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Science Answers Answers to Science Questions **1. Which of the following groups contain only biodegradable items?** (a) Grass, flowers and leather (b) Grass, wood and plastic (c) Fruit-peels, cake and lime-juice (d) Cake, wood and grass Answer: (c) Fruit-peels, cake and lime-juice **2. Which of the following constitute a food-chain?** (a) Grass, wheat and mango (b) Grass, goat and human (c) Goat, cow and elephant (d) Grass, fish and goat Answer: (b) Grass, goat and human **3. Which of the following are environment-friendly practices?** (a) Carrying cloth-bags to put purchases in while shopping (b) Switching off unnecessary lights and fans (c) Walking to school instead of getting your mother to drop you on her scooter (d) All of the above Answer: (d) All of the above **4. What will happen if we kill all the organisms in one trophic level?** Answer: Killing all organisms in one trophic level will disrupt the food cha...

Science Answers Answers to Science Questions 1. Which of the following correctly describes the magnetic field near a long straight wire? (a) The field consists of straight lines perpendicular to the wire. (b) The field consists of straight lines parallel to the wire. (c) The field consists of radial lines originating from the wire. (d) The field consists of concentric circles centred on the wire. Answer: (d) The field consists of concentric circles centred on the wire. 2. At the time of short circuit, the current in the circuit (a) reduces substantially. (b) does not change. (c) increases heavily. (d) vary continuously. Answer: (c) increases heavily. State whether the following statements are true or false. (a) The field at the centre of a long circular coil carrying current will be parallel straight lines. Answer: True (b) A wire with a green insulation is usually the live wire of an electric supply. Answer: False List ...

Science Answers Answers to Science Questions 1. A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R’, then the ratio R/R’ is – (d) 25  (c) 5  (b) 1/5  (a) 1/25 Answer: (d) 25 2. Which of the following terms does not represent electrical power in a circuit? (d) V^2/R  (c) VI  (b) IR^2  (a) PR Answer: (b) IR^2 3. An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be – (d) 25 W  (c) 50 W  (b) 75 W  (a) 100 W Answer: (c) 50 W 4. Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be– (d) 4:1  (c) 1:4  (b) 2:1  (a) 1:2 Answer: (c) 1:4 5. How is a voltmeter connected in the circuit to measure t...

Science Answers Answers to Science Questions 1. The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to (a) presbyopia. (b) accommodation. (c) near-sightedness. (d) far-sightedness. Answer: (b) accommodation. 2. The human eye forms the image of an object at its (a) cornea. (b) iris. (c) pupil. (d) retina. Answer: (d) retina. 3. The least distance of distinct vision for a young adult with normal vision is about (a) 25 m. (b) 2.5 cm. (c) 25 cm. (d) 2.5 m. Answer: (c) 25 cm. 4. The change in focal length of an eye lens is caused by the action of the (a) pupil. (b) retina. (c) ciliary muscles. (d) iris. Answer: (c) ciliary muscles. 5. A person needs a lens of power –5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near ...

Light – Reflection and Refraction Question 1 1. Which one of the following materials cannot be used to make a lens? (a) Water (b) Glass (c) Plastic (d) Clay Answer 1 Answer: (d) Clay Explanation: A lens is a transparent medium that refracts light. Clay is an opaque material that does not allow light to pass through it, so it cannot be used to make a lens. Question 2 2. The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object? (a) Between the principal focus and the centre of curvature (b) At the centre of curvature (c) Beyond the centre of curvature (d) Between the pole of the mirror and its principal focus. Answer 2 Answer: (d) Between the pole of the mirror and its principal focus. Explanation: When an object is placed between the pole and principal focus of a concave mirror, the image formed is virtual, erect, and larger than the object. Question 3 3. Where should an obje...

Genetics Q&A for Class 10 1. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as (a) TTWW (b) TTww (c) TtWW (d) TtWw Answer: (c) TtWW Explanation: Violet (W) is dominant over white (w), and all F 1 plants bear violet flowers, so the tall parent must be homozygous WW. Tall (T) is dominant over short (t), and half the progeny are short, so the tall parent must be heterozygous Tt. 2. A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not? Answer: We cannot conclude whether light-coloured eyes are dominant or recessive solely from this observati...

