta v, larger Delta t -> smaller F_avg. 4) Apply to helmet: helmet cushions impact, increases Delta t and impact distance, so F_avg on skull decreases -> less injury. 5) Apply to seat belt: seat belt applies the unbalanced force to decelerate passenger, increases effective Delta t and spreads force across torso, preventing ejection and reducing localized injuries. 6) Units reminder: mass (kg), velocity (m/s), force (N = kg m/s2), impulse (N s). Example (optional): A 70 kg person at 20 m/s (72 km/h) stopped in 0.05 s -> F_avg approx. 70x20/0.05 = 28,000 N; if stopping time increases to 0.5 s with restraint/cushioning -> F_avg approx. 2,800 N, a tenfold reduction in average force.
- 10. Cell phone towers emit radio-frequency electromagnetic waves. To reduce continuous exposure and possible health concerns, they should be placed away from densely populated residential areas.
- 11. (i) Compound A is ethanoic acid (acetic acid), CH3COOH. (ii) It reacts with ethanol in the presence of concentrated H2SO4 to form the sweet-smelling ester ethyl ethanoate, B: CH3COOH + C2H5OH --conc. H2SO4-> CH3COOC2H5 + H2O (iii) The process is esterification.
- 12. (i) A – Spinal cord. (ii)(a) B – Vertebral column (b) C – Meninges. (iii) D – 31 pairs of spinal nerves.
- 13. (i) The cells referred to as L, which are the longest cells in the body and are fundamental to the nervous system, are neurons. (ii) M represents the axon, which is the long branch extending from the neuron's cell body, responsible for transmitting nerve impulses away from the cell. N represents the dendrites, which are the shorter, branching extensions that receive nerve impulses from other neurons and transmit them towards the cell body. (iii) The gap O between two neurons, across which nerve impulses are transmitted, is called a synapse. (iv) The chemical substance P released at the synapse to transfer the nerve impulse is a neurotransmitter, specifically acetylcholine in many cases.
- 14. (i) Reduce use of natural resources. E.g: coal. (ii) Reuse the waste whenever possible. Example water from kitchens can be used for growing plants. (iii) Recycle materials wherever possible. Example (a) Use of treated sewage water for gardening. (b) Bio wastes to be made into compost. ---
- 15. Let the percentage abundance of B-10 be x and B-11 be 100 - x. Average atomic mass = [10.01294x + 11.009305(100 - x)]/100 = 10.804. Solving, x = 20.636%. Therefore B-10 = 20.636% and B-11 = 79.364%.
- 16. Self-pollination (autogamy): Transfer of pollen grains from the anther to the stigma of the same flower or to the stigma of another flower on the same plant. Example: Pea, wheat, rice, tomato. <div
- 17. Oxysomes are the small knob-like F1 particles present on the inner mitochondrial membrane or cristae. A labelled diagram should show the mitochondrial outer membrane, inner membrane, cristae, matrix, stalk and the knob-like oxysome/F1 particle. Oxysomes contain enzymes needed for ATP synthesis during respiration.
- 18. This condition occurs due to the body's 'fight or flight' response, typically triggered by stress or fear. When Sanjay perceives the exam as a stressful situation, his sympathetic nervous system is activated. This activation signals the adrenal medulla to rapidly secrete adrenaline, also known as epinephrine. Adrenaline is a hormone that prepares the body for intense physical activity by increasing the heart rate, raising blood pressure, and diverting blood flow to muscles. Simultaneously, the sympathetic nervous system stimulates the sweat glands, leading to increased perspiration, which helps to cool the body down in anticipation of exertion. These physiological changes collectively contribute to the feeling of anxiety and the physical symptoms experienced before a high-stakes event like an exam. <div
- 19. The hormone responsible for inducing and strengthening the vigorous contractions of the uterine muscles during childbirth is oxytocin. Oxytocin is a peptide hormone produced by the hypothalamus and released by the posterior pituitary gland. Its release is stimulated by the stretching of the cervix and uterus during labor. These powerful contractions are essential for dilating the cervix and pushing the baby out of the uterus during the delivery process. Oxytocin also plays a role in the milk let-down reflex during breastfeeding.
- 20. Circulation in humans is referred to as double circulation because the blood passes through the heart twice during one complete circuit of the body. This system involves two distinct circulatory pathways: the pulmonary circulation and the systemic circulation. In pulmonary circulation, deoxygenated blood is pumped from the right side of the heart to the lungs, where it gets oxygenated, and then returns to the left side of the heart. In systemic circulation, oxygenated blood is pumped from the left side of the heart to the rest of the body, delivering oxygen and nutrients, and deoxygenated blood returns to the right side of the heart. This double circulation ensures that oxygenated and deoxygenated blood do not mix, which is crucial for efficient oxygen delivery to the tissues and maintaining a high metabolic rate.
- 21. The Calvin cycle, often referred to as the dark reaction of photosynthesis, is a complex biochemical pathway that takes place in the stroma of chloroplasts. The primary inputs for this cycle are carbon dioxide (CO2) absorbed from the atmosphere, and the energy-carrying molecules ATP and NADPH, which are produced during the light-dependent reactions. Through a series of enzyme-catalyzed reactions, these inputs are used to reduce CO2 and ultimately synthesize glucose (C6H12O6), the main carbohydrate end product that fuels the plant's growth and metabolic activities. HOT IX. Higher Order Thinking 3 marks each <div
- 22. Light travels much faster than sound, so the delay is due to sound. Height of cloud = speed x time = 330 x 9.8 = 3234 m.
- 23. Mass is a scalar quantity because it is defined solely by its magnitude and does not possess any direction. It represents the amount of matter present in a body. Unlike vector quantities, which require both magnitude and direction for their complete description, mass only needs a numerical value and a unit. The SI unit of mass is the kilogram (kg). Being a scalar quantity, mass can be added or subtracted using simple arithmetic rules, making calculations involving mass straightforward.
- 24. Insect-pollinated flowers, a process known as entomophily, exhibit several distinct characteristics to attract insects and facilitate pollen transfer. These flowers are typically large, brightly colored, and often possess a strong, pleasant fragrance to lure insects like bees, butterflies, and flies. They also produce nectar, a sugary liquid, which serves as a reward for the visiting insects. The pollen grains themselves are usually larger, heavier, and have a rough or spiny outer surface (exine) that helps them adhere to the bodies of insects, ensuring effective transport to the stigma of another flower. The stigma is often sticky to readily capture the pollen carried by insects.
- 25. Contraception is essential for several vital reasons related to individual health, family well-being, and societal development. Firstly, it helps prevent unwanted pregnancies, giving individuals and couples control over their reproductive choices and family size. Secondly, effective contraception contributes significantly to controlling population growth, which can alleviate pressure on resources and the environment. Thirdly, it allows for the spacing of births, which is crucial for the health of both the mother and the child, enabling adequate recovery time for the mother and proper care for each child. Lastly, certain contraceptive methods, particularly barrier methods, can help reduce the transmission of sexually transmitted infections (STIs), thereby promoting sexual health.
