Previous CBSE board exam questions — Science (Class 10)

Previous-year CBSE board exam questions in Science, with model answers. 1000 question(s), grouped by chapter and skill.

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Chemistry · Chapter 1: Chemical Reactions and Equations (92)

• The volume ratio of hydrogen and oxygen gases liberated during electrolysis of water is
• C₆H₁₂O₆(aq) + 6O₂(g) → 6CO₂(g) + 6H₂O(l). The above reaction is an example of
• Answer the following : A compound 'A' is used in soda-lime fire-extinguisher and decomposes on heating to for…
• Account for the following : White silver chloride turns grey when exposed to sunlight.
• Account for the following : Lead (II) nitrate on heating releases brown fumes.
• Account for the following : Bags of oil and fat containing food items are flushed with nitrogen gas.
• Attempt either option (A) or (B). Option (A):
• (i) AgNO₃ + NaCl → NaNO₃ + AgCl (ii) K₂SO₄ + BaCl₂ → BaSO₄ + 2KCl Which of the following options clearly desc…
• The gases evolved on heating lead (II) nitrate crystals are :
• Answer the following : Name the substance oxidised and reduced in the following reaction : ZnO + C → Zn + CO
• Answer the following : Balance the following chemical reaction : Pb(NO₃)₂ + KI → PbI₂ + KNO₃
• Answer the following : Give one example each of electrolytic decomposition and decomposition by sunlight.
• Study the following table and select the correct option :
• Assertion (A) : Reaction of quick lime with water is an exothermic reaction. Reason (R) : A large amount of h…
• What happens when (i) lead (II) nitrate is heated ? (ii) iron (II) sulphate is heated ? (iii) silver chloride…
• Which of the following are combination reactions ? (i) 2KClO₃ ⎯⎯→ 2KCl + 3O₂ (ii) MgO + H₂O ⎯⎯→ Mg(OH)₂ (iii)…
• A metal carbonate reacts with a solution X which forms a salt, water and a gas Y. What are X and Y ?
• When ferrous sulphate crystals are heated in a test tube, we observe that :
• A student notices that her silver jewellery turned dull and had a grey-black coating over it after wearing fo…
• Seema took a small amount of copper powder in a china dish and heated it. What changes will she observe on he…
• Observe the figure given below and identify the incorrect step for the activity set-up :
• Which of the following is an example of a displacement reaction ?
• To a small amount of copper oxide in a beaker, when we add dilute hydrochloric acid slowly with stirring, the…
• In the following equation x KI + H₂O₂ ⎯→ I₂ + y KOH x and y respectively are :
• 2 g of green coloured crystals of ferrous sulphate are heated in a dry boiling tube. Name the type of chemica…
• Electrolysis of water is a decomposition reaction. The mass ratio (MH : MO) of hydrogen and oxygen gases libe…
• The formation of magnesium oxide is correctly shown in option :
• Assertion (A) : Decomposition reactions are generally endothermic reactions. Reason (R) : Decomposition of or…
• A student performs the following experiment in his school laboratory. List two observations to justify that i…
• With the help of an activity, explain the conditions under which iron articles get rusted.
• The correct balanced chemical equation showing exothermic reaction in which natural gas burns in air is :
• Answer the following: In common practice silver is recovered from silver nitrate solution by the use of coppe…
• Answer the following:
• Consider the following chemical equation : p Al + q H₂O ⟶ r Al₂O₃ + s H₂ To balance this chemical equation, t…
• List the possible sources of energy required in decomposition reactions. Illustrate any one with a suitable e…
• What is observed when hydrated ferrous sulphate crystals are heated in a dry boiling tube ? Give balanced che…
• Zn + 2CH₃COOH → (CH₃COO)₂Zn + H₂ The above reaction is a :
• What is a chemical reaction ? Describe one activity each to show that a chemical change has occurred in which…
• (i) Define a decomposition reaction. How can we say that (I) electrolysis of water, and (II) blackening of si…
• To balance the following chemical equation, the values of the coefficients x, y and z must be respectively :…
• Which of the following is a redox reaction, but not a combination reaction ?
• Answer either (a) or (b):
• Study the experimental set-up shown in the diagram and write chemical equation for the chemical reaction invo…
• Which of the following is an example of endothermic process ?
• In order to balance the following chemical equation, the values of the coefficients x and y respectively are…
• Answer the following:
• (a) What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name th…
• Silver chloride kept in a china dish turns grey in sunlight.
• When aqueous solutions of potassium iodide and lead nitrate are mixed, an insoluble substance separates out.…
• Assertion (A) : Reaction of Quicklime with water is an exothermic reaction. Reason (R) : Quicklime reacts vig…
• (A) A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it…
• Answer the following:
• The balanced chemical equation showing reaction between quicklime and water is :
• Study the following chemical reaction : 2 Na (s) + 2 H₂O (l) → 2 NaOH (aq) + H₂ (g) The reducing agent in thi…
• Define a double displacement reaction. Write the chemical equation of a double displacement reaction which is…
• Answer the following : Why do copper sulphate crystals turn white on heating ?
• Answer the following : Identify the type of chemical reaction that takes place when a solution of copper sulp…
• In which one of the following situations a chemical reaction does not occur?
• Define oxidation. Identify and name the substance oxidised in the following reaction : CuO + H₂ → Cu + H₂O
• Why do we balance a chemical equation? Name and state the law that suggests the balancing of a chemical equat…
• Define a precipitation reaction. Give its example and also express the reaction that occurs in the form of a…
• The main observations while performing the experiment of burning magnesium ribbon in air are : (i) Magnesium…
• The values of a, b, c and d in the following balanced chemical equation are respectively : a Pb(NO₃)₂ --heat-…
• Assertion (A) : Silver chloride turns grey in sunlight. Reason (R) : Decomposition of silver chloride into si…
• A crystalline substance of green colour 'X' emits gases of characteristic odour when heated over a flame. It…
• In the following experimental setup of electrolysis of water, if P and Q are the gases collected in the test…
• Select from the following a statement which is not true about burning of magnesium ribbon in air :
• The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is
• A light green coloured solution of sulphate salt of metal 'P' is taken in a beaker, a rod of another metal 'Q…
• Write balanced chemical equation for the reactions that occur when (a) steam is passed over red hot iron. (b)…
• When 2 mL of sodium hydroxide solution is added to few pieces of granulated zinc in a test tube and then warm…
• Select from the following a decomposition reaction in which source of energy for decomposition is light :
• MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂ The reaction given above is a redox reaction because in this case :
• Name the type of chemical reaction in which calcium oxide reacts with water. Justify your answer by giving ba…
• Write one chemical equation each for the chemical reaction in which the following have taken place : Mention…
• Solid Calcium oxide reacts vigorously with water to form Calcium hydroxide accompanied by the liberation of h…
• Select from the following a process in which a combination reaction is involved :
• Identify the correct statement about the following reaction : 2H₂S + SO₂ ⟶ 2H₂O + S
• "No precipitation reaction can occur without exchange of ions between the two reactants." Justify this statem…
• Giving one example of each, differentiate between a displacement reaction and a double displacement reaction.
• Identify the product 'X' obtained in the following chemical reaction : CaCO₃ ⎯Δ→ 'X' + CO₂
• Consider the following Chemical equation : a Al₂O₃ + b HCl ⟶ c AlCl₃ + d H₂O. In order to balance this chemic…
• Which one of the following reactions is different from the remaining three ?
• When magnesium ribbon is burnt in air, an ash of white colour is produced. Write chemical equation for the re…
• In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the…
• The emission of brown fumes in the given experimental set-up is due to
• MnO₂ + x HCl → MnCl₂ + y H₂O + z Cl₂ In order to balance the above chemical equation, the values of x, y and…
• Assertion (A) : The colour of aqueous solution of copper sulphate turns colourless when a piece of lead is ad…
• Write balanced chemical equation for the reaction that occurs when :
• Answer the following:
• Select the appropriate state symbols of the products given as X and Y in the following chemical equation by c…
• State whether the given chemical reaction is a redox reaction or not. Justify your answer. MnO₂ + 4HCl ⟶ MnCl…

Chemistry · Chapter 2: Acids, Bases and Salts (86)