Reproduction Q&A 1. Asexual reproduction takes place through budding in (a) Amoeba. (b) Yeast. (c) Plasmodium. (d) Leishmania. Answer: (b) Yeast Step-by-step reasoning: Budding is a type of asexual reproduction where a new organism grows out of the body of the parent. In yeast, a small protuberance (bud) forms on the parent cell, its nucleus divides, and one nucleus migrates into the bud. The bud enlarges and eventually detaches as an independent yeast cell. Other organisms listed reproduce by binary fission (Amoeba), sporozoite formation (Plasmodium), or other modes (Leishmania). 2. Which of the following is not a part of the female reproductive system in human beings? (a) Ovary (b) Uterus (c) Vas deferens (d) Fallopian tube Answer: (c) Vas deferens Step-by-step reasoning: Ovary, uterus, and fallopian tube are intrinsic to the female reproductive tract. Vas defe...

Life Processes Questions and Answers 1. The kidneys in human beings are a part of the system for (a) nutrition. (b) respiration. (c) excretion. (d) transportation. Answer: (c) excretion. 2. The xylem in plants are responsible for (a) transport of water. (b) transport of food. (c) transport of amino acids. (d) transport of oxygen. Answer: (a) transport of water. 3. The autotrophic mode of nutrition requires (a) carbon dioxide and water. (b) chlorophyll. (c) sunlight. (d) all of the above. Answer: (d) all of the above. 4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in (a) cytoplasm. (b) mitochondria. (c) chloroplast. (d) nucleus. Answer: (b) mitochondria. 5. How are fats digested in our bodies? Where does this process take place? Fats are emulsified by bile salts in the small intestine, breaking large globu...

Science Answers Answers to Science Questions 1. Which of the following is a plant hormone? (a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin. Answer: (d) Cytokinin. 2. The gap between two neurons is called a (a) dendrite. (b) synapse. (c) axon. (d) impulse. Answer: (b) synapse. 3. The brain is responsible for (a) thinking. (b) regulating the heart beat. (c) balancing the body. (d) all of the above. Answer: (d) all of the above. 4. What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise? Answer: Receptors detect changes in the environment and send signals to the brain. If they don’t work properly, problems like inability to feel pain, temperature, or touch, and difficulty in responding to stimuli may arise. 5. Draw the structure of a neuron and explain its function. Answer: [Imagine a neuron with a cell body, dendrites, axon...

Science Answers Answers to Science Questions 1. Ethane, with the molecular formula C₂H₆, has (a) 6 covalent bonds. (b) 7 covalent bonds. (c) 8 covalent bonds. (d) 9 covalent bonds. Answer: (a) 6 covalent bonds. 2. Butanone is a four-carbon compound with the functional group (a) carboxyl acid. (b) aldehyde. (c) ketone. (d) alcohol. Answer: (c) ketone. 3. While cooking, if the bottom of the vessel is getting blackened on the outside, it means that (a) the food is not cooked completely. (b) the fuel is not burning completely. (c) the fuel is wet. (d) the fuel is burning completely. Answer: (b) the fuel is not burning completely. 4. Explain the nature of the covalent bond using the bond formation in CH₄. Answer: In CH₄ (methane), a covalent bond forms when carbon shares its four valence electrons with four hydrogen atoms. Each carbon-hydrogen bond is created by the sharing of electron pairs, resulting in a stable molec...

Science Answers Answers to Science Questions 1. Which of the following pairs will give displacement reactions? (a) NaCl solution and copper metal (b) MgCl₂ solution and aluminium metal (c) FeSO₄ solution and silver metal (d) AgNO₃ solution and copper metal Answer: (d) AgNO₃ solution and copper metal 2. Which of the following methods is suitable for preventing an iron frying pan from rusting? (a) Applying grease (b) Applying paint (c) Applying a coating of zinc (d) All of the above. Answer: (d) All of the above. 3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be (a) calcium (b) carbon (c) silicon (d) iron Answer: (a) calcium 4. Food cans are coated with tin and not with zinc because (a) zinc is costlier than tin. (b) zinc has a higher melting point than tin. (c) zinc is more reactive than tin. (d) zinc is less re...

Science Answers Answers to Science Questions 1. A solution turns red litmus blue. Is pH likely to be (a) 1 (b) 4 (c) 5 (d) 10 Answer: (d) 10 2. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains Answer: HCl 3. 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be (a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL Answer: (d) 16 mL 4. Which one of the following types of medicines is used for treating indigestion? (a) Antibiotic (b) Analgesic (c) Antacid (d) Antiseptic Answer: (c) Antacid 5. Write word equations and then balanced equations for the reaction taking place when- (a) dilute sulphuric acid reacts with zinc granules. Word equation: Sulphuric acid + Zinc → Zinc sulphate + Hydrogen Balanced equatio...