- 26. 1. Heterosis (hybrid vigour): hybrids are stronger and more vigorous than their parents. 2. Selection: it helps accumulate superior genes and eliminate undesirable genes during breeding.
- 27. Distance = 4.5 km = 4500 m and time = 3 s. Speed of sound in water v = d/t = 4500/3 = 1500 m s-1 = 1.5 km s-1.
- 28. Homozygous condition.
- 29. E-wastes are generated when electrical and electronic devices (like mobiles, computers, TVs, refrigerators) become spoiled, outdated or non-repairable and are discarded by households, offices, industries, hospitals and institutions. Rapid technological change, short product life, lack of repair and mass disposal increase e-waste generation.
- 30. 10 pollen grains.
- 31. The endocrine glands associated with the kidneys are the adrenal glands, also known as suprarenal glands. These glands are situated on top of each kidney. The adrenal glands are composed of two distinct parts: the outer adrenal cortex and the inner adrenal medulla. The adrenal cortex produces steroid hormones like aldosterone, which regulates salt and water balance, and cortisol, which is involved in stress response and metabolism. The adrenal medulla produces catecholamine hormones, primarily adrenaline (epinephrine) and noradrenaline (norepinephrine), which are crucial for the 'fight or flight' response.
- 32. (i) It is naturally self-pollinating and so is very easy to raise pure breeding individuals. (ii) It has a short life span as it is an annual and so it was possible to follow several generations. (iii) It is easy to cross-pollinate. (iv) It has deeply defined contrasting characters. (v) The flowers are bisexual.
- 33. (i) Sanitary pads should be changed regularly, to avoid infections due to microbes from vagina and sweat from genitals. (ii) Use of warm water to clean genitals helps to get rid of menstrual cramps. (iii) Wearing loose clothing rather than tight- fitting clothes will ensure the airflow around the genitals and prevent sweating.
- 34. Types of double displacement reactions: (i) Precipitation reaction: Two aqueous ionic solutions react to form an insoluble salt, called a precipitate. Pb(NO3)2(aq) + 2KI(aq) -> PbI2(s) + 2KNO3(aq) (ii) Neutralization reaction: An acid reacts with a base to form salt and water. HCl(aq) + NaOH(aq) -> NaCl(aq) + H2O(l) (iii) Gas-evolution reaction: The reaction produces a gas that escapes. Na2CO3(aq) + 2HCl(aq) -> 2NaCl(aq) + H2O(l) + CO2(g)
- 35. Three reasons: (1) Intermittency — solar energy is not available at night and varies with weather, requiring storage. (2) High initial cost and current conversion efficiency limits — solar cells have significant upfront cost and limited efficiency. (3) Large area and storage needs — meeting high energy demand requires large panel area and storage/battery systems, increasing cost and complexity.
- 36. (i) Effect of density: Velocity of sound in a gas is inversely proportional to the square root of density, so it decreases as density increases. (ii) Effect of temperature: Velocity of sound in a gas increases with temperature. For air, vT = v0 + 0.61T, where v0 = 331 m s-1 at 0°C. (iii) Effect of relative humidity: When humidity increases, the speed of sound increases because humid air has lower effective density than dry air.
- 37. Some detergents cause water pollution because they contain branched hydrocarbon chains which are not easily biodegradable. These persistent detergents remain in water bodies, leading to the formation of persistent foam and a significant reduction in water quality. Furthermore, certain detergents contain phosphates, which act as nutrients for aquatic plants. An excessive amount of phosphates can lead to eutrophication, characterized by rapid growth of algae (algal blooms). When these algae die and decompose, they consume large amounts of dissolved oxygen in the water, creating hypoxic conditions that are harmful or fatal to fish and other aquatic life. To prevent this pollution, remedial measures include using biodegradable detergents with straight-chain hydrocarbon structures, opting for phosphate-free detergent formulations, using detergents only in the required quantities, treating wastewater effectively before its discharge into natural water bodies, and avoiding the release of untreated detergent-laden water into rivers and lakes.
- 38. (i) Inertia of rest: The resistance of a body to change its state of rest. Example: Leaves on a tree tend to remain at rest when the branch is shaken; they may get detached and fall. (ii) Inertia of motion: The resistance of a body to change its state of motion. Example: An athlete runs before jumping-the forward motion helps the athlete travel a longer distance in the jump. (iii) Inertia of direction: The resistance of a body to change its direction of motion. Example: When a car makes a sharp turn, passengers tend to be thrown outward or lean sideways because their bodies tend to continue in the original straight-line motion.
- 39. a) When magnesium sulphate heptahydrate crystals are gently heated, they lose seven water molecules and become anhydrous magnesium sulphate. MgSO4.7H2O (s) -> MgSO4 (s) + 7H2O (g) b) Solubility is the number of grams of solute that can dissolve in 100 g of solvent to form a saturated solution at a given temperature. $Solubility = [ Mass of the solute / Mass of the solvent ] \times 100$
- 40. Derivation: Let two equal and opposite parallel forces +F and -F be separated by perpendicular distance d. Each force produces a torque about any point; the net torque (moment of couple) is M = F x d. Unit: N m. Example: If F = 10 N and d = 0.20 m, then M = 10 x 0.20 = 2.0 N m (rotational tendency).
Brain Grain · braingrain.in
Science — Practice Paper · Set 2
Class: 10Samacheer KalviMax Marks: 86
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 15 × 1 = 15
Choose the correct answer. (Answer all questions.)