• An aqueous solution turns red litmus blue. Excess addition of which of the following solution would reverse t…
• How will you protect yourself from the heat generated while diluting a concentrated acid ?
• Answer the following : A compound 'A' is used in soda-lime fire-extinguisher and decomposes on heating to for…
• Answer the following : Write chemical formula of Plaster of Paris. At what temperature gypsum is heated to ob…
• Attempt either option (A) or (B). Option (B):
• The pH plays an important role in our daily life. Strength of acids and bases depends on the number of H⁺ ion…
• Attempt either option (A) or (B). Option (A):
• Attempt either option (A) or (B). Option (B):
• Which one of the following can be used as an acid-base indicator by a visually impaired (blind) student ?
• The natural sources of oxalic acid, lactic acid and methanoic acid respectively are :
• Answer the following : Categorise the following based on their nature : ZnO, Na₂O, CO₂
• Explain chlor-alkali process with chemical equation. Name the products formed at anode and cathode.
• Write the preparation of following compounds with balanced chemical equation : (i) Baking soda (ii) Bleaching…
• Four solutions, namely fructose, ethanol, hydrochloric acid and sodium hydroxide filled in four separate beak…
• Which gas is evolved when magnesium metal reacts with very dilute HNO₃ ?
• Define the following terms : (i) Olfactory indicator (ii) Water of crystallization Olfactory indicator
• Define the following terms : (i) Olfactory indicator (ii) Water of crystallization Water of crystallization
• Answer the following:
• Answer the following:
• The pH of the gastric juices released during digestion is :
• Baking powder is a mixture of :
• Read the following passage and answer the questions that follow :
• Give reasons :
• Write the preparation of the following compounds with balanced chemical equation :
• The following table shows the pH values of four solutions A, B, C and D on a pH scale : 1 2 3 4 5 6 7 8 9 10…
• Consider the following reactions : (i) Dilute hydrochloric acid reacts with sodium hydroxide. (ii) Magnesium…
• Read the passage carefully and answer the questions that follow.
• The warning sign shown in the given figure must invariably be displayed/pasted on the containers which contai…
• The body of human beings works within the pH range of :
• Read the case carefully and answer the questions that follow.
• Which of the given option represents a family of salts ?
• Answer the following :
• Common salt is an important raw material for various chemicals of daily use. State in brief the method of pre…
• Design an experimental set-up to demonstrate that ''Alcohol and glucose contain hydrogen but are not categori…
• An aqueous solution of a salt turns blue litmus to red. The salt could be the one obtained by the reaction of…
• Four solutions, namely glucose, alcohol, hydrochloric acid and sulphuric acid filled in four separate beakers…
• Answer the following:
• Write the common name and the chemical name of the compound CaSO₄·½H₂O. Write the method of its preparation.…
• The salt present in tooth enamel is :
• An aqueous solution of sodium chloride is prepared in distilled water. The pH of this solution is :
• A few crystals of ferrous sulphate were taken in a dry boiling tube and heated. Tiny water droplets were obse…
• When the acid present in tamarind is mixed with a base, a mixture is produced. When the base is mixed into kn…
• In the given experimental set-up, if the experiment is carried out separately with each of the following solu…
• Answer the questions based on the following case:
• When Sodium bicarbonate reacts with dilute hydrochloric acid, the gas evolved is :
• Acid present in tomato is :
• Sodium hydroxide is termed an alkali while Ferric hydroxide is not because :
• The name of the salt used to remove permanent hardness of water is :
• (B) The industrial process used for the manufacture of caustic soda involves electrolysis of an aqueous solut…
• Answer the following: Suggest a safe procedure of diluting a strong concentrated acid.
• Answer the following: Name the salt formed when sulphuric acid is added to sodium hydroxide and write its pH.
• Answer the following: Dry HCl gas does not change the colour of dry blue litmus paper. Why ?
• Select a pair of olfactory indicators from the following :
• Fresh milk has a pH of 6. To delay its curdling, a chemical substance is added to it, which is :
• Hydronium ions are formed by the reaction between :
• When X is heated at 373 K, it loses water molecules and gets converted to Y. Y is used to keep things dry. (i…
• Two solutions M and N give Red and Blue colour respectively with a universal indicator. (i) In which solution…
• Answer the following : Sometimes the pH of our mouth gets lower than 5·5. Why ?
• In order to prepare dry hydrogen chloride gas in humid atmosphere the gas produced is passed through a guard…
• Assertion (A) : Concentrated nitric acid is diluted by adding water slowly to acid with constant stirring. Re…
• Read the source and answer the questions that follow.
• A common feature observed in the crystals of washing soda, copper sulphate, gypsum and ferrous sulphate is th…
• Write chemical formula of washing soda. How is it obtained from baking soda? List two uses of washing soda.
• You have three aqueous solutions A, B and C as given below : A - Potassium nitrate B - Ammonium chloride C -…
• Juice of tamarind turns blue litmus to red. It is because of the presence of a chemical compound called
• The water of crystallization is present in (i) Bleaching Powder (ii) Plaster of Paris (iii) Washing Soda (iv)…
• State the chemical property in each case on which the following uses of baking soda are based upon : (i) as a…
• Write chemical equations to show what happens when an acid reacts with a (i) metal (ii) base and (iii) carbon…
• Consider the following compounds : FeSO₄ ; CuSO₄ ; CaSO₄ ; Na₂CO₃ The compound having maximum number of water…
• Answer the following :
• Juice of tamarind turns blue litmus to red. It is because of the presence of an acid called :
• Read the source and answer the sub-parts that follow.
• Select a pair of natural indicator from the following :
• A chemical compound used in glass, soap and paper industries is
• Answer the following:
• Name and state in brief the process which is used to prepare sodium hydroxide from sodium chloride. In this p…
• The table below has information regarding pH and the nature (acidic/basic) of four different solutions. Which…
• Select washing soda from the following :
• Answer the following:
• Answer the following:
• Give reasons for the following : The path of a beam of light passing through a colloidal solution is visible.
• Few drops of aqueous solution of ammonium chloride are put on a universal indicator paper. The paper turns pi…
• Two salts 'X' and 'Y' are dissolved in water separately. When phenolphthalein is added to these two solutions…
• Consider the following chemical equation I and II I. Mg + 2HCl ⟶ MgCl₂ + H₂ II. NaOH + HCl ⟶ NaCl + H₂O The c…
• Assertion (A) : It is advised that while diluting an acid one should add water to acid and not acid to water…
• A substance 'X' is used as a building material and is insoluble in water. When it reacts with dil. HCl, it pr…

Chemistry · Chapter 3: Metals and Non-metals (78)

• Which one of the following metals does not react with cold water ?
• Alloys are homogeneous mixture of metal with a metal or non-metal. Which among the following alloys contain n…
• Which of the following is a poor conductor of electricity ?
• When an element 'X' reacts with water, it starts floating. Identify the element 'X' :
• Answer the following : What are amphoteric oxides ?
• Read the following passage and answer the questions given below :
• Which of the following is an amphoteric oxide ?
• Attempt option (A):
• Attempt option (B):
• When Mg metal is treated with hot water, it starts floating on the surface of the water. The reason for its d…
• Read the following passage and answer the questions that follow :
• Attempt either (a) or (b) : (a) (i) Write one example each of one metal that is so soft that it can be cut wi…
• Attempt either (a) or (b) : (b) Give reasons :
• The reaction of calcium with cold water is :
• When zinc reacts with NaOH, the product formed is :
• Show the formation of the following ionic compounds by transfer of electrons between the combining atoms : (G…
• Read the following passage and answer the questions that follow :
• The products formed when Aluminium and Magnesium are burnt in the presence of air respectively are :
• Reaction between two elements A and B, forms a compound C. A loses electrons and B gains electrons. Which one…
• The metals obtained from their molten chlorides by the process of electrolytic reduction are :
• Answer the following :
• Answer the following :
• Aluminium powder is used in thermit welding because :
• Two metals zinc and tin are dissolved separately in definite proportions in molten copper (the primary metal)…
• Assertion (A) : The metals high up in the reactivity series cannot be obtained from their compounds by heatin…
• Answer the following: Name the method used for refining silver.
• Write the electron-dot structures of (i) sodium, and (ii) oxygen. Using these structures, show the formation…
• The most common method of extraction of metals from their oxide ores is :
• Assertion (A) : Hydrogen gas is not evolved when a metal reacts with nitric acid. Reason (R) : Nitric acid is…
• Answer the following :
• Answer the following :
• Answer the following :
• The metals which are found in both free state as well as combined state are :
• Assertion (A) : The extraction of metals from their sulphide ores cannot take place without roasting of the o…
• Answer the following questions :
• A metal is used in the thermite process. When heated with air, it gives an oxide which is amphoteric in natur…
• Name the ore of mercury and state the form in which it is found in nature. Write the chemical equations along…
• When zinc reacts with sodium hydroxide, the product formed is :
• Among the following, the metal with lowest density is :
• The number of electrons in the outermost shell of the atom of a non-metal can be :
• Assertion (A) : Sodium oxide is an amphoteric oxide. Reason (R) : Metal oxides which react with both acids as…
• Answer the following:
• With the help of suitable chemical equations, list the two main differences between roasting and calcination.…
• A metal ribbon 'X' burns in oxygen with a dazzling white flame forming a white ash 'Y'. The correct descripti…
• Read the following and answer the questions:
• Which of the following statements is true for an amphoteric oxide ?
• Assertion (A) : In the following reaction ZnO + C → Zn + CO ZnO undergoes reduction. Reason (R) : Carbon is a…
• Read the case carefully and answer the questions that follow.
• The property by virtue of which a solid material can be drawn into thin wires is called :
• Show the formation of magnesium chloride by electron transfer. Write the name of the cation and anion present…
• How is zinc extracted from its ore? Name the processes involved in the extraction and write chemical equation…
• Design an activity to show that metals are good conductors of heat and have high melting points.
• A metal, M, displaces iron from aqueous solution of ferrous sulphate but fails to do so in case of aqueous so…
• A metal, 'X', on treatment with sodium hydroxide liberates a gas 'G'. It also liberates the same gas, 'G' on…
• During electrolytic refining of copper, the anode, the cathode and the electrolyte used respectively are
• Observe the following diagram showing an experiment to determine the conditions under which a metal 'M' corro…
• Answer the following about ionic compounds.
• Read the source and answer the sub-parts that follow.
• A metal and a non-metal that exists in liquid state at the room temperature are respectively :
• Oxides of aluminium and zinc are :
• Assertion (A) : Hydrogen gas is not evolved when zinc reacts with nitric acid. Reason (R) : Nitric acid oxidi…
• Read the source given and answer the questions that follow :
• The oxide which can react with HCl as well as KOH to give corresponding salt and water is
• Consider the following cases : (a) CaSO₄ + Al ⟶ (b) CuSO₄ + Ca ⟶ (c) FeSO₄ + Cu ⟶ (d) ZnSO₄ + Mg ⟶ The cases…
• Assertion (A) : Different metals have different reactivities with water and dilute acids. Reason (R) : Extrac…
• It is observed that Calcium on reaction with water floats on its surface. Explain why it happens. Also write…
• Draw a labelled diagram to show electrolytic refining of copper. State what happens when electric current is…
• Assertion (A) : A piece of Zinc metal gets reddish brown coating when kept in copper sulphate solution for so…
• State reasons for the following : Zinc oxide is an amphoteric oxide.
• State reasons for the following : Sodium metal is stored in bottle filled with kerosene oil.
• State reasons for the following : In the reactions of nitric acid with metals, generally hydrogen gas is not…
• State giving reason the reduction process to obtain the following metals from their compounds : (i) Mercury,…
• State giving reason for the change in appearance observed when each of the following metal is exposed to atmo…
• A metal 'X' is used in thermite process. When X is burnt in air it gives an amphoteric oxide 'Y'. 'X' and 'Y'…
• Read the passage and answer the following:
• Metal oxides generally react with acids, but few oxides of metal also react with bases. Such metallic oxides…
• Bronze is an alloy of
• A metal 'M' on reacting with dilute acid liberates a gas 'G'. The same metal also liberates gas 'G' when reac…