Class 10 Chemical Reactions and Equations - Full Questions and Answers Class 10 Chemical Reactions and Equations - Full Questions and Answers 1. Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) → 2Pb(s) + CO₂(g) (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced. (i) (a) and (b) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all Answer: (i) (a) and (b) are incorrect. 2. Fe₂O₃ + 2Al → Al₂O₃ + 2Fe The above reaction is an example of a (a) combination reaction. (b) double displacement reaction. (c) decomposition reaction. (d) displacement reaction. Answer: (d) displacement reaction. 3. What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydr...

Class 10 Chemical Reactions and Equations - Notes Class 10 Chemical Reactions and Equations - Notes 1. Which of the statements about the reaction below are incorrect? Answer: (i) (a) and (b) are incorrect. 2. Fe 2 O 3 + 2Al → Al 2 O 3 + 2Fe Answer: (d) displacement reaction. 3. What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. Answer: (a) Hydrogen gas and iron chloride are produced. 4. What is a balanced chemical equation? Why should chemical equations be balanced? Answer: A balanced chemical equation has the same number of atoms of each element on both sides. Equations should be balanced to follow the law of conservation of mass. 5. Translate the following statements into chemical equations and then balance them. (a) N 2 + 3H 2 → 2NH 3 (b) 2H 2 S + 3O 2 → 2H 2 O + 2SO 2 (c) 3BaCl 2 + Al 2 (SO 4 ) 3 → 2AlCl 3 + 3BaSO 4 (d) 2K + 2H 2 O → 2KOH + H 2 ...

Crop Production Exercises Answers (Complete) Crop Production Exercises Answers 1. Explain any one method of crop production which ensures high yield. Using high-yielding variety (HYV) seeds is a method of crop production that ensures high yield. These seeds are specially developed to give more production, resist pests, and grow well in different conditions, helping farmers get more crops from the same land. 2. Why are manure and fertilizers used in fields? • Manure and fertilizers provide essential nutrients like nitrogen, phosphorus, and potassium to the soil. • They increase soil fertility, which helps plants grow healthier and faster. • They improve the structure and water-holding capacity of the soil. • They help in getting higher yield by providing nutrients to crops. 3. What are the advantages of inter-cropping and crop rotation? Aspect Inter-cropping Crop Rotation Definition Growing two or more crops together on the same field in a specific pattern. Growing ...

Sound Exercises Answers Sound Exercises Answers 1. What is sound and how is it produced? Sound is a form of energy that produces the sensation of hearing. It is produced by vibrating objects. When an object vibrates, it makes the particles of the medium around it vibrate, and these vibrations reach our ear, producing sound. 2. Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound. When a vibrating object moves forward, it pushes the air in front, creating a compression (region of high pressure). When it moves backward, it creates a rarefaction (region of low pressure). Source of Sound --> Pushes Air --> Compression Moves Back --> Rarefaction These compressions and rarefactions travel in the air as sound waves . 3. Why is sound wave called a longitudinal wave? Sound waves are called longitudinal waves because the particles of the medium move back and forth in t...

Exercises Exercises Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term 'work'. Suma is swimming in a pond. Answer: Work is done as she applies force and moves in the direction of force. A donkey is carrying a load on its back. Answer: No work is done in the scientific sense since the force (upward) and displacement (forward) are perpendicular. A wind-mill is lifting water from a well. Answer: Work is done as the force by the windmill lifts water upward, displacing it in the direction of force. A green plant is carrying out photosynthesis. Answer: No work is done in the physics sense as there is no displacement due to applied force. An engine is pulling a train. Answer: Work is done...

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Gravitation Exercises with Answers - Class 9 Exercises with Answers How does the force of gravitation between two objects change when the distance between them is reduced to half? Answer: The force becomes four times because gravitational force is inversely proportional to the square of the distance between the objects. Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object? Answer: Because the acceleration due to gravity is the same for all objects irrespective of their masses, so both fall at the same rate. What is the magnitude of the gravitational force between the earth and a 1 kg object on its surface? (Mass of the earth is 6 x 10 24 kg and radius of the earth is 6.4 x 10 6 m.) Answer: Using F = GMm/R 2 , F = (6.67 x 10 -11 x 6 x 10 24 x 1) / (6...

Force and Laws of Motion - Class 9 Exercises Force and Laws of Motion - Class 9 Exercises 1. An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the object. Answer: Yes, if the object is moving with constant velocity in a straight line without any unbalanced force acting on it, it will continue moving with that velocity as per Newton's First Law. 2. When a carpet is beaten with a stick, dust comes out of it. Explain. Answer: The carpet moves when beaten, but the dust tends to remain at rest due to inertia and separates out from the carpet. 3. Why is it advised to tie any luggage kept on the roof of a bus with a rope? Answer: To prevent the luggage from moving forward and falling off due to inertia if the bus stops suddenly. 4. A batsman hits a cricket ball which then...