1.How is the digestive system of rabbit suited for herbivorous mode of feeding?[1]
2.A piece of wire of resistance 10 ohm is drawn out so that its length is increased to three times its original length. Calculate the new resistance.[1]
3.a) Identify the bond between H and F in HF molecule.[1]
4.Explain the experiment of measuring the real and apparent expansion of a liquid with a neat diagram.[1]
5.Octopus, cockroach and frog all have eyes. Can we group these animals together to establish a common evolutionary origin. Justify your answer.[1]
6.While doing an experiment for the determination of focal length of a convex lens, Raja Suddenly dropped the lens. It got broken into two halves along the axis. If he continues his experiment with the same lens, (a) can he get the image? (b) Is there any change in the focal length?[1]
7.‘P’ is a gene required for the synthesis of vitamin A. It is integrated with genome of ‘Q’ to produce genetically modified plant ‘R’.[1]
8.Susan’s father feels very tired and frequently urinates. After clinical diagnosis he was advised to take an injection daily to maintain his blood glucose level. What would be the possible cause for this? Suggest preventive measures.[1]
9.Under which conditions does the law of independent assortment hold good and why?[1]
10.When sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound remain the same. Do you hear an echo sound on a hotter day? Justify your answer.[1]
11.The hydroxide ion concentration of a solution is 1 \times 10-11M. What is the pH of the solution?[1]
12.Will the cool drinks give more fizz at top of the hills or at the foot? Explain[1]
13.Where do the light dependent reaction and the Calvin cycle occur in the chloroplast?[1]
14.Transpiration is a necessary evil in plants. Explain.[1]
15.Read the following passage and answer the questions that follow[1]
Part II — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
16.Calculate the % of each element in calci-um carbonate. (Atomic mass: C-12, O-16, Ca -40)[2]
17.It forms the grey matter of the brain[2]
18.What is collateral vascular bundle?[2]
19.Cambium : Absent[2]
20.Explain the dark reaction (Calvin cycle) by which CO2 is reduced into carbohydrates using ATP and NADPH.[2]
21.The inputs are water, solar energy, photosynthetic pigments. The end products are ATP and NADPH2.[2]
22.Actions performed without our control are called involuntary actions.[2]
23.Name the part of the human female reproductive system where the following occurs.[2]
24.Arjun is studying in tenth standard. He was down with fever and went to meet the doctor. As he went to the clinic he saw a patient undergoing treatment for severe leech bite. Being curious, Arjun asked the doctor why leech bite was not felt as soon as it attaches to the skin ? What would have been the reply given by the doctor?[2]
25.Identify the parts A, B, C and D[2]
26.Give an account on vascular bundle of dicot stem.[2]
27.A convex lens produces mostly real images[2]
28.What are Okazaki fragments?[2]
29.State Ohm’s law.[2]
30.What will happen if trees are cut down?[2]
31.Why is the teeth of rabbit called heterodont?[2]
32.Also called longitudinal expansion[2]
33.Glucose is broken down into carbon dioxide, water and energy.[2]
Part III — Long Answer Questions 7 × 5 = 35
Answer in detail. (Answer all questions.)
34.Calculate the coefficient of cubical expansion of a zinc bar. Whose volume is increased 0.25 m3 from 0.3 m3 due to the change in its temperature of 50 K.[5]
35.Why are traffic signals red in colour?[5]
36.Movement is again down a potential gradient.[5]
37.Imprints of fossils tell us about evolution-How?[5]
38.In angiosperms the pollen germinates to produce pollen tube that carries two gametes. What is the purpose of carrying two gametes when single gamete can fertilize the egg?[5]
39.Give the applications of universal law gravitation.[5]
40.How does fossilization occur in plants?[5]
🔑 Show Answer Key — Set 2
- 1. The digestive system of a rabbit is highly adapted for its herbivorous diet, which primarily consists of fibrous plant material. Key adaptations include specialized dentition and a significantly enlarged caecum. Rabbits possess heterodont dentition, meaning they have different types of teeth suited for their diet, although they lack canine teeth. Their incisors are prominent for gnawing, followed by a gap called the diastema, which facilitates chewing and manipulation of food. The large, well-developed caecum is a crucial component where microbial fermentation occurs. This fermentation process, carried out by bacteria and other microorganisms, breaks down cellulose, a complex carbohydrate found in plant cell walls that rabbits cannot digest on their own. The caecum's structure and the presence of these symbiotic microbes allow rabbits to extract maximum nutrients from their fibrous food. Following caecal fermentation, rabbits practice coprophagy, re-ingesting soft fecal pellets (caecotrophes) to absorb the nutrients produced during fermentation, further enhancing nutrient assimilation.
- 2. Given initial R = 10 Ω. Let initial length = L and area = A. R = ρL/A = 10 Ω. New length = 3L. With constant volume, new area = A/3. R' = ρ(3L)/(A/3) = 9 (ρL/A) = 9R = 9 x 10 Ω = 90 Ω.
- 3. a) The bond between H and F in the HF molecule is a polar covalent bond. b) This identification is based on the significant difference in electronegativity between hydrogen and fluorine. Fluorine is highly electronegative, while hydrogen is less electronegative. This unequal sharing of electrons creates a partial positive charge on the hydrogen atom and a partial negative charge on the fluorine atom, resulting in a polar bond. c) Electronegativity generally increases from left to right across a period in the periodic table due to an increasing nuclear charge and a decrease in atomic radius. Conversely, electronegativity decreases as one moves down a group because the atomic radius increases and the outermost electrons are farther from the nucleus, experiencing less attraction.
- 4. Apparatus: small flask (or bulb) fitted with a narrow capillary tube, wooden or metal stand, scale/ruled glass behind the capillary (for marking heights), thermometer, burner. Procedure: 1. Fill the flask with the liquid up to a mark on the capillary and glass scale. Mark the initial level as L1 at room temperature and note the initial temperature T1. 2. Heat the flask gently. As the vessel (container) expands its internal volume increases and the liquid level in the capillary may fall slightly. When this fall is observed, mark this level as L2. 3. Continue heating so the liquid itself expands; the liquid level then rises and finally stabilises at L3 for a higher temperature T2. Observations and definitions: - Apparent expansion of the liquid = observed change relative to the original mark = L3 - L1. - Real (actual) expansion of the liquid = change of liquid level excluding container expansion = L3 - L2. - Therefore: Real = Apparent + (L1 - L2), where (L1 - L2) represents the change due to container expansion (drop in level). Relation between coefficients: - Let γ_liquid be the coefficient of cubical expansion of the liquid, γ_container that of the container, and γ_apparent the apparent coefficient observed. - γ_apparent = γ_liquid - γ_container. - Since the container is a solid, γ_container approx. 3α (α is the linear coefficient of the container). - Hence γ_liquid = γ_apparent + 3α. Formulas for a temperature change Delta T = (T2 - T1): - Real volume increase Delta V_real = V0 γ_liquid Delta T. - Apparent volume increase Delta V_apparent = V0 (γ_liquid - γ_container) Delta T. Notes for exam answers: - Label the neat diagram: flask/bulb, capillary tube, scale, L1, L2, L3, thermometer, burner. - Give units: coefficients in °C^-1 (per degree Celsius) and volume in m3 (or cm3) when needed. - State conclusion: real expansion of a liquid is greater than its apparent expansion because the container also expands.
- 5. No. They cannot be grouped solely on presence of eyes. Correct classification: octopus — phylum Mollusca (Cephalopoda); cockroach — phylum Arthropoda (Insecta); frog — phylum Chordata (Amphibia).
- 6. (a) Yes, he can still get the image using one half of the broken convex lens. (b) There is no change in the focal length because the curvature of the lens surfaces does not change. However, the intensity or brightness of the image will be reduced because less light passes through the broken lens.
- 7. P = gene(s) for provitamin A (beta‑carotene biosynthesis; e.g., psy and crtI). Q = the crop plant whose genome is modified (example: rice). R = the genetically modified plant (Golden Rice) that produces beta‑carotene (provitamin A) in edible tissues.