Chemistry · Chapter 4: Carbon and its Compounds (70)

• While washing dirty clothes by soap, micelles are formed. Select the correct statement about micelles.
• Assertion (A) : Pure ethanoic acid is also known as glacial acetic acid. Reason (R) : Pure ethanoic acid ofte…
• The formula of functional group for aldehyde is :
• Assertion (A) : Carbon shares its valence electrons with other atoms of carbon or with atoms of other element…
• (i) Give reasons for the following : (I) Covalent compounds are poor conductor of electricity. (II) Soap does…
• Mohan heated ethanol with a compound 'X' in the presence of a few drops of conc. H₂SO₄ and observed a sweet s…
• Which of the following set of compounds does not belong to same homologous series ?
• Which of the following will not undergo addition reaction ?
• Answer the following questions based on the passage:
• Assertion (A) : Carbon compounds can form chains, branched and ring structures. Reason (R) : Carbon exhibits…
• Attempt either (a) or (b) : (a) A carbon compound 'P' of molecular formula C₂H₆O is found to be neutral when…
• Attempt either (a) or (b) : (b) (i) Write the structural formula of benzene. (ii) State the reason why carbon…
• Consider the structures 'X' and 'Y' given below : X: H–C–C–C–C–H (butane, C₄H₁₀, straight chain) Y: H–C–(C wi…
• Assertion (A) : There are large number of compounds with many carbon atoms linked to each other. Reason (R) :…
• Attempt either (a) or (b) :
• Attempt either (a) or (b) :
• Answer the following :
• Answer the following :
• Answer the following:
• Answer the following:
• Answer the following:
• Given below are the structures of some hydrocarbons. Select the two structures which are related to each othe…
• Choose the incorrect statement about the common reaction used in hydrogenation of vegetable oils.
• Read the following case and answer the questions that follow.
• The number of single and double bonds present in a molecule of benzene (C₆H₆) respectively, are :
• Distinguish between a saturated and an unsaturated hydrocarbon by flame test. List the products of combustion…
• Why is the conversion of ethanol to ethanoic acid an oxidation reaction ? Name the oxidising agent used in th…
• Assertion (A) : Some vegetable oils are healthy. Reason (R) : Vegetable oils generally have long unsaturated…
• The melting and boiling points of carbon compounds are generally low and they are largely non-conductors of e…
• Answer the following questions :
• The total number of electrons shared in the formation of an ethyne molecule is :
• (a) An acid X reacts with an alcohol Y in the presence of a catalyst acid to form a substance Z that has a pl…
• (b) Answer the following:
• The electron dot structure of chlorine molecule is :
• (A) (i) Draw the structure of the following compounds : (a) Butanoic acid (b) Chloropentane (ii) How are stru…
• (B) (i) What happens when a small piece of sodium is dropped in ethanol ? Write the equation for this reactio…
• The correct representation of covalent bonding in an oxygen molecule is :
• A neutral organic compound X (molecular formula C₂H₆O) on reacting with acidified K₂Cr₂O₇ forms another organ…
• Carry out the following conversions, stating the condition(s) for each :
• Answer the following:
• Draw two different possible structures of a saturated hydrocarbon having four carbon atoms in its molecule. W…
• Answer the following:
• Draw the electron dot structure of the following: Cyclohexane
• Draw the electron dot structure of the following: Butane
• State the reason why (i) carbon compounds have low melting and boiling points. (ii) carbon compounds do not c…
• What is a homologous series? Find the difference in molecular mass between the two consecutive members of a h…
• Select from the following a hydrocarbon having one C–C bond and one C≡C bond :
• A carbon compound 'A' on heating with excess conc. H₂SO₄ forms a compound 'B', which on addition of one mole…
• A carbon compound 'A' is widely used as a preservative in pickles and has a molecular formula C₂H₄O₂. This co…
• If we make carbon skeleton with four carbon atoms, the two different possible skeletons will be
• Answer the following about carbon compounds.
• Answer the following about ethyne and ethanol.
• Answer the following sub-parts based on the given passage about combining capacity and valence electrons.
• A Hydrocarbon which does not belong to the same homologous series of carbon compounds is
• Assertion (A) : Carbon and its compounds are our major sources of fuels. Reason (R) : Most of the carbon comp…
• Name an alcohol and a carboxylic acid having two carbon atoms in their structures. Draw their structures and…
• What are soaps ? Write the structure of a soap molecule. Explain the cleansing action of a soap. Why are soap…
• Carbon compounds : (i) are good conductors of electricity. (ii) are bad conductors of electricity. (iii) have…
• Answer the following about carbon compounds :
• Answer the following :
• Consider the following statements about homologous series of carbon compounds : (a) All succeeding members di…
• Answer the following :
• Answer the following :
• The structural formula of Cyclohexane is
• Which one of the following hydrocarbons is different from the others ?
• Read the source and answer the sub-parts that follow.
• Consider the structures of the three cyclic carbon compounds A, B and C given below and select the correct op…
• A saturated organic compound 'A' belongs to the homologous series of alcohols. On heating 'A' with concentrat…
• Answer the following:
• Assertion (A) : Melting point and boiling point of ethanol are lower than that of sodium chloride. Reason (R)…

Biology · Chapter 5: Life Processes (110)

