Class X - Science - 2023 - Paper 5 - Practice for Everyone

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Q.P Code: 31/1/1

Science

Time allowed: 3 hours Maximum Marks: 80

● Please check that this question paper contains 31 printed pages.

● Q.P. Code number given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate.

● Please check that this question paper contains 39 questions.

● Please write down the Serial Number of the question in the answer book before attempting it.

● 15 minutes’ time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the candidates will read the question paper only and will not write any answer on the answer-book during this period

General Instructions:

Read the instructions very carefully and strictly follow them:

(i) This question paper consists of 39 questions. All questions are compulsory.

(ii) Question paper is divided into FIVE sections viz. Section A, B, C, D and E

In Section – A – question number 1 to 20 are Multiple Choice Questions (MCQs) carrying 1 mark each.

In Section – B question number 21 to 26 are Very Short Answer (VSA) type questions carrying 2 marks each. Answer to these questions should be in the range of 30 to 50 words.

In Section – C – question number 27 to 33 are Short Answer (SA) type questions carrying 3 marks each. Answer to these questions should be in the range of 50 to 80 words

In Section – D – question number 34 to 36 are Long Answer (LA) type questions carrying 5 marks each. Answer to these questions should be in the range of 80 to 120 words.

In Section – E – question number 37 to 39 are of 3 source-based/case –based units of assessment carrying 4 marks each with sub-parts.

There is no overall choice. However, an internal choice has been provided in some Sections.

(iii) Attempt questions based on specific instructions for each Part.

Section – A

Select and write one most appropriate option out of the four options given for each of the questions 1 – 20:

1. In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the solution ‘X’ the solution ‘X’ first turns milky and then colourless.

The option that justifies the above stated observation is that ‘X’ is aqueous calcium hydroxide and

(a) it turns milky due to carbon dioxide gas liberated in the reaction and after sometime it becomes colourless due to formation of calcium carbonate.

(b) it turns milky due to formation of calcium carbonate and on passing excess of carbon dioxide it becomes colourless due to formation of calcium hydrogen carbonate which is soluble in water.

(c) it turns milky due to passing of carbon dioxide through it. It turns colourless as on further passing carbon dioxide, sodium hydrogen carbonate is formed which is soluble in water.

(d) the carbon dioxide liberated during the reaction turns lime water milky due to formation of calcium hydrogen carbonate and after some time it turns colourless due to formation of calcium carbonate which is soluble in water.

View Answer

Ans. (b) it turns milky due to formation of calcium carbonate and on passing excess of carbon dioxide it becomes colourless due to formation of calcium hydrogen carbonate which is soluble in water.

2. The emission of brown fumes in the given experimental setup 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.

(d) oxidation of lead nitrate forming lead oxide and oxygen.

View Answer

Ans. (a) thermal decomposition of lead nitrate which produces brown fumes of nitrogen dioxide.

3. MnO₂ + x HCl → MnCl₂ + y H₂O + z Cl₂

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

(d) 2, 2, 1

View Answer

Ans. (c) 4, 2, 1

4. The table below has information regarding pH and the nature (acidic/basic) of four different solutions. Which one of the options in the table is correct?

View Answer

Ans. Option (b)

5. 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 Fe₂O₃

(b) Al and Al₂O₃

(d) Al and Al₃O₄

View Answer

Ans. (b) Al and Al₂O₃

6. Select washing soda from the following:

(a) NaHCO₃

(b) Na₂CO₃.5H₂O

(d) NaOH

View Answer

Ans. (c) Na₂CO₃.10H₂O

7. 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.

(d) A is cyclohexane and B and C are the isomers of benzene.

View Answer

Ans. (c) A is a saturated cyclic hydrocarbon and B and C are unsaturated cyclic hydrocarbons.

8. 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

(d) a fun, Rhizopus

View Answer

Ans. (d) a fun, Rhizopus

9. 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.

(d) villi of the small intestine absorb water from the unabsorbed food before it gets removed from the body via the anus.

View Answer

Ans. (d) villi of the small intestine absorb water from the unabsorbed food before it gets removed from the body via the anus.

10. 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.

(d) All the inherited traits in human beings are not controlled by genes.

View Answer

Ans. (a) In individuals of a given species, a specific gene is located on a particular chromosome.

11. 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.

(d) It is a growth related movement.

View Answer

Ans. (d) It is a growth related movement.