- 8. Susan's father is likely suffering from diabetes mellitus, a condition characterized by persistently high blood glucose levels. This can occur due to insufficient production or utilization of insulin, a hormone produced by the beta cells of the pancreas. The fact that he requires daily insulin injections suggests he has insulin-dependent diabetes, also known as Type 1 diabetes, where the pancreatic beta cells may have been destroyed or are not functioning properly. The symptoms of tiredness and frequent urination are classic signs of hyperglycemia (high blood sugar), as the body attempts to excrete excess glucose through urine, leading to dehydration and fatigue. While Type 1 diabetes cannot be definitively prevented, it can be effectively managed through regular insulin therapy, consistent monitoring of blood glucose levels, a carefully balanced diet, regular physical activity, and diligent medical follow-up. Maintaining a healthy body weight, engaging in regular exercise, and controlling sugar intake are also crucial for preventing or managing Type 2 diabetes, a related but distinct condition. 🎒 Brain Grain Revision Challenge Study Smarter, Score Higher. Revise this Samacheer Class 10 Science topic, then continue with the Revision Challenge. Free Revision Daily Revision Exam Practice XP Challenge AI Doubt Help Start Revision Challenge 🏆 Revision Challenge ← Previous Ch.15 Nervous System Next → Ch.17 Reproduction in Plants and Animals 📅 One free practice question, every morning Join the free WhatsApp challenge — a quick question daily to build your study streak. No signup. Join free → More Class 10 Science chapters Chapter Chapter Chapter Chapter Chapter Chapter <a style="color:var(--leaf-dark,#08755f);font-weight:600;font-size:.9rem;text-decoration:none;padding:0;border-radius:0;display:inline" href="/samacheer-class-10
- 9. The law of independent assortment holds when the genes for the two traits are on different (non‑homologous) chromosomes or are far apart on the same chromosome (not linked), each trait is controlled by a pair of alleles that segregate during gamete formation, and there is no interaction or linkage between the genes.
- 10. On a hotter day, the speed of sound increases, so the echo returns in a shorter time: t = 2d/v. If the fixed distance is just enough for an echo on a cooler day, the return time may fall below 0.1 s and the echo will not be heard distinctly. If the reflecting surface is far enough that t remains at least 0.1 s, the echo can still be heard.
- 11. [OH-] = 1 x 10^-11 M pOH = -log10[OH-] = 11 pH + pOH = 14 pH = 14 - 11 = 3
- 12. Cool drinks will fizz more at the top of the hill. At higher altitude, pressure is lower, so the solubility of carbon dioxide in the drink decreases and more CO2 escapes as bubbles.
- 13. (i) The light dependent reaction refers to the light reaction of photosynthesis or Hill reaction and occurs in the grana of chloroplast. (ii) The Calvin cycle occurs in the stroma of chloroplast. ---
- 14. Transpiration, the process of water vapor loss from a plant's aerial parts, is often described as a 'necessary evil' because it is essential for plant survival and function, yet it also poses a risk of dehydration. It is necessary because it drives the ascent of sap, enabling the transport of water and dissolved mineral nutrients from the roots to the leaves, which is vital for photosynthesis and growth. Transpiration also plays a role in cooling the plant surface, preventing overheating, and helps maintain turgor pressure in cells, supporting leaf expansion and plant rigidity. However, it is considered an 'evil' because it leads to significant water loss. In conditions of water scarcity or drought, excessive transpiration can cause wilting, reduce photosynthetic efficiency, stunt growth, and, in severe cases, lead to the death of the plant. Therefore, plants must balance the benefits of transpiration with the risk of water loss.
- 15. (a) Menarche — the first menstruation. Typical onset about 11–15 years (commonly 11–13 years but varies). (b) Napkin hygiene measures: use clean sanitary pads or tampons; change pads every 4–6 hours (or more often if needed); wash external genital area with mild soap and water and dry; wash hands before and after changing pads; wrap used pads in paper/plastic and dispose in bin or use napkin incinerator — do not flush; do not reuse disposable pads; store pads hygienically. (c) Yes. Rahini was correct — such advertisements raise awareness about menstrual hygiene and safe products.
- 16. Molar mass of CaCO3 = 40 + 12 + (3 x 16) = 100 g mol^-1. Percentage of Ca = (40/100) x 100 = 40%. Percentage of C = (12/100) x 100 = 12%. Percentage of O = (48/100) x 100 = 48%.
- 17. Grey matter is formed mainly by neuronal cell bodies (cytons), dendrites and unmyelinated nerve fibres (e.g., the cerebral cortex). Long VIII. Long Answer Questions 5 marks each <div
- 18. Collateral vascular bundle is one type of conjoint vascular bundle in which Xylem lies towards the centre and phloem lies towards the periphery. Eg : Dicot stem.
- 19. Cambium (vascular cambium) is absent in monocots, so secondary thickening does not occur.
- 20. The dark reaction, also known as the Calvin cycle, is a crucial part of photosynthesis where carbon dioxide from the atmosphere is converted into carbohydrates. This process occurs in the stroma of the chloroplasts. It utilizes the chemical energy stored in ATP and the reducing power of NADPH, both of which are generated during the preceding light-dependent reactions. Through a series of enzymatic steps, CO2 is 'fixed' and reduced to form sugars like glucose, which serve as food for the plant.
- 21. The light-dependent reaction of photosynthesis has specific inputs and outputs. The essential inputs are water, which is split to release electrons and protons, and solar energy, which is captured by photosynthetic pigments like chlorophyll. The primary end products of the light reaction are ATP and NADPH, which are energy-carrying molecules. Additionally, oxygen is released as a byproduct from the photolysis of water. These products are then utilized in the subsequent dark reaction to synthesize glucose.
- 22. Actions performed without our conscious control are called involuntary actions. Examples include heartbeat, breathing, digestion and reflex actions. <div
- 23. a. Fertilization b. Implantation (a) Fertilization - Fallopian tube (b) Implantation - Uterus.
- 24. The doctor would have explained that leeches possess a remarkable ability to make their bite painless initially. This is due to the secretion of an anaesthetic substance along with saliva when they attach to the skin, which numbs the area and prevents the host from feeling the bite immediately. Furthermore, the leech secretes hirudin, a powerful anticoagulant, which inhibits the clotting of blood. This ensures that the blood remains in a liquid state, allowing the leech to feed continuously and efficiently without interruption.
- 25. A - Exine B - Intine C - Generative cell D - Vegetative nucleus
- 26. The central part of the stem inner to endodermis is known as stele. It consists of pericycle, vascular bundle and pith. Vascular bundle : Vascular bundles are conjoint, collateral, endarch and open. They are arranged in the form of a ring around the pith.
- 27. A convex lens is capable of producing both real and virtual images, but it predominantly forms real images. When an object is placed at a distance greater than its focal length from the convex lens, the refracted rays converge to form a real, inverted image on the opposite side of the lens. A virtual, erect, and magnified image is formed only when the object is placed between the optical center and the principal focus of the lens.
- 28. Okazaki fragments are short DNA segments synthesized on the lagging strand during DNA replication; each fragment begins with an RNA primer and fragments are later joined by DNA ligase.
- 29. Ohm's law states that, at constant temperature, the current through a conductor is directly proportional to the potential difference across its ends. Thus V ∝ I, or V = IR, where R is the resistance of the conductor.