• Observe the given figure and select the statement that correctly states how these fungi obtain nutrition.
• In human beings the oxygen rich blood is pumped out to the body by :
• "Transpiration in plants is a necessary evil." Comment on the statement giving two reasons.
• Varun is diabetic. His latest ultrasound reports showed a blockage in his pancreatic duct. How will this affe…
• Option (A):
• Option (B):
• Which structure in a leaf is mainly responsible for gaseous exchange ?
• Pancreas secretes pancreatic juice which contain certain enzyme that helps in digestion of food. Choose the c…
• Assertion (A) : In human beings, the respiratory pigment is haemoglobin present in red blood cells. Reason (R…
• What is the function of diaphragm in human respiratory system ? Where is it present in human body ?
• Give differences between the following : Nephron and neuron
• Identify the part that controls the closing and opening of the stomatal pore in leaves of plants. Select the…
• Choose the equation of reaction that correctly represents anaerobic respiration in muscles :
• Assertion (A) : The peristaltic movements occur all along the gut. Reason (R) : The lining of the gut has mus…
• Give a diagrammatic representation of nutrition in Amoeba.
• Briefly mention the steps in double-circulation through human heart.
• Answer the following questions based on the passage:
• The carbohydrates, which are not used immediately in plants, are stored in the form of 'a', which serves as a…
• The following events occur during the process of photosynthesis. Choose the option that indicates the correct…
• Assertion (A) : Blood plasma transports carbon dioxide in dissolved form, while oxygen is transported by resp…
• Complete the pathways given below, showing the breakdown of glucose. Identify 'A', 'B', 'C', 'D', 'E' and 'F'.
• Pravin was given a list of characteristics associated with the process of anaerobic respiration in humans, in…
• Assertion (A) : The basic filtration unit in the kidneys, like in the lungs, is a cluster of very thin-walled…
• What kind of respiration provides more energy and why ?
• Separation of right side and left side of the heart is useful to keep oxygenated and deoxygenated blood from…
• In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous…
• Read the following passage and answer the questions that follow :
• Secretion of less saliva in mouth will effect the conversion of :
• The breakdown of glucose has taken the following pathway : Glucose →(a) Pyruvate + Energy →(b) Lactic acid +…
• Besides minimising the loss of blood, why is it essential to plug any leak in a blood vessel ? Name the compo…
• Answer the following :
• Read the passage carefully and answer the questions that follow.
• The opening and closing of stomata is regulated by :
• One-cell thick blood vessels are known as :
• Assertion (A) : Animals will not get energy if they eat (consume) coal as food. Reason (R) : Specific enzymes…
• Answer the following:
• Answer the following:
• The gastric glands present in the wall of the stomach release :
• State the main function of veins in human circulatory system. Why do they not need thick walls ?
• On the basis of the characteristics of the processes given in the brackets in each case, differentiate betwee…
• On the basis of the characteristics of the processes given in the brackets in each case, differentiate betwee…
• On the basis of the characteristics of the processes given in the brackets in each case, differentiate betwee…
• In human beings, when the process of digestion is completed, the (i) proteins, (ii) carbohydrates, and (iii)…
• Assertion (A) : In the human heart ventricles have thicker muscular walls than atria. Reason (R) : Ventricles…
• Answer the following:
• Answer the following questions :
• The process in which transport of soluble products of photosynthesis takes place in plants is known as :
• Answer either (a) or (b):
• Design an experiment to demonstrate that carbon dioxide is essential for photosynthesis. Write the observatio…
• Answer the following parts:
• Sphincter muscles are present at the exit of :
• In the following diagram, identify the cells through which massive amounts of gaseous exchange takes place fo…
• During vigorous exercise, the occurrence of cramps in the outer muscles of an athlete is due to the conversio…
• Answer the following:
• Answer the following:
• (b) Write in sequence the steps for experimental verification of the fact that sunlight is essential for phot…
• Opening and closing of stomata is due to :
• Assertion (A) : The inner walls of the small intestine have finger like projections called villi which are ri…
• Write one specific function each of the following organs in relation with excretion in human beings : (i) Ren…
• Write one specific function each of the following organs in relation with excretion in human beings : (i) Ren…
• Write one specific function each of the following organs in relation with excretion in human beings : (i) Ren…
• Write one specific function each of the following organs in relation with excretion in human beings : (i) Ren…
• Two green plants are kept separately in oxygen free containers, one in the dark and other in sunlight. It was…
• (A) (i) How does Paramecium obtain its food ? (ii) List the role of each of the following in our digestive sy…
• (B) (i) What is double circulation ? (ii) Why is the separation of the right side and the left side of the he…
• The process in which loss of water in the form of vapours from the aerial parts of plants takes place is X, w…
• As compared to terrestrial organisms, the rate of breathing in aquatic organisms is :
• Assertion (A) : The walls of atria are thicker than those of the ventricles. Reason (R) : Ventricles have to…
• List the events in proper sequence that take place during the process of photosynthesis.
• Explain in brief two ways by which leaves of a plant help in excretion.
• In the process of digestion of food in human beings, two protein-digesting enzymes are secreted. Name the enz…
• Answer the following :
• The essential element taken up from the soil by the plants to synthesize proteins is :
• Select TRUE statements about lymph from the following : A. Lymph vessels carry lymph through the body and fin…
• Assertion (A) : In large animals, oxygen can reach different parts of the animal's body easily. Reason (R) :…
• "Plants use a variety of techniques to get rid of waste material." Justify this statement giving any four way…
• The digestion of food in human alimentary canal is a complex process. State the enzyme/salt present in the fo…
• Listed below are the steps of nutrition in Amoeba. Select the correct sequence of these steps : (i) Diffusion…
• In aerobic respiration, the steps are : breakdown of glucose to pyruvate and its further conversion to carbon…
• How is lymph formed? State its important function.
• Answer the following based on the figure of human nephron.
• Answer the following about respiration and energy.
• The basic filtration unit of the excretory system in human beings is :
• In human alimentary canal, the digestive juice secreted by the gastric glands are
• Assertion (A) : Xylem tissue moves water and minerals obtained from the soil by the roots. Reason (R) : Xylem…
• Name the blood vessel that brings (i) oxygenated blood (ii) deoxygenated blood, to the human heart. Also name…
• A stomata closes when : (i) it needs carbon dioxide for photosynthesis. (ii) it does not need carbon dioxide…
• Assertion (A) : The rate of breathing in aquatic organisms is much faster than in terrestrial organisms. Reas…
• State one role of each of the following in human digestive system :
• Answer the following about respiration :
• Which of the following statement(s) is (are) true about human heart ? (a) Right atrium receives oxygenated bl…
• In human respiratory system, when a person breathes in, the position of ribs and diaphragm will be :
• Photosynthesis takes place in the leaves and the food prepared by it reaches other parts of the plants. Name…
• Give reasons for the following :
• Answer the following :
• Which of the following statement (s) is (are) true about human heart ? (a) Right atrium receives oxygenated b…
• We water the soil but it reaches the topmost leaves of the plants. Explain in brief the process involved.
• Read the source and answer the sub-parts that follow.
• An organism which breaks down the food material outside the body and then absorbs it is
• Consider the following statements about small intestine and select the one which is NOT correct :
• Assertion (A) : Blood clotting prevents excessive loss of blood. Reason (R) : Blood clotting is due to blood…
• Name the type of blood (oxygenated / deoxygenated) transported by each of the following mentioning the path (…
• With the help of a schematic flow chart, show the breakdown of glucose in a cell to provide energy –
• Name the part of the human excretory system where nephrons are found. Write the structure and function of nep…
• Answer the following:
• Answer the following:
• In the given diagram of a closed stomata : (1), (2), (3) and (4) respectively are
• Assertion (A) : Amoeba takes in food using finger like extensions of the cell surface. Reason (R) : In all un…
• Give the name of the enzyme present in the fluid in our mouth cavity. State the gland which produces it. What…
• Explain the process of transport of oxygenated and deoxygenated blood in a human body.

Chemistry · Chapter 5: Periodic Classification of Elements [2022 syllabus - removed in 2023 CBSE rationalisation; retained for pre-2023 board questions] (4)

• The electrons in the atoms of two elements X and Y are distributed in three shells having 1 and 7 electrons r…
• Answer the following:
• State the criteria used by Mendeleev for creating his Periodic Table. Compare the position of isotopes in Men…
• In the following table, some elements have been arranged in a certain pattern. Identify the periodic law with…

Biology · Chapter 6: Control and Coordination (67)

• Following are the statements about the different parts of the brain. Select the correct statements. (i) The t…
• Sunil unconsciously touched the hot iron rod and immediately withdrew his hand. Which type of action is invol…
• Give reasons for the following : Adrenal gland is known as the stress gland of the body.
• Plants exhibit movements in response to various environmental stimuli to adopt and survive in their surroundi…
• Human brain has various parts or regions that help in different actions, responses and coordination. From the…
• Assertion (A) : Reflex actions do not involve thinking. Reason (R) : Most reflex actions are controlled by th…
• State two differences between the act of chewing food and salivation on sight of food.
• Give differences between the following : Sensory nerve and motor nerve
• Identify the endocrine gland that regulates the growth of human body.
• Which of the plant hormones are responsible for the following processes ? (i) Promote cell division (ii) Inhi…
• Identify the type of tropic movement that is responsible for the movement of the pollen tube towards an ovule…
• "The timing and the amount of hormone secreted by a gland are regulated in the human body." Justify this stat…
• Electrical impulse is an excellent means to transmit information in the animal body, but there are some limit…
• Read the following passage and answer the questions that follow :
• Walking in a straight line and riding a bicycle are activities which are possible due to coordination of whic…
• In a synapse, the chemical signal is transmitted from :
• The growth of tendrils in grapes plants is due to :
• The plant hormone whose concentration stimulates the cells to grow longer on the side of the shoot which is a…
• Plants have neither a nervous system nor muscles, even then they respond to stimuli. For example, the leaves…
• Observe the given figures A and B. When chhui-mui (sensitive) plant is touched, its leaves fold. This is due…
• Name the parts of hind-brain of the human brain. Which part of the hind-brain controls involuntary actions su…
• Answer the following: Define hormone.
• Answer the following: "Hormones should be secreted in precise quantities. We have a feedback mechanism throug…
• The part of the brain which maintains the posture and balance of the body is :
• The plant hormone present in greater concentration in the areas of rapidly dividing cells is :
• Assertion (A) : In our actions of writing or talking, our nervous system communicates with the muscles. Reaso…
• Read the following case and answer the questions that follow.
• A plant growth inhibitor hormone which causes wilting of leaves is called :
• (i) Define a reflex arc. Why have reflex arcs evolved in animals ? Trace the sequence of events which occur,…
• (i) Leaves of chhui-mui plant begin to fold up and droop in response to a stimulus. Name the stimulus and wri…
• The correct sequence of events that occur when a person unknowingly touches a hot object is :
• The sense organ in which olfactory receptors are present is :
• Taking the example of any two animal hormones along with their gland of secretion, explain how these hormones…
• Name the hormone released and the gland which secretes it in human beings during scary situations. How does t…
• Answer the following:
• Answer the following:
• In plants the role of cytokinin is :
• (A) Name the part of brain which is responsible for the following actions : (i) Maintaining posture and balan…
• (B) Where are auxins synthesized in a plant ? Which organ of the plant shows : (i) Positive phototropism (ii)…
• The part in which gustatory receptors are present in our body is :
• Write the name and function of parts (i) and (ii) in the diagram of a neuron given below.
• State two limitations of electrical impulses in multicellular organisms. Why is chemical communication better…
• Read the source and answer the questions that follow.
• Which among the following is not a neural action controlled by the part of human brain labelled 'X' in the fi…
• The plant hormones promoting rapid cell division in seeds and wilting of leaves respectively are
• Answer the following about chemical control in organisms.
• Answer the following about voluntary action and reflex action.
• A pair of endocrine glands located in the human brain is
• Answer the following about the human brain.
• Read the source and study the figure, then answer the sub-parts that follow.
• In a nerve cell, the site where the electrical impulse is converted into a chemical signal is known as :
• How is the movement of leaves of a sensitive plant different from the downward movement of the roots ?
• There is a hormone which regulates carbohydrate, protein and fat metabolism in our body. Name the hormone and…
• Define reflex action. With the help of a flow chart show the path of a reflex action such as sneezing.
• Select out of the following a gland which does NOT occur as a pair in the human body :
• Answer the following :
• Answer the following :
• Select from the following a plant hormone which promotes cell division.
• Where are auxins synthesized ? How do they promote phototropism ?
• Answer the following:
• Select from the following the correct statement about tropic movement in plants :
• Answer the following:
• Walking in a straight line and riding a bicycle are the activities which are possible due to a part of the br…
• List two differences between the movement of leaves of a sensitive plant and the movement of a shoot towards…
• What happens at synapse between two neurons ? State briefly.
• Name the gland and the hormone secreted by it in scary situations in human beings. List any two responses sho…
• In the given diagram