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

(a) Bryophyllum, leaf

(b) Potato, stem

(d) Rose, root

View Answer

Ans. (d) Rose, root

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

(a) 32

(b) 2

(d) 16

View Answer

Ans. (d) 16

14. 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.

(d) non-metallic bodies and low power ratings.

View Answer

Ans. (a) higher power ratings such as geyser.

15. 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) 0.15V and 1.6V

(b) 0.05V and 1.6V

(d) 0.05V and 1.8V

View Answer

Ans. (c) 0.15V and 1.8V

16. 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

(d) in the vertically downward direction.

View Answer

Ans. (c) zero

These consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

(a) Both (A) and (R) are true and (R) is the correct explanation of (A)

(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A)

(d) (A) is false, but (R) is true

17. Assertion (A): the colour of aqueous of copper sulphate turns colourless when a piece of lead is added to it.

Reason (R) : Lead is more reactive than copper, hence displaces copper from its salt solution.

View Answer

Ans. (a) Both (A) and (R) are true and (R) is the correct explanation of (A)

18. 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.

View Answer

Ans. (c) (A) is true, but (R) is false

19. 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.

View Answer

Ans. (c) (A) is true, but (R) is false

20. 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.

View Answer

Ans. (a) Both (A) and (R) are true and (R) is the correct explanation of (A)

SECTION – B

Q. No 21 to 26 are very short answer questions

21. (a) (i) A compound X which is prepared from gypsum has the property of hardening when mixed with proper quantity of water. 2

Identify ‘X’ and write its chemical formula.

View Answer

Ans. X: Plaster of Paris/Calcium sulphate hemihydrate.

CaSO₄.1/2H₂O

(ii) State the difference in chemical composition between baking soda and baking powder.

View Answer

Ans. • Baking Soda – NaHCO₃ /Sodium hydrogen carbonate/Sodium bicarbonate

• Baking Powder – A mixture of NaHCO₃ /Baking soda + Tartaric acid/any mild edible acid

(b) Write balanced chemical equation for the reaction that occurs when : 2

(i) blue coloured copper sulphate crystals are heated and

View Answer

Ans.

(ii) Sodium hydrogen carbonate is heated during cooking.

View Answer

Ans.

22. (a) Write the role of insulin in regulating blood sugar levels in human body. Mention the disease caused due to it. 2

View Answer

Ans. • Lowers blood sugar levels

• Diabetes

(b) How is the timing and the amount of release of insulin in the blood regulated?

View Answer

Ans. The rise in sugar level in blood produces more insulin. As the blood sugar level falls, secretion is reduced.

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)). 2

(i) Vena cava

View Answer

Ans. deoxygenated blood from body to heart.

(ii) Pulmonary artery

View Answer

Ans. deoxygenated blood from heart to lungs.

(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

View Answer

Ans.

(ii) in lack of oxygen

View Answer

Ans.

25 (a) A narrow beam XY of white light is passing through a glass prism. ABC as shown in the diagram: 2

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.

View Answer

Ans.

• Dispersion of white light

• Cause: Different colours of light bend through different angles w.r.t. the incident ray. / Different colours have different wavelengths.

(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.

View Answer

Ans. It is due to gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens.

(ii) Name the defect that is likely to arise in the eyes in such a condition.

View Answer

Ans. Presbyopia/ Presbyopia + Myopia

(iii) Draw a labelled ray diagram to show the type of corrective lens used for restoring the vision of such an eye.

View Answer

Ans. Bifocal /Concave + Convex lens/ Diagram

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

View Answer

Ans. The chemicals sprayed on crops are washed down into the soil. From the soil these are absorbed by plants along with water and minerals, plants are eaten by animals. This way they enter in a food chain. As these chemicals are not degradable, these get accumulated progressively at each successive trophic level. This phenomenon is called bio magnification.

SECTION – C

Q. No 27 to 33 are short answer questions.

27. (a) Identify the reducing agent in the following reactions :

(i) 4NH₃ +50₂ → 4NO + 6H₂O

View Answer

Ans. NH₃

(ii) H₂O+F₂ → HF + HOF

View Answer

Ans. H₂O

(iii) Fe₂O₃+3C0 → 2Fe + 3CO₂

View Answer

Ans. CO

(iv) 2H₂ + O₂ → 2H₂O

View Answer

Ans. H₂

(b) Define a redox reaction in terms of gain or loss of oxygen.