- 30. Cutting down of trees gives rise to ecological problems like floods, drought, soil erosion, loss of wildlife, extinction of species, imbalance of biogeochemical cycles, alteration of climatic conditions and desertification.
- 31. The teeth of a rabbit are described as heterodont because they exhibit variation in form and function, meaning different types of teeth are present. Specifically, rabbits possess incisors for gnawing, and premolars and molars for grinding. Notably, canine teeth are entirely absent in rabbits, which is a characteristic feature distinguishing them from many other mammals.
- 32. Linear expansion is also called longitudinal expansion. Its formula is Delta L = α L0 Delta T, where Delta L is change in length, L0 is original length, Delta T is temperature change, and α is the coefficient of linear expansion with unit K^-1.
- 33. True — Glucose is broken down into carbon dioxide, water and energy during aerobic respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (ATP).
- 34. Given: V = 0.3 m^3, Delta V = 0.25 m^3, Delta T = 50 K. Formula for cubical expansion: Delta V = γ V Delta T, so γ = Delta V / (V Delta T). Calculation: γ = 0.25 / (0.3 x 50) = 0.25 / 15 = 0.0166667 K^-1. Therefore, the coefficient of cubical expansion γ = 1.67 x 10^-2 K^-1.
- 35. Traffic signals are designed to be red primarily because of the physics of light scattering and the psychological impact of color. Red light possesses the longest wavelength within the visible spectrum. This long wavelength means it is scattered the least by atmospheric particles like dust, water droplets, and air molecules. Consequently, red light travels longer distances without significant dispersion, making it clearly visible from afar, even in conditions of fog or haze. Furthermore, red is a color that is easily distinguishable and has been conventionally adopted as a warning or stop signal across many cultures, allowing drivers to quickly and unambiguously recognize its meaning, thus enhancing road safety.
- 36. Transpiration : (i) Transpiration is the evaporation of water in plants through stomata in the leaves. (ii) Water evaporates from mesophyll cells of leaves through the open stomata, this lowers water concentration in mesophyll cells. (iii) As a result, more water is drawn into these cells from the xylem present in the veins through the process of osmosis. (iv) As water is lost from the leaves, pressure is created at the top to pull more water from the xylem to the mesophyll cells, this process is called transpiration pull. (v) This extends up to the roots causing the roots to absorb more water from the soil to ensure continuous flow of water from the roots to the leaves.
- 37. (i) Fossils are evidence for evolution. (ii) Fossils are the most important proof for evolution of life on earth over millions of years. They show that life on earth was once different from life found on earth today. (iii) By Studying fossils, help scientists to gather information about plants and animals which lived in the past ages. (iv) A plant fossil is any preserved part of a plant that has died long back. (v) Fossils may be a prehistoric impression that may be hundred to millions of years old. (vi) Majority of the plant fossils are disarticulated parts of plants, it is rare to find plants to be preserved as whole. Importance of fossils : (i) They throw light on phylogeny and evolution of plants. (ii) Fossil plants give a historical approach to plant kingdom. (iii) Thus even if fossils are not available as a whole, imprints or separated parts will also be able to give us lot of information about evaluation.
- 38. (i) The second gamete fuses with diploid secondary nucleus in the embryo sac of the ovule. (ii) This forms the triploid endosperm nucleus which develops into the endosperm tissue and gives nourishment to the developing embryo. (iii) When the ovule forms the seed after fertilization the endosperm serves to give nourishment to the embryo during germination until the first set of foliage leaves are formed by the seedling or baby plant.
- 39. The universal law of gravitation, formulated by Sir Isaac Newton, has profound applications in understanding the cosmos and celestial mechanics. Firstly, it is instrumental in determining the masses of celestial bodies like the Earth, the Moon, the Sun, and other planets by observing their gravitational effects on other objects. Secondly, it allows us to accurately calculate the acceleration due to gravity (g) at different points on Earth's surface and understand how it varies with altitude and depth. Thirdly, the law provides a fundamental explanation for the motion of planets around the Sun and the motion of natural satellites (like the Moon) and artificial satellites around planets, describing their elliptical orbits. Fourthly, it enables scientists to predict the paths and orbits of comets, asteroids, and other astronomical bodies, which is crucial for space exploration and hazard assessment. Fifthly, it explains the phenomenon of tides on Earth, which are primarily caused by the differential gravitational pull of the Moon and, to a lesser extent, the Sun on Earth's oceans. Finally, the universal law of gravitation is used in astrophysics to study binary star systems and to detect the presence of exoplanets by observing the subtle wobble or disturbance in the motion of nearby stars caused by the gravitational influence of an unseen orbiting planet.
- 40. Common modes of fossilization in plants (concise): - Permineralization (petrifaction): Minerals (silica, calcium carbonate) infiltrate and harden in cell spaces, preserving wood and bone structure. - Carbonization: Organic volatile elements are lost under pressure and heat, leaving a carbon film (common for leaves). - Impression/mold and cast: Organism leaves an impression (mold) in sediment; minerals may fill it to form a cast. - Compression: Plant parts are compressed in sediments leaving flattened fossils or impressions. - Replacement: Original material is dissolved and replaced by minerals molecule by molecule. - Preservation: Entire organisms/parts preserved in amber, peat, or ice (rapid exclusion of decay agents).
Brain Grain · braingrain.in
Science — Practice Paper · Set 3
Class: 10Samacheer KalviMax Marks: 86
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 15 × 1 = 15
Choose the correct answer. (Answer all questions.)