Biology · Chapter 7: How do Organisms Reproduce? (86)

• If the part 'P' of the flower is removed, which of the following processes will not take place ?
• Assertion (A) : Variations are not often seen in off-springs produced by asexual reproduction. Reason (R) : D…
• Give reasons for the following : Prenatal sex determination is banned in India.
• Give reasons for the following : Vegetative propagation is advantageous in some plants.
• Identify the type of reproduction shown in the diagram given below :
• Identify the correct statement for spirogyra, leishmania and hydra :
• State two differences between pollination and fertilization.
• Draw a neat diagram to show germination of pollen on the female reproductive part of the flower. Name and lab…
• Given below are certain situations. Analyse each and describe its possible impact : (i) A population of bacte…
• Given below are certain situations. Analyse and describe what would happen when : (i) Spores are liberated fr…
• In human beings, the implantation of fertilised egg takes place in which part of female reproductive system ?
• Answer the following:
• Answer the following:
• Spirogyra, despite being a multi-cellular organism, still shows a simple reproductive method. Select the corr…
• Answer either (a) or (b) : (a) (i) Name an organ that helps in the formation of male germ cells in humans and…
• Radha has three children. She does not want to have more children. Radha visits a nearby hospital, to know th…
• Observe the given diagram and answer the questions that follow : (i) Give the name of the structure and type…
• Observe the given diagram and answer the questions that follow : (i) Give the name and type of reproduction s…
• The correct/true statement(s) for a bisexual flower is/are : (i) They possess both stamen and pistil. (ii) Th…
• Draw labelled diagrams to show different stages of budding in Hydra.
• Answer the following :
• Answer the following :
• Bryophyllum produces new plant through :
• The number of chromosomes in a cell division is halved. This kind of cell division is observed in :
• Write one function each of the following, in a seed : (i) Seed coat (ii) Cotyledon (iii) Radicle (iv) Plumule
• Write the main steps to culture yeast in the laboratory.
• Read the case carefully and answer the questions that follow.
• Match Column-I with Column-II and select the correct option from the choices provided. Column-I: a. Site of f…
• Select a pair of bisexual flowers from the following :
• Answer the following based on the diagram given :
• Answer the following based on the diagram given :
• The plants that can be raised by the method of vegetative propagation are :
• The part of seed which is a source of food during germination of seed is :
• A zygote is formed by the fusion of a male gamete and a female gamete. The number of chromosomes in the zygot…
• The survival of a species is promoted through creation of variations. Illustrate with an example.
• Answer the following:
• The incorrect statement about placenta is :
• Select from the following the conditions responsible for the rapid spread of bread mould on a slice of bread…
• Some unicellular organisms such as Plasmodium and Leishmania differ in the manner in which they reproduce. Na…
• Answer the following questions :
• Plants which bear unisexual flowers are :
• Assertion (A) : When a bacterium divides into two, and the resultant two bacteria divide again, the four bact…
• Answer the questions based on the following case:
• Observe the following diagram and identify the process and its significance from the following options :
• The number of chromosomes in parents and offsprings of a particular species undergoing sexual reproduction re…
• Answer the following: (i) Name and explain the two modes of asexual reproduction observed in hydra. (ii) What…
• The bacterial and the viral infections that may be caused due to unsafe sex respectively are :
• Answer the following :
• Answer the following :
• Read the case carefully and answer the questions that follow.
• Answer the following:
• Which one of the two multicellular organisms Spirogyra and Planaria reproduces by regeneration and why ? Give…
• Answer the following:
• Suggest any two contraceptive methods to control the size of human population and explain them.
• Justify that the sex determination of a child is based on what they inherit from their father and not from th…
• Name the part/organ of the human female reproductive system
• Read the passage and answer the following questions:
• Plants like rose and banana have lost the capacity to produce :
• In a bisexual flower the male gametes are present in the :
• Answer the following:
• Answer the following:
• The modes of reproduction in Spirogyra and Planaria respectively are
• Assertion (A) : The embryo gets nutrition from the mother's blood with the help of a special tissue called pl…
• Give reasons :
• Answer the following about fertilisation in flowering plants.
• Select the option having correct matching of the organism given in Column I with the mode of reproduction in…
• Explain the mechanism of inheritance used by sexually reproducing organisms to ensure the stability of DNA of…
• (a) Define Puberty. List any two changes seen in boys at the time of puberty. (b) Why are testes in human mal…
• (a) Name the part performing following functions in human female reproductive system : (i) production of eggs…
• Consider the following statements : (i) The sex of a child is determined by what it inherits from the mother.…
• In which of the following organisms, multiple fission is a means of asexual reproduction ?
• Answer the following about reproduction :
• Answer the following :
• Identify the mode of asexual reproduction in the following organism :
• "Stability of DNA in a species is ensured during sexual reproduction." Justify the statement.
• Explain the events that take place once a sperm reaches the oviduct till it becomes a foetus. Write the role…
• Read the source and answer the sub-parts that follow.
• Part(s) of a flower which attracts insects for pollination is (are)
• Assertion (A) : Offsprings produced by asexual reproduction are genetically similar to the parents. Reason (R…
• In human beings, the probability of getting a male or a female child is 50%. Explain with the help of a flow…
• Answer the following:
• Answer the following:
• Select the INCORRECT match (between the plant and its vegetative part) from the following :
• Answer the following:
• Choose the correct order of the stages of binary fission in Leishmania.
• Consider the following three flowers namely X, Y and Z. Which flower(s) would develop into a fruit ?

Biology · Chapter 8: Heredity (55)

• Identify the traits that cannot be transmitted from parents to the offsprings : (i) Swimming technique (ii) B…
• Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds were crossed…
• Study the given table and answer the following questions :
• Sex is determined by different factors in various species. However, in human beings, it is determined genetic…
• Mendel took garden pea plants with different characteristics, such as height to study the inheritance pattern…
• When a human egg is fertilized by a sperm having 'Y' chromosome, the zygote has the following combination of…
• Assertion (A) : Bacteria that can withstand heat have better chances of survival in a heat wave. Reason (R) :…
• Based on Mendel's experiment show the cross between round, yellow seeds of pea plant (RRYY) with wrinkled and…
• The genotype of green stemmed tomato plant is denoted by 'GG' and that of purple stemmed tomato plant as 'gg'…
• "Variation is useful for the survival of species over time." Explain this statement with the help of an examp…
• Answer the following :
• Show the cross and observations made by Mendel when he crossed pure tall pea plant with a pure short pea plan…
• If pea plants with round and green seeds (RRyy) are crossed with pea plants having wrinkled and yellow seeds…
• Assertion (A) : A human child bears all the basic features of human beings. Reason (R) : It looks exactly lik…
• Answer the following :
• Assertion (A) : A mango seed will germinate to form a mango tree. Reason (R) : Heredity determines the proces…
• The lowest part of the ear called earlobe, is closely attached to the side of the head in some of us (Figure…
• Answer the following :
• A pure pea plant having round (R), yellow (Y) seeds is crossed with another pure pea plant having wrinkled (r…
• List two differences between dominant traits and recessive traits. What percentage of pea plants in the F2 ge…
• Assertion (A) : Sex of the children will be determined by what they inherit from their mother. Reason (R) : W…
• Mendel crossed pure tall pea plants (TT) with pure short pea plants (tt) and obtained F₁ progeny. When the pl…
• When a sperm carrying the Y chromosome fertilises an egg, the resulting zygote would have the following combi…
• Mendel crossed a pure tall pea plant (TT) with a pure short pea plant (tt) and obtained all tall plants in F1…
• A cross between pea plant with white flowers (vv) and pea plant with violet flowers (VV) resulted in F2 proge…
• Assertion (A) : In humans, if gene (B) is responsible for black eyes and gene (b) is responsible for brown ey…
• Read the following and answer the questions:
• Consider the following two statements : (i) The trait that expresses itself in F1 generation. (ii) The trait…
• Assertion (A) : Human populations show a great deal of variations in traits. Reason (R) : All variations in a…
• Read the case carefully and answer the questions that follow.
• What is variation ? List two main reasons that may lead to variation in a population.
• Answer the following:
• Read the passage and answer the following questions:
• Mendel crossed two pea plants with two visible contrasting characteristics and found that there were no half-…
• Justify that the sex determination of a child is based on what they inherit from their father and not from th…
• How did Mendel's experiments show that traits are inherited independently? Explain.
• When a pure-tall pea plant is crossed with a pure-dwarf pea plant, the percentage of tall pea plants in F₁ an…
• Assertion (A) : In reptiles, the temperature at which the fertilized eggs are kept decides the sex of the off…
• Explain with the help of a flow chart that in human beings father is responsible for the sex (male or female)…
• Answer the following sub-parts based on the given passage about chromosomes and sex determination.
• A tall pea plant with round seeds (TTRR) is crossed with a short pea plant with wrinkled seeds (ttrr). The F₁…
• "Proteins control the expression of various characters." Explain this statement by taking an example of "tall…
• The gene combination of purple flowered pea plants is denoted as (WW) and that of white flowered pea plants a…
• Consider the following statements : (i) The sex of a child is determined by what it inherits from the mother.…
• Chromosomes : (i) carry hereditary information from parents to the next generation. (ii) are thread like stru…
• Read the source given and answer the questions that follow :
• A cross made between two pea plants produces 50% tall and 50% short pea plants. The gene combination of the p…
• Assertion (A) : Human female has a perfect pair of sex chromosome. Reason (R) : Sex chromosome contributed by…
• In an experiment to study independent inheritance of two separate traits : shape and colour of seeds, the rat…
• A cross between two tall pea plants resulted in offsprings having a few dwarf plants. The gene-combination of…
• List any two pairs of visible contrasting characters of garden pea plants used by Mendel for his experiments…
• The statement that correctly describes the characteristic(s) of a gene is :
• Assertion (A) : Genes inherited from the parents decide the sex of a child. Reason (R) : X chromosome in a ma…
• Read the passage and answer the following:
• In an experiment with pea plants, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio o…

