CBSE Class 10 Science Question Paper 2023

In the given experimental setup, it was observed that on passing the gas evolved in the reaction through solution 'X', solution 'X' first turns milky and then becomes colourless. The option that justifies the above observation is - 'X' is an aqueous solution of calcium hydroxide and

• (A) it turns milky due to the carbon dioxide gas released in the reaction, and after some time it becomes colourless due to the formation of calcium carbonate.
• (B) the solution turns milky due to the formation of calcium carbonate, and on passing excess carbon dioxide, it changes into colourless calcium hydrogen carbonate, which is soluble in water. ✓
• (C) the solution turns milky due to the passing of carbon dioxide, and thereafter, on passing more gas, it changes into sodium hydrogen carbonate, which is soluble in water.
• (D) the carbon dioxide gas released in the reaction turns lime water milky due to the formation of calcium hydrogen carbonate, and after some time the solution becomes colourless due to the formation of calcium carbonate, as it is soluble in water.

Answer (the board’s key): (B)

The emission of brown fumes in the given experimental set-up is due to

• (A) thermal decomposition of lead nitrate which produces brown fumes of nitrogen dioxide. ✓
• (B) thermal decomposition of lead nitrate which produces brown fumes of lead oxide.
• (C) oxidation of lead nitrate forming lead oxide and nitrogen dioxide.
• (D) oxidation of lead nitrate forming lead oxide and oxygen.

Answer (the board’s key): (A)

MnO_2 + x HCl -> MnCl_2 + y H_2O + z Cl_2. In order to balance the above chemical equation, the values of x, y and z respectively are :

• (A) 6, 2, 2
• (B) 4, 1, 2
• (C) 4, 2, 1 ✓
• (D) 2, 2, 1

Answer (the board’s key): (C)

The table given below provides information about the pH and nature (acidic/basic) of four different solutions. | Option | Solution | Colour of pH paper | Approximate value of pH | Nature of solution | | --- | --- | --- | --- | --- | | (a) | Lemon juice | Orange | 3 | Basic | | (b) | Milk of magnesia | Blue | 10 | Basic | | (c) | Gastric juice | Red | 6 | Acidic | | (d) | Pure water | Yellow | 7 | Neutral | Which option of this table is correct?

• (A) Lemon juice, Orange, 3, Basic
• (B) Milk of magnesia, Blue, 10, Basic ✓
• (C) Gastric juice, Red, 6, Acidic
• (D) Pure water, Yellow, 7, Neutral

Answer (the board’s key): (B)

A metal 'X' is used in thermite process. When X is burnt in air it gives an amphoteric oxide 'Y'. 'X' and 'Y' are respectively :

• (A) Fe and Fe_2O_3
• (B) Al and Al_2O_3 ✓
• (C) Fe and Fe_3O_4
• (D) Al and Al_3O_4

Answer (the board’s key): (B)

Select washing soda from the following :

• (A) NaHCO_3
• (B) Na_2CO_3.5H_2O
• (C) Na_2CO_3.10H_2O ✓
• (D) NaOH

Answer (the board’s key): (C)

Consider the structures of the three cyclic carbon compounds A, B and C given below and select the correct option from the following :

• (A) A and C are isomers of hexane and B is benzene.
• (B) A is an isomer of hexane, B is benzene and C is an isomer of hexene.
• (C) A is a saturated cyclic hydrocarbon and B and C are unsaturated cyclic hydrocarbons. ✓
• (D) A is cyclohexane and B and C are the isomers of benzene.

Answer (the board’s key): (C)

An organism which breaks down the food material outside the body and then absorbs it is

• (A) a plant parasite, Cuscuta
• (B) an animal parasite, Tapeworm
• (C) a bacteria, Rhizobium
• (D) a fungi, Rhizopus ✓

Answer (the board’s key): (D)

Consider the following statements about small intestine and select the one which is NOT correct :

• (A) The length of the small intestine in animals differs as it depends on the type of food they eat.
• (B) The small intestine is the site of complete digestion of food.
• (C) The small intestine receives secretions from liver and pancreas.
• (D) The villi of the small intestine absorb water from the unabsorbed food before it gets removed from the body via the anus. ✓

Answer (the board’s key): (D)

The statement that correctly describes the characteristic(s) of a gene is :

• (A) In individuals of a given species, a specific gene is located on a particular chromosome. ✓
• (B) A gene is not the information source for making proteins in the cell.
• (C) Each chromosome has only one gene located all along its length.
• (D) All the inherited traits in human beings are not controlled by genes.