1.The eyes of the nocturnal birds like owl are having a large cornea and a large pupil. How does it help them?[1]
2.What precautions can be taken for preventing heart diseases ?[1]
3.“Wearing helmet and fastening the seat belt is highly recommended for safe journey” Justify your answer using Newton’s laws of motion.[1]
4.Cell phone towers should be placed far away from residential areas. Why?[1]
5.An organic compound ‘A’ is widely used as a preservative and has the molecular formula C2H4O2. This compound reacts with ethanol to form a sweet smelling compound ‘B’.[1]
6.‘A’ is a cylindrical structure that begins from the lower end of medulla and extend downwards. It is enclosed in bony cage ‘B’ and covered by membranes ‘C’. As many as ‘D’ pairs of nerves arise from the structure ‘A’. (i) What is A? (ii) Name (a) bony cage ‘B’ and (b) membranes ‘C’ (iii) How much is D?[1]
7.Our body contains a large number of cells ‘L’ which are the longest cells in the body. L has long and short branch called as ‘M’ and ‘N’ respectively. There is a gap ‘O’ between two ‘L’ cells, through which nerve impulse transfer by release of chemical substance ‘P’. (i) Name the cells L (ii) What are M and N? (iii) What is the gap O? (iv) Name the chemical substance P[1]
8.List any three activities based on 3R approach to conserve natural resources.[1]
9.Calculate the % relative abundance of B -10 and B -11, if its average atomic mass is 10.804 amu.[1]
10.How is the digestive system of rabbit suited for herbivorous mode of feeding?[1]
11.A piece of wire of resistance 10 ohm is drawn out so that its length is increased to three times its original length. Calculate the new resistance.[1]
12.a) Identify the bond between H and F in HF molecule.[1]
13.Explain the experiment of measuring the real and apparent expansion of a liquid with a neat diagram.[1]
14.Octopus, cockroach and frog all have eyes. Can we group these animals together to establish a common evolutionary origin. Justify your answer.[1]
15.While doing an experiment for the determination of focal length of a convex lens, Raja Suddenly dropped the lens. It got broken into two halves along the axis. If he continues his experiment with the same lens, (a) can he get the image? (b) Is there any change in the focal length?[1]
Part II — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
16.Mass can be measured using a physical balance[2]
17.How many pairs of testes are present in leech?[2]
18.Mention the function of endosperm.[2]
19.Its unit is kg (kilogram)[2]
20.Pith : Absent[2]
21.What is the minimum distance needed for an echo?[2]
22.Which hormone is secreted during emergency situation in man?[2]
23.The complete events of cardiac cycle last for 0.8 sec. What is the timing for each event?[2]
24.Define combination reaction. Give one example for an exothermic combination reaction.[2]
25.Which acts as a link between the nervous system and endocrine system?[2]
26.Distributing vessel : Collecting vessel[2]
27.Weight can be measured using a spring balance[2]
28.When is World Menstrual Hygiene Day observed?[2]
29.What is the importance of rainwater harvesting?[2]
30.The reactions of photosynthesis make up a biochemical pathway.[2]
31.It is used to treat myopia[2]
32.Define critical mass.[2]
33.A human hand, a front leg of a cat, a front flipper of a whale and a bat’s wing look dissimilar and adapted for different functions. What is the name given to these organs?[2]
Part III — Long Answer Questions 7 × 5 = 35
Answer in detail. (Answer all questions.)
34.Differentiate between systole and diastole. Explain the conduction of heart beat.[5]
35.Differentiate soaps and detergents.[5]
36.Organic farming is better than Green Revolution. Give reasons[5]
37.How many grams are there in the following?[5]
38.What are the sources of solid wastes? How are solid wastes managed?[5]
39.The electronic configuration of metal A is 2,8,18,1.[5]
40.What are the conditions which occur due to lack of ADH and insulin? How are the conditions different from one another?[5]
🔑 Show Answer Key — Set 3
- 1. The eyes of nocturnal birds like owls are adapted to see in low light conditions. A large cornea, which is the transparent outer layer of the eye, allows a greater amount of light to enter. Similarly, a large pupil, the opening in the center of the iris, can expand significantly to let in even more light. This increased light gathering capacity ensures that more light reaches the retina, where photoreceptor cells convert it into neural signals. Consequently, the bird can form a brighter and clearer image of its surroundings, enabling it to hunt and navigate effectively in the dim light of night.
- 2. Diet: reduce total calories if overweight; limit saturated fats and trans fats and dietary cholesterol; include moderate polyunsaturated and monounsaturated fats; reduce salt (sodium); eat more fruits, vegetables, whole grains and dietary fiber. Lifestyle: regular physical activity (daily exercise/walking), maintain healthy weight. Avoid smoking and excessive alcohol. Regular medical checkups to monitor blood pressure and blood cholesterol.
- 3. 1) State laws used: Newton's 1st law (inertia) and 2nd law (F = ma) plus impulse-momentum (Delta p = F_avg Delta t). 2) Describe the hazard: In a sudden stop or collision passenger's velocity v must change to zero (Delta v = -v); momentum change Delta p = mDelta v. 3) Use formula: average stopping force F_avg = mDelta v/Delta t. For fixed m and Delta v, larger Delta t -> smaller F_avg. 4) Apply to helmet: helmet cushions impact, increases Delta t and impact distance, so F_avg on skull decreases -> less injury. 5) Apply to seat belt: seat belt applies the unbalanced force to decelerate passenger, increases effective Delta t and spreads force across torso, preventing ejection and reducing localized injuries. 6) Units reminder: mass (kg), velocity (m/s), force (N = kg m/s2), impulse (N s). Example (optional): A 70 kg person at 20 m/s (72 km/h) stopped in 0.05 s -> F_avg approx. 70x20/0.05 = 28,000 N; if stopping time increases to 0.5 s with restraint/cushioning -> F_avg approx. 2,800 N, a tenfold reduction in average force.
- 4. Cell phone towers emit radio-frequency electromagnetic waves. To reduce continuous exposure and possible health concerns, they should be placed away from densely populated residential areas.
- 5. (i) Compound A is ethanoic acid (acetic acid), CH3COOH. (ii) It reacts with ethanol in the presence of concentrated H2SO4 to form the sweet-smelling ester ethyl ethanoate, B: CH3COOH + C2H5OH --conc. H2SO4-> CH3COOC2H5 + H2O (iii) The process is esterification.
- 6. (i) A – Spinal cord. (ii)(a) B – Vertebral column (b) C – Meninges. (iii) D – 31 pairs of spinal nerves.
- 7. (i) The cells referred to as L, which are the longest cells in the body and are fundamental to the nervous system, are neurons. (ii) M represents the axon, which is the long branch extending from the neuron's cell body, responsible for transmitting nerve impulses away from the cell. N represents the dendrites, which are the shorter, branching extensions that receive nerve impulses from other neurons and transmit them towards the cell body. (iii) The gap O between two neurons, across which nerve impulses are transmitted, is called a synapse. (iv) The chemical substance P released at the synapse to transfer the nerve impulse is a neurotransmitter, specifically acetylcholine in many cases.
- 8. (i) Reduce use of natural resources. E.g: coal. (ii) Reuse the waste whenever possible. Example water from kitchens can be used for growing plants. (iii) Recycle materials wherever possible. Example (a) Use of treated sewage water for gardening. (b) Bio wastes to be made into compost. ---
- 9. Let the percentage abundance of B-10 be x and B-11 be 100 - x. Average atomic mass = [10.01294x + 11.009305(100 - x)]/100 = 10.804. Solving, x = 20.636%. Therefore B-10 = 20.636% and B-11 = 79.364%.
- 10. The digestive system of a rabbit is highly adapted for its herbivorous diet, which primarily consists of fibrous plant material. Key adaptations include specialized dentition and a significantly enlarged caecum. Rabbits possess heterodont dentition, meaning they have different types of teeth suited for their diet, although they lack canine teeth. Their incisors are prominent for gnawing, followed by a gap called the diastema, which facilitates chewing and manipulation of food. The large, well-developed caecum is a crucial component where microbial fermentation occurs. This fermentation process, carried out by bacteria and other microorganisms, breaks down cellulose, a complex carbohydrate found in plant cell walls that rabbits cannot digest on their own. The caecum's structure and the presence of these symbiotic microbes allow rabbits to extract maximum nutrients from their fibrous food. Following caecal fermentation, rabbits practice coprophagy, re-ingesting soft fecal pellets (caecotrophes) to absorb the nutrients produced during fermentation, further enhancing nutrient assimilation.