Physics · Chapter 9: Light – Reflection and Refraction (69)

• Answer the following :
• The above ray diagram is to show image formation by a reflecting telescope. Reflecting telescope revolutioniz…
• A convex lens of focal length 15 cm, is forming a real image. If the size of image is same as the size of obj…
• The given figure shows image formation by a lens. Analyse the figure and answer the following questions :
• Read the following passage and answer the questions given :
• Rays from the sun converge at a point 25 cm behind a convex lens. The distance at which an object be placed i…
• Answer the following:
• Answer the following:
• From the following options choose the one which gives negative magnification greater than one :
• With the help of the given ray diagram, calculate the refractive index of Medium 2 with respect to Medium 1.…
• Answer the following :
• A ray of light enters into medium B from medium A as shown in the given figure :
• The variation of image distance (v) with the object distance (u) for a convex lens is given in the following…
• Mirror 'X' is used to concentrate sunlight in solar furnace and Mirror 'Y' is fitted on the side of the vehic…
• An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm. Use lens formula to fin…
• Draw ray diagrams to show the nature, position and relative size of the image formed by a convex mirror when…
• Answer the following :
• Answer the following :
• If the absolute refractive indices of two media X and Y are 6/5 and 4/3 respectively, then the refractive ind…
• An object is placed at a distance of 30 cm from the pole of a concave mirror. If its real and inverted image…
• In the given figure the angle of incidence and the angle of deviation respectively are :
• Out of the two lenses, one concave and the other convex, state which one will diverge a parallel beam of ligh…
• A ray of light after refraction from a convex lens emerges parallel to its principal axis. (i) Draw a labelle…
• A convex lens forms an 80 cm long image of a 20 cm long object which is kept at a distance of 60 cm from the…
• Absolute refractive index of water and glass is 4/3 and 3/2 respectively. If the speed of light in glass is 2…
• Draw a ray diagram to show the path of a ray of light falling obliquely on one of the refracting faces of a t…
• Answer the following :
• Answer the following :
• Absolute refractive index of glass and water is 3/2 and 4/3 respectively. If the speed of light in glass is 2…
• The variation of image distance (v) with object distance (u) for a convex lens is given in the following obse…
• (i) Define principal axis of a lens. Draw a ray diagram to show what happens when a ray of light parallel to…
• How will the image formed by a convex lens be affected, if the upper half of the lens is wrapped with a black…
• The heat produced at a point due to concentration of sunlight by a convex lens burns a paper.
• Answer the following questions :
• An object is placed in front of a convex mirror at infinity. According to the New Cartesian Sign Convention,…
• (a) A student has focussed the image of an object of height 3 cm on a white screen using a concave mirror of…
• (b) Define power of a lens. The focal length of a lens is −10 cm. Write the nature of the lens and find its p…
• Answer the following:
• (A) Define the following terms in the context of a diverging mirror : (i) Principal focus (ii) Focal length D…
• (B) An object of height 10 cm is placed 25 cm away from the optical centre of a converging lens of focal leng…
• The power of a lens is +4D. Find the focal length of this lens. An object is placed at a distance of 50 cm fr…
• Read the following and answer the questions:
• Answer the following :
• A convex lens can form a (i) real, inverted and magnified image as well as (ii) virtual, erect and magnified…
• Read the case carefully and answer the questions that follow.
• To get an image of magnification –1 on a screen using a lens of focal length 20 cm, the object distance must…
• An optical device 'X' is placed obliquely in the path of a narrow parallel beam of light. If the emergent bea…
• If we want to obtain a virtual and magnified image of an object by using a concave mirror of focal length 18…
• In order to obtain large images of the teeth of patients, the dentist holds the concave mirror in such a mann…
• The values of absolute refractive indices of kerosene and water are 1.44 and 1.33 respectively. Compare the t…
• Answer the following about refraction through three media.
• Analyse the following observation table showing variation of image distance (v) with object distance (u) in c…
• Identify from the following the ray diagram which shows the correct path of the reflected ray for the ray inc…
• Study the figure in which the path of a ray of light going from Medium 1 to Medium 2 is shown.
• A student placed a candle flame at different distances from a convex lens and focused its image on a screen.…
• At what distance from a convex lens should an object be placed to get an image of the same size as that of th…
• An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position of t…
• Study the data given below showing the focal length of three concave mirrors A, B and C and the respective di…
• State two laws of refraction of light.
• Define the term absolute refractive index of a medium. A ray of light enters from vacuum to glass of absolute…
• Upper half of a convex lens is covered with a black paper. Draw a ray diagram to show the formation of image…
• An object is placed at a distance of 30 cm from the optical centre of a concave lens of focal length 15 cm. U…
• Answer the following:
• Answer the following:
• Answer the following:
• Read the passage and answer the following:
• A student wants to obtain an erect image of an object using a concave mirror of 10 cm focal length. What will…
• A light ray enters from medium A to medium B as shown in the figure.
• OR alternative for Q25.

Physics · Chapter 10: The Human Eye and the Colourful World (64)

• The pair of eye parts responsible for admitting different amount of light in to the eyes is
• The vision defect which arises due to gradual weakening of the ciliary muscles and diminishing flexibility of…
• Explain the phenomenon of rainbow formation in the sky. Draw the labelled ray diagram in support of your expl…
• When you look at an object very close to your eyes, the :
• Assertion (A) : When rays of white light pass through a prism, on emerging they give spectrum of seven colour…
• A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in…
• To restore clear vision in persons whose size of the eye ball has reduced, he/she is suggested to use suitable
• Answer the following:
• Draw a ray diagram to show the correction of eye defect of an old man who can not see an object placed closer…
• Answer the following:
• A thin beam of white light falls on a face of a glass prism and a spectrum is obtained on a screen. Which of…
• How does the focal length of eye lens change as the distance of the object from the eyes is altered ? Explain.
• Why is the concave lens used as a corrective lens for a myopic eye ?
• What is scattering of light ? How is scattering of light different from reflection of light ? Explain.
• Observe the given ray diagram showing refraction through a prism and choose the correct option for colour of…
• What happens when light is scattered from (i) very fine particles and (ii) very large size particles of mediu…
• With the help of a ray diagram, explain any phenomenon of formation of spectrum in nature.
• Study the given diagram and answer the questions that follow :
• An old person is suffering from an eye defect caused by weakening of ciliary muscles and diminishing flexibil…
• Read the case carefully and answer the questions that follow.
• When a beam of white light passes through a region of very fine dust particles, the colour of light that scat…
• A student has difficulty in reading his textbooks but can read the blackboard clearly while sitting in the la…
• What is a rainbow ? Draw a labelled diagram to show its formation.
• When a beam of white light passes through a region having very fine dust particles, the colour of light mainl…
• A person suffering from presbyopia needs bifocal lens. If he needs two lens of power −4·0 dioptre and +2·0 di…
• Define the term power of accommodation of human eye. What happens to the image distance in the eye when we in…
• The phenomena of light involved in the formation of rainbow are :
• The colour of light for which the refractive index of glass is minimum, is :
• Study the diagram given below and answer the questions that follow : (i) Name the defect of vision depicted i…
• What is dispersion of white light ? State its cause. Draw a diagram to show dispersion of a beam of white lig…
• Assertion (A) : A person suffering from myopia cannot see the distant objects clearly. Reason (R) : A converg…
• (a) When and where does a rainbow appear in the sky ? Draw a labelled ray diagram to show its formation.
• (b) What is scattering of light ? Why does the clear sky appear blue ?
• (A) Observe the following diagram and answer the questions following it : (i) Identify the defect of vision s…
• (B) The colour of clear sky from the earth appears blue but from the space it appears black. Why ?
• Observe the following diagram showing an image formation in an eye : (a) Identify the defect of vision shown…
• Answer the following :
• Assertion (A) : When ciliary muscles contract, eye lens becomes thin. Reason (R) : Ciliary muscles control th…
• Draw a ray diagram to show the refraction of a ray of light passing through an equilateral glass prism. Mark…
• Name the type of lenses required by the persons for the correction of their defect of vision called presbyopi…
• Read the source and answer the questions that follow.
• The possible way to restore clear vision of those people whose eyeball has elongated is the use of suitable
• The power of a lens is –0.25 D. Based on this information, find out
• The part of human eye which controls the amount of light entering into it.
• Give reasons : (i) The sky appears dark to passengers flying at very high altitude. (ii) 'Danger' signal ligh…
• What is a rainbow ? "We see a rainbow in the sky only after the rainfall." Why ?
• A person uses lenses of +2.0 D power in his spectacles for the correction of his vision. (a) Name the defect…
• The lens system of human eye forms an image on a light sensitive screen, which is called as :
• Assertion (A) : The rainbow is a natural spectrum of sunlight in the sky. Reason (R) : Rainbow is formed in t…
• Study the diagram given below and answer the questions that follow :
• Consider the following statements in the context of human eye : (a) The diameter of the eye ball is about 2.3…
• Assertion (A) : Myopic eye cannot see distant objects distinctly. Reason (R) : For the correction of myopia c…
• Define the term power of accommodation of human eye. Write the name of the part of eye which plays a major ro…
• Draw a ray diagram to show the formation of a rainbow in the sky. On this diagram mark A – where dispersion o…
• The Phenomena of light involved in the formation of a rainbow in the sky are
• Assertion (A) : Red light signals are used to stop the vehicles on the road. Reason (R) : Red coloured light…
• When do we say that a particular person is suffering from hypermetropia ? List two causes of this defect. Nam…
• Name and explain the phenomenon of light due to which the path of a beam of light becomes visible when it ent…
• A narrow beam XY of white light is passing through a glass prism ABC as shown in the diagram. Trace it on you…
• It is observed that the power of an eye to see nearby objects as well as far off objects diminishes with age.
• Give reasons for the following : Danger signals installed at airports and at the top of tall buildings are of…
• Give reasons for the following : The sky appears dark to the passengers flying at very high altitudes.
• In the following diagram showing dispersion of white light by a glass prism, the colours 'P' and 'Q' respecti…
• In human eye the part which allows light to enter into the eye is –