Ans. A reaction in which the gain or loss of oxygen takes place simultaneously is called a redox reaction.

28. (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

View Answer

Ans. Use of antacids

(ii) Stung by a honey bee / nettle leaves

View Answer

Ans. Baking soda/mild base/dock plant.

(b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease? Why?

View Answer

Ans. pH will decrease, as curd is more acidic than milk.

29. (a) (i) State the role of ATP in cellular respiration.

View Answer

Ans. Energy currency for cellular processes / ATP breaks down to give a fixed amount of energy which can drive the endothermic reactions taking place in the cell.

(ii) What ensures sufficient exchange of gases in plants?

View Answer

Ans. Stomata and surface of leaves, stems and roots.

(iii) State the conditions on which the direction of diffusion of gases in plant depend upon.

View Answer

Ans. Environmental conditions

Requirements of the plant.

(b) (i) What is the internal energy reserve in plants and animals?

View Answer

Ans. Plants -Starch

Animals- Glycogen

(ii) How desert plants perform photosynthesis if their stomata remain closed during the day?

View Answer

Ans. Desert plants take up carbon dioxide at night and prepare an intermediate compound which is acted upon by the energy absorbed by the chlorophyll during the day.

30. (a) Complete the following ray diagram to show the formation of image:

View Answer

Ans.

A’ B’ is the image formed.

(b) Mention the nature, position and size of the image formed in this case.

View Answer

Ans. Nature: Virtual and erect

Position: Behind the mirror (between P and F)

Size: Diminished

View Answer

Ans. Positive

31. Give reasons for the following:

(a) Danger signals installed at airports and at the top of tall buildings are of red colour.

View Answer

Ans. Red Coloured light is least scattered by fog or smoke and can be easily seen from a distance. / Red colour has high wavelength thus scattering is less.

(b) The sky appears dark to the passengers flying at very high altitudes.

View Answer

Ans. There is no scattering of light due to lack of atmosphere.

View Answer

Ans. Particles of colloid are big enough to scatter the beam of light.

32. (a) (i) State the rule used to find the force acting on a current carrying conductor placed in a magnetic field.

View Answer

Ans. Flemings left-hand rule:

Stretch the forefinger, the central finger and the thumb of your left hand in mutually perpendicular directions. If the forefinger shows the direction of the magnetic field and the central finger that of the current, then the thumb will point towards the direction of motion of the conductor or direction of force

(ii) Given below are three diagrams showing entry of an electron in a magnetic field. Identify the case in which the force will be (1) maximum and (2) minimum respectively. Give reason for your answer.

View Answer

Ans. (1) Force on electron is maximum in Fig (i) because the direction of motion of electron/current is at right angle/perpendicular to that of magnetic field.

(2) Force on electron is minimum in Fig (iii) because the electron is moving along / parallel to the direction of magnetic field

(b) (i) Draw the pattern of magnetic field lines of

(1) a current carrying solenoid

(2) a bar magnet

View Answer

Ans. (1)

(2)

(ii) List two distinguishing features between the two fields.

View Answer

Ans.

33. (a) (i) Why does a kitchen garden called an artificial ecosystem while a forest is considered to be a natural ecosystem?

View Answer

Ans. Kitchen Garden → A man made ecosystem /non-sustainable

Forest → Ecosystem maintained by nature / self-sustainable

(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.

View Answer

Ans. In a jar containing water we can provide oxygen through a pump and add a few aquatic plants and animals to make it a self-sustaining system.

Justification –

• Oxygen is replenished continuously.

• Aquatic plants serve as food.

(b) (i) Construct a food chain of four trophic levels comprising the following:

Hawk, snake, plants, rat

View Answer

Ans. Plants ⎯→ Rats⎯→ Snakes ⎯→ Hawks

(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.

View Answer

Ans. Energy available at second trophic level = 20,000 J

Energy transferred from second to third trophic level = 2000 J

Energy transferred from third to fourth trophic level = 200 J

SECTION – D

Q. No 34 to 36 are long answer questions.

34. (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.

View Answer

Ans. A: CH₃CH₂OH / Ethanol / Ethyl alcohol

B: CH₂ = CH₂ / Ethene

C: CH₃ – CH₃ / Ethane

(ii) Write the chemical equations showing the conversion of A into B.

View Answer

Ans.

(iii) What happens when compound C undergoes combustion?