- 11. Given initial R = 10 Ω. Let initial length = L and area = A. R = ρL/A = 10 Ω. New length = 3L. With constant volume, new area = A/3. R' = ρ(3L)/(A/3) = 9 (ρL/A) = 9R = 9 x 10 Ω = 90 Ω.
- 12. a) The bond between H and F in the HF molecule is a polar covalent bond. b) This identification is based on the significant difference in electronegativity between hydrogen and fluorine. Fluorine is highly electronegative, while hydrogen is less electronegative. This unequal sharing of electrons creates a partial positive charge on the hydrogen atom and a partial negative charge on the fluorine atom, resulting in a polar bond. c) Electronegativity generally increases from left to right across a period in the periodic table due to an increasing nuclear charge and a decrease in atomic radius. Conversely, electronegativity decreases as one moves down a group because the atomic radius increases and the outermost electrons are farther from the nucleus, experiencing less attraction.
- 13. Apparatus: small flask (or bulb) fitted with a narrow capillary tube, wooden or metal stand, scale/ruled glass behind the capillary (for marking heights), thermometer, burner. Procedure: 1. Fill the flask with the liquid up to a mark on the capillary and glass scale. Mark the initial level as L1 at room temperature and note the initial temperature T1. 2. Heat the flask gently. As the vessel (container) expands its internal volume increases and the liquid level in the capillary may fall slightly. When this fall is observed, mark this level as L2. 3. Continue heating so the liquid itself expands; the liquid level then rises and finally stabilises at L3 for a higher temperature T2. Observations and definitions: - Apparent expansion of the liquid = observed change relative to the original mark = L3 - L1. - Real (actual) expansion of the liquid = change of liquid level excluding container expansion = L3 - L2. - Therefore: Real = Apparent + (L1 - L2), where (L1 - L2) represents the change due to container expansion (drop in level). Relation between coefficients: - Let γ_liquid be the coefficient of cubical expansion of the liquid, γ_container that of the container, and γ_apparent the apparent coefficient observed. - γ_apparent = γ_liquid - γ_container. - Since the container is a solid, γ_container approx. 3α (α is the linear coefficient of the container). - Hence γ_liquid = γ_apparent + 3α. Formulas for a temperature change Delta T = (T2 - T1): - Real volume increase Delta V_real = V0 γ_liquid Delta T. - Apparent volume increase Delta V_apparent = V0 (γ_liquid - γ_container) Delta T. Notes for exam answers: - Label the neat diagram: flask/bulb, capillary tube, scale, L1, L2, L3, thermometer, burner. - Give units: coefficients in °C^-1 (per degree Celsius) and volume in m3 (or cm3) when needed. - State conclusion: real expansion of a liquid is greater than its apparent expansion because the container also expands.
- 14. No. They cannot be grouped solely on presence of eyes. Correct classification: octopus — phylum Mollusca (Cephalopoda); cockroach — phylum Arthropoda (Insecta); frog — phylum Chordata (Amphibia).
- 15. (a) Yes, he can still get the image using one half of the broken convex lens. (b) There is no change in the focal length because the curvature of the lens surfaces does not change. However, the intensity or brightness of the image will be reduced because less light passes through the broken lens.
- 16. True. Mass can be accurately measured using a physical balance, also known as a beam balance. This instrument works on the principle of moments and compares the unknown mass placed on one pan with known standard masses placed on the other pan. When the beam is balanced, the unknown mass is equal to the sum of the standard masses used. The SI unit for mass is the kilogram (kg), and physical balances are a common and reliable method for determining this fundamental property of matter.
- 17. 11 pairs of testes are present in leech.
- 18. The endosperm is a nutritive tissue formed within the seeds of most flowering plants after fertilization. Its primary function is to provide nourishment to the developing embryo during its growth, both before germination and in the early stages after germination begins. The endosperm is rich in stored food materials such as starch, oils, and proteins, which are essential for the embryo's development and eventual sprouting into a new plant. In some plants, like beans, the endosperm is completely absorbed by the cotyledons before the seed matures, while in others, like castor oil seeds, the endosperm remains a significant source of food for the seedling.
- 19. The quantity described is mass. Its SI unit is the kilogram (kg), which is the base unit of mass in the International System of Units. The kilogram is a measure of the amount of matter in an object and is a fundamental property that remains constant regardless of the object's location or the gravitational field it is in. While other units like grams (g) or milligrams (mg) are used for smaller quantities, the kilogram is the standard unit for scientific and everyday measurements.
- 20. Pith: Absent — characteristic of dicot root (central region is occupied by xylem; pith is usually absent).
- 21. For a distinct echo, the reflected sound should reach the ear after at least 0.1 s. Since sound travels to the obstacle and back, 2d/v >= 0.1. Taking v about 344 m s-1, d >= 17.2 m. So the minimum distance is about 17 m.
- 22. Adrenalin.
- 23. Events of cardiac cycle - Total duration 0.8 sec. a) Atrial systole (Contraction of auricles) - 0.1 sec b) Ventricular systole (Contraction of ventricles) - 0.3 sec c) Ventricular diastole (Relaxation of ventricles) - 0.4 sec Total duration of cardiac cycle - 0.8 sec
- 24. A combination reaction is a reaction in which two or more reactants combine to form a single product. It is also called a synthesis reaction or composition reaction. Example: On burning magnesium in air, it combines with oxygen to form magnesium oxide: 2Mg(s) + O2(g) -> 2MgO(s)
- 25. Hypothalamus of the fore brain acts as a link between nervous and endocrine system.
- 26. A distributing vessel is a blood vessel that carries blood away from the heart to various parts of the body, which is characteristic of an artery. A collecting vessel is a blood vessel that gathers blood from different parts of the body and returns it to the heart, which is the function of a vein. Therefore, the distributing vessel is an artery, and the collecting vessel is a vein.
- 27. True. Weight can be measured using a spring balance because a spring balance measures force. If the reading is in newtons, it directly gives the weight. Weight is given by W = mg.
- 28. World Menstrual Hygiene Day is observed annually on May 28. This day is dedicated to raising awareness about the importance of good menstrual hygiene management (MHM) and addressing the challenges faced by women and girls worldwide regarding menstruation. The date May 28 was chosen because it represents the 5th day of the 5th month, symbolizing the 5 days of menstruation and the 28-day average menstrual cycle. The day aims to promote the use of safe and hygienic menstrual products, provide access to sanitation facilities, and break the stigma and taboos associated with menstruation.
- 29. Rainwater harvesting collects and stores rainwater (e.g., from roofs) to recharge groundwater and store water for use. It helps conserve water, raise groundwater levels, reduce surface runoff and floods, decrease soil erosion, and provide a cleaner supplementary water source.