Physics · Chapter 11: Electricity (85)

• A fuse in electric circuit is rated 4 A. Can it be used with an electric heater of rating 2 kW, 200 V ? Expla…
• Answer the following : Define volt, the unit of potential difference.
• Answer the following : Calculate the work done required to move an electron between two points A and B locate…
• On the basis of the given circuit arrangement, answer the following questions :
• Option (A):
• Option (B):
• The resistance of a wire of 0.01 cm radius and 1.0 cm length is 7 Ω. Calculate its resistivity.
• An electric heater is rated 220 V; 11 A. Calculate the power consumed if the heater is operated at 200 V.
• (i) Due to change in length and area of cross-section of a conductor, resistance of conductor changes while r…
• (i) How many bulbs of resistance 8 Ω each should be connected in parallel combination to draw a current of 2…
• Observe the given figure and identify the labelled parts P, Q, R and S :
• Answer the following: Why does an electric bulb become dim when an electric heater in parallel circuit is swi…
• Answer the following: How to connect three resistors each of resistance 8 Ω, so that the equivalent resistanc…
• Answer the following questions based on the passage:
• The values of current I flowing in a given resistor for the corresponding values of potential difference V ap…
• Read the following passage and answer the questions that follow :
• In which case/cases will the bulb glow considering that all other connections of electric circuit are complet…
• The correct way to connect an ammeter and a voltmeter in an electric circuit is :
• Answer the following :
• Consider the given electric circuit : Calculate the following :
• A wire of resistance R is cut into three equal parts. If these three parts are then joined in parallel, calcu…
• Define electric power. When do we say that the power consumed in an electric circuit is 1 watt ?
• Consider the following electric circuit :
• Answer the following :
• Read the passage carefully and answer the questions that follow.
• An electric bulb is connected to a power supply of 220 V. If the current drawn by the bulb from the supply is…
• Four identical resistors of 12 Ω each are connected in series to form a square ABCD as shown in the figure. T…
• Assertion (A) : Nichrome is an alloy which is commonly used in electrical heating devices such as electric ir…
• An electric kettle is rated 750 W; 220 V. Can this kettle be used in a circuit which has a fuse of current ra…
• Three resistors of 2 Ω, 3 Ω and 6 Ω are connected in (i) series, and (ii) parallel. Draw the arrangements of…
• A wire of length 'l' is gradually stretched so that its length increases to 3l. If its original resistance is…
• An electric kettle is rated 230 V; 1000 W. Calculate the resistance of its heating element when in operation.
• Read the following case and answer the questions that follow.
• Consider the following combinations of resistors : The combinations having equivalent resistance 1 Ω is/are :
• An electric iron of resistance 20 Ω draws a current of 5 A. The heat developed in the iron in 30 seconds is :
• Two wires A and B of same material, having same lengths and diameters 0·2 mm and 0·3 mm respectively, are con…
• On the basis of this circuit, answer the following questions :
• Assertion (A) : Electrons move from lower potential to higher potential in a conductor. Reason (R) : A dry ce…
• An electric source can supply a charge of 500 coulomb. If the current drawn by a device is 25 mA, find the ti…
• Answer the following parts:
• Answer the following parts:
• For verification of Ohm's law, we design an electrical circuit diagram in which we show the arrangement of di…
• In a resistive circuit if the current is increased to two times, the percentage change in the amount of heat…
• V–I graph for two conducting wires A and B are as shown. If both wires are of the same length and same diamet…
• Explain the meaning of overloading of an electrical circuit. List two possible causes due to which overloadin…
• Answer the questions based on the following electrical circuit diagram:
• Two LED bulbs of 12W and 6W are connected in series. If the current through 12W bulb is 0.06A the current thr…
• The resistance of a resistor is reduced to half of its initial value. If other parameters of the electrical c…
• (A) (i) Why is an alternating current (A.C.) considered to be advantageous over direct current (D.C.) for the…
• Answer the following:
• The expressions that relate (i) Q, I and t and (ii) Q, V and W respectively are (Here the symbols have their…
• An electric kettle consumes 1 kW of electric power when operated at 220 V. The minimum rating of the fuse wir…
• Answer the following :
• Answer the following:
• Answer the following:
• Answer the following:
• An electric heater rated 1100 W operates at 220 V. Calculate (i) its resistance, and (ii) the current drawn b…
• Calculate the equivalent resistance of the following electric circuit:
• Study the following electric circuit in which the resistors are arranged in three arms A, B and C:
• A piece of wire of resistance 'R' is cut lengthwise into three identical parts. These parts are then connecte…
• An electric bulb is rated 220 V; 11W. The resistance of its filament when it glows with a power supply of 220…
• The minimum number of identical bulbs of rating 4V; 6W, that can work safely with desired brightness, when co…
• The electrical resistivity of three materials A, B and C at 20°C is given below :
• Answer the following on Joule's heating and electric energy / resistance.
• The resistance of a wire of 0.01 cm radius is 7 ohms. If the resistivity of the material of the wire is 44 ×…
• Assertion (A) : In the common domestic circuits the earth wire is connected to a metallic plate buried deep i…
• Answer the following about electricity.
• Study the circuit shown in which two resistors X and Y of resistances 3 Ω and 6 Ω respectively are joined in…
• Show how you would connect three resistors each of resistance 6 Ω, so that the combination has a resistance o…
• In the given circuit calculate the power consumed in watts in the resistor of 2 Ω :
• Answer the following about electric power :
• Answer the following about electrical resistivity :
• The maximum resistance of a network of five identical resistors of 1/5 Ω each can be –
• Study the I-V graph for three resistors of resistances R₁, R₂ and R₃ and select the correct statement from th…
• Use Ohm's law to determine the potential difference across the 3 Ω resistor in the circuit shown in the follo…
• Read the source and answer the sub-parts that follow.
• In case of four wires of same material, the resistance will be minimum if the diameter and length of the wire…
• Explain in brief the function of an electric fuse in a domestic circuit. An electric heater of current rating…
• Answer the following:
• In a domestic circuit five LED bulbs are arranged as shown. The source voltage is 220 V and the power rating…
• If four identical resistors, of resistance 8 ohm, are first connected in series so as to give an effective re…
• In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have
• In the following diagram, the position of the needle is shown on the scale of a voltmeter. The least count of…
• Answer the following:
• Let the resistance of an electrical device remain constant, while the potential difference across its two end…

Physics · Chapter 12: Magnetic Effects of Electric Current (65)