Answer (the board’s key): (A)

Select from the following the correct statement about tropic movement in plants :

• (A) It is due to stimulus of touch and temperature.
• (B) It does not depend upon the direction of stimulus received.
• (C) It is observed only in roots and not in stems.
• (D) It is a growth related movement. ✓

Answer (the board’s key): (D)

Select the INCORRECT match (between the plant and its vegetative part) from the following :

• (A) Bryophyllum, leaf
• (B) Potato, stem
• (C) Money-plant, stem
• (D) Rose, root ✓

Answer (the board’s key): (D)

If four identical resistors, of resistance 8 ohm, are first connected in series so as to give an effective resistance Rs, and then connected in parallel so as to give an effective resistance Rp, then the ratio Rs/Rp is

• (A) 32
• (B) 2
• (C) 0.5
• (D) 16 ✓

Answer (the board’s key): (D)

In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have

• (A) higher power ratings such as geyser. ✓
• (B) lower power ratings such as fan.
• (C) metallic bodies and low power ratings.
• (D) non-metallic bodies and low power ratings.

Answer (the board’s key): (A)

In the following diagram, the position of the needle is shown on the scale of a voltmeter. The least count of the voltmeter and the reading shown by it respectively are :

• (A) 0.15 V and 1.6 V
• (B) 0.05 V and 1.6 V
• (C) 0.15 V and 1.8 V ✓
• (D) 0.05 V and 1.8 V

Answer (the board’s key): (C)

The resultant magnetic field at point 'P' situated midway between two parallel wires (placed horizontally) each carrying a steady current I is

• (A) in the same direction as the current in the wires.
• (B) in the vertically upward direction.
• (C) zero ✓
• (D) in the vertically downward direction.

Answer (the board’s key): (C)

Assertion (A) : The colour of aqueous solution of copper sulphate turns colourless when a piece of lead is added to it. Reason (R) : Lead is more reactive than copper, and hence displaces copper from its salt solution.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). ✓
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false.
• (D) Assertion (A) is false, but Reason (R) is true.

Answer (the board’s key): (A)

Assertion (A) : Genes inherited from the parents decide the sex of a child. Reason (R) : X chromosome in a male child is inherited from his father.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false. ✓
• (D) Assertion (A) is false, but Reason (R) is true.

Answer (the board’s key): (C)

Assertion (A) : Blood clotting prevents excessive loss of blood. Reason (R) : Blood clotting is due to blood plasma and white blood cells present in the blood.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false. ✓
• (D) Assertion (A) is false, but Reason (R) is true.

Answer (the board’s key): (C)

Assertion (A) : The strength of the magnetic field produced at the centre of a current carrying circular coil increases on increasing the number of turns in it. Reason (R) : The current in each circular turn has the same direction and the magnetic field due to each turn then just adds up.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). ✓
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false.
• (D) Assertion (A) is false, but Reason (R) is true.

Answer (the board’s key): (A)

21. (a) (i) A compound 'X' which is prepared from gypsum has the property of hardening when mixed with proper quantity of water. Identify 'X' and write its chemical formula. (ii) State the difference in chemical composition between baking soda and baking powder. OR (b) Write balanced chemical equation for the reaction that occurs when : (i) blue coloured copper sulphate crystals are heated and (ii) Sodium hydrogen carbonate is heated during cooking.

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(a) Write the role of insulin in the regulation of blood sugar level in the human body. Mention the disease caused by its deficiency. (b) How is the timing and amount of insulin released in the blood regulated?

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23. (a) Name the type of blood (oxygenated / deoxygenated) transported by each of the following mentioning the path (i.e. from one organ (which place) to another (which place)). (i) Vena cava (ii) Pulmonary artery OR (b) With the help of a schematic flow chart, show the breakdown of glucose in a cell to provide energy - (i) in the presence of oxygen (ii) in lack of oxygen

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24. Name the part of the human excretory system where nephrons are found. Write the structure and function of nephrons.

25. (a) A narrow beam XY of white light is passing through a glass prism ABC as shown in the diagram : Trace it on your answer sheet and show the path of the emergent beam as observed on the screen PQ. Name the phenomenon observed and state its cause. OR (b) It is observed that the power of an eye to see nearby objects as well as far off objects diminishes with age. (i) Give reason for the above statement. (ii) Name the defect that is likely to arise in the eyes in such a condition. (iii) Draw a labelled ray diagram to show the type of corrective lens used for restoring the vision of such an eye.

26. How do harmful chemicals get accumulated progressively at each trophic level in a food chain ?

(a) Identify the reducing agent in the following reactions : (i) 4NH_3 + 5O_2 -> 4NO + 6H_2O (ii) H_2O + F_2 -> HF + HOF (iii) Fe_2O_3 + 3CO -> 2Fe + 3CO_2 (iv) 2H_2 + O_2 -> 2H_2O (b) Define a redox reaction in terms of gain or loss of oxygen.

(a) Suggest one remedial measure each to counteract the change in pH in human beings in following cases : (i) Production of too much acid in stomach during indigestion (ii) Stung by a honey bee / nettle leaves (b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease ? Why ?

(a) (i) State the role of ATP in cellular respiration. (ii) What ensures sufficient exchange of gases in plants ? (iii) State the conditions on which the direction of diffusion of gases in plant depend upon. OR (b) (i) What is the internal energy reserve in plants and animals ? (ii) How desert plants perform photosynthesis if their stomata remain closed during the day ?

(a) Complete the following ray diagram to show the formation of image : (b) Mention the nature, position and size of the image formed in this case. (c) State the sign of the image distance in this case using the Cartesian sign convention.