View Answer

Ans. Carbon dioxide and water are produced and a large amount of heat is released

C₂H₆ + O₂ → 2CO₂ + 3H₂O + Heat

(iv) State one industrial application of hydrogenation reaction.

View Answer

Ans. Conversion of vegetable oil into fats.

(v) Name the products formed when compound A reacts with sodium.

View Answer

Ans. Sodium ethoxide and hydrogen

(b) (i) With the help of diagram, show the formation of micelles, when soap is applied on oily dirt.

View Answer

Ans.

(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?

View Answer

Ans. Test tube ‘Y’.

• Detergents are effective in hard water.

(2) In which test tube is a curdy solid formed? Why?

View Answer

Ans. • Test tube ‘X’

• Reaction between soap and calcium and magnesium salts of hard water form insoluble scum / due to formation of scum / insoluble ppt.

35. (a) Name the parts of a bisexual flower that are not directly involved in reproduction.

View Answer

Ans. Sepals/calyx and petals/ corolla

(b) Differentiate between self-pollination and cross pollination. List any two significance of pollination.

View Answer

Ans. Self-pollination: Transfer of pollen grain from anther to stigma in the same flower or another flower of the same plant.

Cross pollination: Transfer of pollen grain from anther to stigma of one flower to another of two different plants.

• Significance.

1. Necessary for seed formation.

2. Stimulates development of fruits.

3. Cross pollination brings about genetic variation

4. Leads to fertilization

View Answer

Ans. Ovule – seed

Ovary – Fruit.

36. (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.

View Answer

Ans. When heating is at maximum rate.

Power, P = 880 W

Voltage, V = 220 V

Current, I = P/ V =880/220= 4A

Resistance, R = V/ I = 220/4= 55 ohm

When heating is at minimum rate

Power, P = 330W

Voltage, V = 220 V

Current, I = P/V = 330/220 = 3/2 =1.5A

Resistance, R = V/I =220/115 =146.6 ohm

(b) What is heating effect of electric current?

View Answer

Ans. When electric current is passed through a resistor, electrical energy is dissipated and appears as heat energy.

View Answer

Ans. H = I²Rt/

H=VIt

SECTION – E

Q. No. 37 to 39 are case based/data based questions with 2 to 3 short sub-parts. Internal choice is provided in one of these sub-parts.

37. 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 reactivity’s 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).

View Answer

Ans. 2Cu + O2 ⎯→ ⎯ 2CuO

(b) Why are some metal oxides categorized as amphoteric? Give one example.

View Answer

Ans. • Because they react with both acids and bases to produce salt and water.

• Al₂O₃/ ZnO

(i) Na₂O (s) + H₂O (l) — >

View Answer

Ans. 2NaOH (aq)

(ii) Al₂O₃ + 2NaOH — >

View Answer

Ans. 2NaAlO₂ + H₂O

(i) Write chemical equation for the reaction.

View Answer

Ans. 2NaAlO₂ + H₂O

(ii) Name the gas formed.

View Answer

Ans. Sulphur dioxide

(iii) State the nature of the gas.

View Answer

Ans. Acidic

(iv) What will be the action of this on a dry litmus paper?

View Answer

Ans. No change

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.

View Answer

Ans. Tall – Dwarf (Height of plant)

White – Purple (Colour of flower)

(b) Differentiate between dominant and recessive traits.

View Answer

Ans. Dominant Trait – are expressed even if one copy of dominant trait exists.

Recessive Trait – Whose expression is suppressed by a dominant gene/ Expressed when two copies of recessive traits are present.

(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?

View Answer

Ans. 9: 3: 3: 1

Interpretation: Traits are independently inherited.

(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)

View Answer

Ans.

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.

View Answer

Ans. Torches, search light, vehicles head lights, shaving mirrors, dentist’s mirror, Solar furnaces.

(b) If the distance between the mirror and the principal focus is 15 cm, find the radius of curvature of the mirror.

View Answer

Ans. f = 15cm

R = 2 f

R = 2 × 15 cm = 30 cm

(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.

View Answer

Ans.

(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

View Answer

Ans. h = + 10cm u = – 100 cm v = – 100 cm

1/v + 1/u = 1/f

-1/100 – 1/100 = 1/f

-2/100 = 1/f

F = -50 cm

(ii) magnification of the image formed with sign as per Cartesian sign convention.

View Answer

Ans. m=-v/u = -(-100)/100 = 1

Class X – Science – 2023 – Paper 5