- 30. Photosynthesis involves two main sets of reactions that form a biochemical pathway. The light-dependent reactions occur in the grana of the chloroplasts, where water (H2O) is split and light energy is captured to produce oxygen (O2) as a byproduct, along with the energy-rich molecules ATP and NADPH. Subsequently, the dark reaction, or Calvin cycle, takes place in the stroma of the chloroplasts. This cycle uses the CO2 from the atmosphere along with the ATP and NADPH generated in the light reactions. Its primary products are triose phosphates, which are then used to synthesize glucose and other carbohydrates, and the regeneration of RuBP (ribulose-1,5-bisphosphate), a key molecule required to initiate the cycle again.
- 31. The vision defect known as myopia, or short-sightedness, is effectively treated using a concave lens. Myopia occurs when the eye focuses distant objects in front of the retina, leading to blurred vision for faraway objects. A concave lens, being a diverging lens, reduces the converging power of the eye's optical system. It causes the incoming parallel rays from distant objects to diverge slightly before entering the eye, ensuring that the final image is formed precisely on the retina, thus correcting the defect.
- 32. Critical mass is the minimum amount of fissile material, such as uranium-235 or plutonium-239, required to achieve and sustain a nuclear chain reaction. This mass is not fixed but depends on various factors including the shape, density, purity of the fissile material, and the presence of a neutron reflector. Below the critical mass, a chain reaction will not be sustained as too many neutrons escape.
- 33. Homologous organs.
- 34. Systole is the phase of the cardiac cycle when the heart muscle contracts, pumping blood out of the chambers. This can refer to either atrial systole, where the atria contract, or ventricular systole, where the ventricles contract. Diastole, on the other hand, is the phase when the heart muscle relaxes, allowing the chambers to fill with blood. The conduction of a heartbeat begins in the sinoatrial (SA) node, located in the wall of the right atrium, which generates an electrical impulse. This impulse spreads across the atria, causing them to contract (atrial systole). The impulse then reaches the atrioventricular (AV) node, where there is a brief delay to ensure the ventricles are adequately filled with blood. From the AV node, the impulse travels down the Bundle of His, which then divides into the right and left bundle branches. These branches carry the impulse to the Purkinje fibres, which distribute it throughout the ventricular myocardium, triggering ventricular contraction (ventricular systole).
- 35. Soap i. It is a sodium or potassium salt of long-chain fatty acids. ii. The ionic part of a soap is R-COO- Na+. iii. It is prepared from animal fats or vegetable oils. iv. It works well in soft water, but its effectiveness is reduced in hard water. v. It forms scum with Ca2+ and Mg2+ ions in hard water. vi. Soaps are biodegradable. Detergent i. It is generally a sodium salt of sulphonic acids. ii. The ionic part in a detergent is R-SO3- Na+. iii. It is prepared from hydrocarbons obtained from petroleum/crude oil. iv. It is effective even in hard water. v. It does not form scum in hard water. vi. It has good foaming capacity; many conventional detergents are non-biodegradable.
- 36. Green revolution is the process of increasing food production through high yielding crop varieties and modern agricultural techniques in under developed and developing nations. This has increased production and helped India tide over food crisis. But this requires high yielding varieties of crops got by artificial methods like breeding, use of fertilizers and pesticides. Some disadvantages have been listed below : (i) This promotes monoculture of certain desired plant varieties. (ii) Use of fertilizers I pesticides in excess alters the chemical composition of the soil. (iii) All farmers cannot afford the cost. (iv) Environmentalists felt that because of green revolution the soil was affected and certain traditional crops varieties have been neglected. Organic Farming : (i) In contrast organic farming avoids utilization of synthetic fertilizers, chemical pesticides and makes use of green manures, compost and biological pest control which do not harm the environment. (ii) Further growing different plant species will lead to efficient use of nutrients and cause fewer outbreaks of disease. (iii) Organic farming techniques like Inter cropping, use of companion plants will also increase biodiversity. Thus organic farming is stable, sustainable and beneficial for the future generations.
- 37. (i) 2 moles of H2: molar mass = 2 g mol^-1, mass = 2 x 2 = 4 g. (ii) 3 moles of Cl2: molar mass = 70.9 g mol^-1, mass = 3 x 70.9 = 212.7 g. (iii) 5 moles of S8: molar mass = 32 x 8 = 256 g mol^-1, mass = 5 x 256 = 1280 g. (iv) 4 moles of P4: molar mass = 31 x 4 = 124 g mol^-1, mass = 4 x 124 = 496 g.
- 38. Sources of solid waste : (i) Solid wastes mainly include municipal wastes, hospital wastes, industrial wastes and e-wastes etc. (ii) The solid wastes are dumped in the soil which results in landscape pollution. (iii) Solid - waste management involves the collection, treatment and proper disposing of solid material that is discarded from the household and industrial activities. Methods of solid wastes disposal: (i) Segregation : It is the separation of different type of waste materials like biodegradable and non biodegradable wastes. (ii) Sanitary land fill : Solid wastes are dumped into low lying areas. The layers are compacted by trucks to allow settlement. The waste materials get stabilised in 2-12 months. The organic matter undergoes decomposition. (iii) Incineration: It is the burning of non- biodegradable solid wastes (medical wastes) in properly constructed furnace at high temperature. (iv) Composting : Biodegradable matter of solid wastes is digested by microbial action or earthworms and converted into humus. Recycling of wastes : (i) Papers from old books, magazines and news papers are recycled to produce papers in papermills. (ii) Agricultural wastes like coconut shells, jute, cotton stalk, bagasse of sugarcane can be used to make paper and hard board. Paddy husk can be used as livestock fodder. (iii) Cowdung and other organic wastes can be used in gobar gas plant to provide biogas and manure for fields. 3R Approach : The 3R approach such as, Reduce, Reuse and Recycle may be followed for effective waste management.
- 39. The metal A is copper (Cu). When copper is exposed to air and moisture, it forms a green layer of basic copper carbonate: 2Cu + O2 + CO2 + H2O -> CuCO3.Cu(OH)2 So, B is basic copper carbonate. With concentrated sulphuric acid, copper forms copper sulphate, sulphur dioxide and water: Cu + 2H2SO4 -> CuSO4 + SO2 + 2H2O So, C is copper sulphate (CuSO4) and D is sulphur dioxide (SO2).
- 40. (a) ADH - Anti diuretic hormone produced by posterior lobe of pituitary gland and is also known as Vasopressin. Deficiency of ADH reduces reabsorption of water and causes an increase in urine output (polyuria). This deficiency disorder is called Diabetes insipidus. Insulin - Hormone produced by beta cells of Islets of Langerhans. The deficiency of insulin causes Diabetes mellitus. It is charactersied by (i) Increase in blood sugar level (Hyperglycemia). (ii) Excretion of excess glucose in the urine (Glycosuria). (iii) Frequent urination (Polyuria). (iv) Increased thirst (Polydipsia). (v) Increase in appetite (Polyphagia). (b) Diabetes insipidus results in increase of urine output. In the case of diabetes mellitus there is frequent urination (polyuria) and excess of glucose is also secreted along with urine. (Glycosuria). IX Higher Order Thinking Skills (HOTS)