Give reasons for the following : (a) Danger signals installed at airports and at the top of tall buildings are of red colour. (b) The sky appears dark to the passengers flying at very high altitudes. (c) The path of a beam of light passing through a colloidal solution is visible.

(a) (i) State the rule to determine the direction of force on a current carrying conductor in a magnetic field. (ii) Below are given cases in which an electron enters a magnetic field. Identify the case in which the force on the electron will be (1) maximum and (2) minimum. Give reason for your answers. OR (b) (i) Draw the pattern of magnetic field lines in the following cases : (1) Current carrying solenoid (2) Bar magnet (ii) List two distinguishing features between these two magnetic fields.

(a) (i) Why does a kitchen garden called an artificial ecosystem while a forest is considered to be a natural ecosystem ? (ii) While designing an artificial ecosystem at home, write any two things to be kept in mind to convert it into a self-sustaining system. Give reason to justify your answer. OR (b) (i) Construct a food chain of four trophic levels comprising the following : Hawk, snake, plants, rat. (ii) 20,000 J of energy was transferred by the producers to the organism of second trophic level. Calculate the amount of energy that will be transferred by organisms of the third trophic level to the organisms of the fourth trophic level.

(a) A saturated organic compound ‘A’ belongs to the homologous series of alcohols. On heating ‘A’ with concentrated sulphuric acid at 443 K, it forms an unsaturated compound ‘B’ with molecular mass 28 u. The compound ‘B’ on addition of one mole of hydrogen in the presence of Nickel, changes to a saturated hydrocarbon ‘C’. (i) Identify A, B and C. (ii) Write the chemical equations showing the conversion of A into B. (iii) What happens when compound C undergoes combustion ? (iv) State one industrial application of hydrogenation reaction. (v) Name the products formed when compound A reacts with sodium. OR (b) (i) With the help of diagram, show the formation of micelles, when soap is applied on oily dirt. (ii) Take two test tubes X and Y with 10 mL of hard water in each. In test tube ‘X’, add few drops of soap solution and in test tube ‘Y’ add a few drops of detergent solution. Shake both the test tubes for the same period. (1) In which test tube the formation of foam will be more ? Why ? (2) In which test tube is a curdy solid formed ? Why ?

(a) Name the parts of a bisexual flower that are not directly involved in reproduction. (b) Differentiate between self pollination and cross pollination. List any two significance of pollination. (c) What is the fate of ovules and ovary after fertilization in a flower ?

(a) An electric iron consumes energy at a rate of 880 W when heating is at the maximum rate and 330 W when the heating is at the minimum. If the source voltage is 220 V, calculate the current and resistance in each case. (b) What is heating effect of electric current ? (c) Find an expression for the amount of heat produced when a current passes through a resistor for some time.

Almost all metals combine with oxygen to form metal oxides. Metal oxides are generally basic in nature. But some metal oxides show both basic as well as acidic behaviour. Different metals show different reactivities towards oxygen. Some react vigorously while some do not react at all. (a) What happens when copper is heated in air ? (Give the equation of the reaction involved). (b) Why are some metal oxides categorized as amphoteric ? Give one example. (c) Complete the following equations : (i) Na2O(s) + H2O(l) -> (ii) Al2O3 + 2 NaOH ->

38. In order to trace the inheritance of traits Mendel crossed pea plants having one contrasting character or a pair of contrasting characters. When he crossed pea plants having round and yellow seeds with pea plants having wrinkled and green seeds, he observed that no plants with wrinkled and green seeds were obtained in the F1 generation. When the F1 generation pea plants were cross-bred by self-pollination, the F2 generation had seeds with different combinations of shape and colour also. (a) Write any two pairs of contrasting characteristics of pea plant used by Mendel other than those mentioned above. (1) (b) Differentiate between dominant and recessive traits. (1) (c) State the ratio of the combinations observed in the seeds of F2 generation (in the above case). What do you interpret from this result? (2) OR (c) Given below is a cross between a pure violet flowered pea plant (V) and a pure white flowered pea plant (v). Diagrammatically explain what type of progeny is obtained in F1 generation and F2 generation : Pure violet flowered plant x Pure white flowered plant (V V) (v v) (2)

39. Hold a concave mirror in your hand and direct its reflecting surface towards the sun. Direct the light reflected by the mirror on to a white card-board held close to the mirror. Move the card-board back and forth gradually until you find a bright, sharp spot of light on the board. This spot of light is the image of the sun on the sheet of paper; which is also termed as "Principal Focus" of the concave mirror. (a) List two applications of concave mirror. (1) (b) If the distance between the mirror and the principal focus is 15 cm, find the radius of curvature of the mirror. (1) (c) Draw a ray diagram to show the type of image formed when an object is placed between pole and focus of a concave mirror. (2) OR (c) An object 10 cm in size is placed at 100 cm in front of a concave mirror. If its image is formed at the same point where the object is located, find : (i) focal length of the mirror, and (2) (ii) magnification of the image formed with sign as per Cartesian sign convention.