• Assertion (A) : With the help of compass, magnetic field lines can be traced outside the bar magnet. Reason (…
• How is an electromagnet made ? Write any two ways by which the strength of electromagnet can be increased.
• Answer the following :
• Answer the following :
• Assertion (A) : The needle of a magnetic compass kept in strong external magnetic field, always aligns itself…
• Attempt option (A):
• Attempt option (B):
• Assertion (A) : Direction of force exerted on a current-carrying conductor placed in a magnetic field remains…
• Attempt either (a) or (b) : (a) (i) State the rule which gives the direction of force acting on a current-car…
• Attempt either (a) or (b) : (b) (i) Draw the pattern of magnetic field lines through and around a current-car…
• Assertion (A) : The needle of a compass, kept in an external magnetic field, always aligns itself in the Nort…
• Attempt either (a) or (b) :
• Attempt either (a) or (b) :
• Assertion (A) : No two magnetic field lines are found to cross each other. Reason (R) : The compass needle ca…
• The given figure shows the current passing through the straight conductor XY.
• Answer the following:
• Which one of the following statements is not true about a bar magnet ?
• The strength of magnetic field produced inside a long straight current carrying solenoid does not depend upon…
• Assertion (A) : Magnetic field lines around a bar magnet never intersect each other. Reason (R) : Magnetic fi…
• Consider a rectangular cardboard having two holes P and Q through which a current carrying circular loop has…
• A rectangular loop ABCD carrying a current I is situated near a straight conductor XY, such that the conducto…
• Assertion (A) : Magnetic field lines never intersect each other. Reason (R) : If they intersect, then at the…
• A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He spr…
• The current carrying device which produces a magnetic field similar to that of a bar magnet is :
• A uniform magnetic field exists in the plane of paper as shown in the diagram. In this field, an electron (e⁻…
• Answer the following parts:
• A positron enters a uniform magnetic field at right angles to it as shown. The direction of force experienced…
• Assertion (A) : Magnetic field lines do not intersect each other. Reason (R) : Magnetic field lines are imagi…
• The correct pattern of magnetic field lines of the field produced by a current carrying circular loop is :
• An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha p…
• Assertion (A) : A current carrying straight conductor experiences a force when placed perpendicular to the di…
• (B) For the current carrying solenoid as shown, draw magnetic field lines and give reason to explain that out…
• A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the fig…
• For a current in a long straight solenoid, N and S poles are created at the two ends. Among the following sta…
• Assertion (A) : Two magnetic field lines around a current carrying straight wire do not intersect each other.…
• Answer the following :
• Draw the pattern of the magnetic field produced around a vertical current carrying straight conductor passing…
• Answer the following:
• Answer the following:
• Read the passage and answer the following questions:
• What is a Solenoid? Draw the pattern of the magnetic field lines around a current carrying solenoid. Mark on…
• In the diagram given below, Coil 1 is connected in series with a battery and a plug key while Coil 2 is conne…
• In the figure given below, a simple electric motor is shown. As shown in the figure, the current in the coil…
• What are magnetic field lines. List two important properties of magnetic field lines.
• Answer the following:
• Answer the following:
• Assertion (A) : The pattern of the magnetic field of a solenoid carrying a current is similar to that of a ba…
• Answer the following about domestic electric circuits.
• Answer the following sub-parts based on the experiment and the magnetic field pattern shown.
• What are magnetic field lines ? How is the direction of magnetic field at a point determined ? Draw the patte…
• Why can't two magnetic field lines cross each other ? Draw magnetic field lines showing the direction of the…
• The pattern of the magnetic field produced inside a current carrying solenoid is :
• Answer the following about magnetic field lines :
• Name and state the rule to determine the direction of a :
• Strength of magnetic field produced by a current carrying solenoid DOES NOT depend upon :
• Assertion (A) : The deflection of a compass needle placed near a current carrying wire decreases when the mag…
• Draw a diagram to show the pattern of magnetic field lines on a horizontal sheet of paper due to a straight c…
• Draw a labelled diagram to show the pattern of magnetic field lines produced due to a current carrying straig…
• Name the device used to magnetise a piece of magnetic material. Draw a labelled diagram to show the arrangeme…
• The resultant magnetic field at point 'P' situated midway between two parallel wires (placed horizontally) ea…
• Assertion (A) : The strength of the magnetic field produced at the centre of a current carrying circular coil…
• Answer the following:
• Answer the following:
• The magnetic field inside a long straight current carrying solenoid :
• State the rule to determine the direction of a (a) magnetic field produced around a straight conductor carryi…

Biology · Chapter 13: Our Environment (73)

• Given below are some of the statements regarding our environment : (i) Change in our life-styles have resulte…
• Assertion (A) : Highest percentage of pesticides is found in tertiary consumers in a food chain. Reason (R) :…
• Explain why food chains generally consist of three or four steps.
• Which of the following group is not 'biodegradable' ?
• Given below is a pyramid showing various trophic levels in an ecosystem :
• Give differences between the following : Consumers and decomposers
• Which of the following is a non-biodegradable pollutant ?
• In an ecosystem, the decomposers perform an important role. Select the option indicating the role of decompos…
• Answer the following questions: Mention any one harmful effect of using plastic bags on the environment. Sugg…
• Answer the following questions: Paddy fields require a large amount of water. The pesticides and chemical fer…
• In the given figure, identify the trophic level having maximum concentration of harmful chemicals.
• Which of the following limits the number of trophic levels in a food chain ?
• Assertion (A) : There are generally a greater number of individuals at the lower trophic levels of an ecosyst…
• Suggest one best way to dispose of the following wastes :
• Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic lev…
• In accumulation of toxic substances at higher trophic levels of an ecosystem through the food chain, which of…
• Assertion (A) : Natural replenishment of soil will not take place in absence of microbes. Reason (R) : Microb…
• Answer the following :
• Which of the following groups do not constitute a food chain ? (i) Wolf, rabbit, grass, lion (ii) Plankton, m…
• The percentage of solar energy which is not converted into food energy by the leaves of green plants in a ter…
• Assertion (A) : The amount of ozone in the atmosphere began to drop sharply in the 1980s. Reason (R) : The ox…
• ''Excessive use of chemicals and pesticides in agriculture adversely effect the environment.'' Justify this s…
• Identify from the following a group containing all non-biodegradable substances.
• Write the essential function performed by ozone at the higher levels of the atmosphere. How is it formed in t…
• Other than the abiotic components, which of the given biotic components are not required to make an aquarium…
• Assertion (A) : Use of jute bags for shopping reduces pollution. Reason (R) : Jute is biodegradable and its b…
• Answer the following :
• Some wastes are given below : (i) Garden waste (ii) Ball point pen refills (iii) Empty medicine bottles made…
• Assertion (A) : Oxygen is essential for all aerobic forms of life. Reason (R) : Free oxygen atoms combine wit…
• Study the picture given below showing three food chains (a), (b) and (c) and answer the following questions :…
• Which one of the following is not a natural ecosystem ?
• Assertion (A) : Ozone layer protects the surface of the Earth from harmful UV radiations. Reason (R) : Chloro…
• Differentiate between food chain and food web. In a food chain consisting of deer, grass and tiger, if the po…
• We do not clean ponds or lakes but an aquarium needs to be cleaned regularly. Why ?
• Explain how some harmful chemicals enter our bodies through the food chain. Why is the concentration of these…
• Use of several pesticides which results in excessive accumulation of pesticides in rivers or ponds, is a matt…
• Write one difference between biodegradable and non-biodegradable wastes. List two impacts of each type of the…
• In the following food chain, if 50 J of energy was available to the hawk, how much energy would have been pre…
• Depletion of ozone layer is a cause of concern. Justify this statement.
• What is ozone ? How is it formed in the upper layers of the atmosphere ? How does ozone affect our ecosystem ?
• Answer the following:
• Answer the following: Name the group of organisms which form the first trophic level of all food chains. Why…
• Answer the following: Why are the human beings most adversely affected by bio-magnification ?
• Answer the following: State one ill-effect of the absence of decomposers from a natural ecosystem.
• Kulhads (disposable cups made of clay) and disposable paper cups both are used as an alternative for disposab…
• Human beings are most adversely affected by the Biological Magnification. State the reason. Why can ordinary…
• What are human-made ecosystems? Give an example. Can a human-made ecosystem become a self-sustaining ecosyste…
• In the food chains given below. Select the most efficient food chain in terms of energy :
• Which one of the following gets biomagnified at different levels in a food chain ?
• What are decomposers? Give two examples. State how they maintain a balance in an ecosystem.
• The examples of natural and manmade (artificial) ecosystems are respectively
• Human activities that are affecting the environment are :
• Assertion (A) : All organisms can make organic compounds like sugar and starch from inorganic substances usin…
• Answer the following about food chain and energy flow.
• Consider the following food chain : Grass → Grasshopper → Frog → Snake → Eagle If the amount of energy availa…
• The incorrect statement about ozone is
• Assertion (A) : Food web is a network of several food chains operating in an ecosystem. Reason (R) : Food web…
• We do not clean natural ponds or lakes whereas an aquarium or a swimming pool needs to be cleaned regularly.…
• Identify the food chain in which the organisms of the second trophic level are missing :
• Assertion (A) : Accumulation of harmful chemicals is maximum in the organisms at the highest trophic level of…
• Plants → Deer → Lion In the given food chain, what will be the impact of removing all the organisms of second…
• A gas 'X' which is a deadly poison is found at the higher levels of atmosphere and performs an essential func…
• Name the term used for the materials which cannot be broken down by biological processes. Give two ways by wh…
• Use of pesticides to protect our crops affect organisms at various trophic levels especially human beings. Na…
• A food chain will be more advantageous in terms of energy if it has
• Consider the following statements about ozone : (a) Ozone is poisonous gas. (b) Ozone shields the earth's sur…
• Assertion (A) : The waste we generate daily may be biodegradable or non-biodegradable. Reason (R) : The waste…
• What are decomposers ? List two consequences of their absence in an ecosystem.
• How do harmful chemicals get accumulated progressively at each trophic level in a food chain ?
• Answer the following:
• Answer the following:
• Study the given figure of a Food web and identify the primary consumer in the food web:
• Assertion (A) : The energy which passes to the herbivores does not come back to autotrophs. Reason (R) : The…