CBSE Class 10 Science Theory (Code- 086) Term 1 Answer key 2021-22 available for Students. Complete Science Question Paper with Expert Share Answers.

SCIENCE (Theory) Subject code 086

Term-I

Objective Questions and Answers 

SECTION A

1 A student while burning a magnesium ribbon in the air, collected the products in a wet watch glass. The new product obtained was:

(a) Magnesium oxide

(b) Magnesium carbonate

(c) Magnesium hydroxide

(d) Magnesium chloride

 

2 Consider the following chemical equation:

2NaOH + H2SO4        Na2SO4 + 2H2O

The informations conveyed by this equation are:

 

1NaOH reacts with H2SO4 to produce Na2SO4 and water.

2 For every one molecule of H2SO4, two molecules of NaOH are required.

3 Acids and bases are non-ionic in nature.

4 This is not a redox reaction.

The correct statements are:

(a) I and II

(b) II and III

(c) III and IV

(d) I and IV

 

 

3 Select the correct matching in the following table in connection with the given chemical reaction:

CuSO4 + Fe        FeSO4 +Cu

 

Initial colour of solution	Final colour of solution	Final colour of iron nail	Type of reaction
(A) Pale green	Blue	Grey	Displacement
(B) Blue	Pale green	Brownish	Double displacement
(C) Blue	Light Blue	Grey	Double Displacement
(D) Blue	Pale Green	Brownish	Displacement

 

4 Consider the following processes:

I. Dilution of sulphuric acid

II. Sublimation of dry ice

III. Condensation of water vapours   

IV. Dissolution of ammonium chloride in water

 

The endothermic process(es) is/are :

(a) I and III     

(b) II only     

(c) III only     

(d) II and IV

 

 

5 A solution gives yellowish orange colour when a few drops of universal indicator are added to it. This solution is of :

(a) Lemon juice

(b) Sodium chloride

(c) Sodium hydroxide

(d) Milk of magnesia

 

6 Concentrated H2SO4 is diluted by adding drop by drop :

(a) Water to acid with constant stirring     

(b) Acid to water with constant stirring

(c) Water to acid followed by a base

(d) Base to acid followed by cold water

 

7 Absence of tartaric acid in baking powder makes the taste of the cake bitter due to the presence of :

(a) Sodium hydrogen carbonate

 (b) Sodium carbonate

(c) Sodium metabisulphite

(d) Sodium sulphate

 

8 The pH of acid rain is approximately :

(a) 5.6

(b) 6.4

(c) 7.0

(d) 7.9

 

9 Salt ‘A’ commonly used in food products, is a reactant to produce salt ‘B’, used in the kitchen for making tasty, crispy pakoras. Salt ‘B’ on heating converts into another salt ‘C’, which is used in the manufacturing of glass. Salts ‘A’, ‘B’ and ‘C’ respectively are :

(a) NaHCO3, NaCl, Na2CO3

(b) Na2CO3, NaHCO3, NaCl

(c) Na2CO3, NaCl, NaHCO3

(d) NaCl, NaHCO3, Na2CO3

 

 

10 In the following diagram, what would happen if some amount of sodium hydroxide is taken in place of sulphuric acid and the test tube is heated :

(a) Same amount of H2 gas is evolved

(b) H2 gas is not evolved

(c) The amount of H2 gas evolved is much less

(d) In place of H2 gas, O2 gas evolves

 

 

11 In Human Alimentary canal, the specific enzyme/juice secreted in locations (i), (ii) and (iii) are :

(a) (i) Amylase   (ii) Pepsin   (iii) Bile

(b) (i) Amylase   (ii) Bile   (iii) Trypsin

(c) (i) Lipase   (ii) Amylase   (iii) Pepsin

(d) (i) Trypsin   (ii) Bile   (iii) Amylase

 

12 The sequence of anaerobic respiration in our muscle cells during heavy exercise is :

(a) Glucose -> Cytoplasm Pyruvate ->Muscle cells Lactic acid + Energy

(b) Glucose ->Mitochondria Pyruvate ->Muscle cells Carbon dioxide + Water

(c) Glucose ->Cytoplasm Pyruvate->Muscle cells Ethanol + Carbon dioxide

(d) Glucose ->Mitochondria Pyruvate ->Muscle cells Ethanol + Lactic acid

 

13 The separation of the right side and the left side of human heart is useful to :

(a) Keep oxygenated blood from mixing with deoxygenated blood

(b) Allow a slow supply of oxygen in the body

(c) Supply energy to animals with low energy needs

(d) Often change their body temperature

 

14 In spring, sugar stored in root or stem tissue of plants is transported to the buds for :

(a) The energy needs of the buds to grow

(b) Temperature regulation

(c) Balancing the storage in different organs

(d) Diffusion process

 

15 The energy released during cellular respiration is used to synthesize :

(a) Ribosomes

(b) RBC

(c) ATP

(d) Mitochondria

16 Upward movement of water in tall trees is due to :

(a) Translocation

(b) Excretion

(c) Photosynthesis

(d) Transpiration

 

 

17 If a lens and a spherical mirror both have a focal length of – 15 cm, then it may be concluded that :

(a) Both are concave

(b) The lens is concave and the mirror is convex

(c) The lens is convex and the mirror is concave

(d) Both are convex

 

18 An optical device forms an erect image of an object placed in front of it. If the size of the image is one half that of the object, the optical device is a :

(a) Concave mirror

(b) Convex mirror

(c) Plane mirror

(d) Convex lens

19 A student determines the focal length of a device ‘A’ by focussing the image of a far off object on a screen placed on the opposite side of the object. The device ‘A’ is :

(a) Concave lens

(b) Concave mirror

(c) Convex lens

(d) Convex mirror

 

20 When light is incident on a glass slab, the incident ray, refracted ray and the emergent ray are in three media A, B and C. If n1, n2 and n3 are the refractive indices of A, B and C respectively and the emergent ray is parallel to the incident ray, which of the following is true ?

(a) n1 < n2 <n3

(b) n1 < n2 < n3

(c) n1 <  n2 = n3

(d) n1 = n3 <  n2

 

21 The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. According to new cartesian sign convention, if the image is three times the size of the flame, then the lens is :

(a) Concave and magnification is + 3

(b) Concave and magnification is – 3

(c) Convex and magnification is – 3

(d) Convex and magnification is + 3

 

22 The power of a combination of two lenses in contact is + 1.0 D. If the focal length of one of the lenses of the combination is + 20.0 cm, the focal length of the other lens would be :

(a) – 120.0 cm

(b) + 80.0 cm

(c) – 25.0 cm

(d) – 20.0 cm

23 When a ray of light passes through a glass prism it suffers two refractions. During these refractions the ray bends :

(a) Away from the base in both cases

(b) Towards the base in both cases

(c) Towards the base in first case and away from the base in second case

(d) Away from the base in first case and towards the base in second case

 

24 To an astronaut the sky on the moon appears dark because:

(a) There is no light on the moon

(b) There is no atmosphere on the surface of the moon

(c) Moon is a non-luminous object

(d) The surface of the moon absorbs all the sunlight

SECTION B

Section B consists of 24 questions. Attempt any 20 questions from this section. The first attempted 20 questions would be evaluated.

 

25 When lead nitrate powder is heated in a boiling tube, we observe :

(a) Brown fumes of nitrogen dioxide

(b) Brown fumes of lead oxide

(c) Yellow fumes of nitrogen dioxide

(d) Brown fumes of nitric oxide

 

26 An aqueous solution of a salt shows an orange red colour when a drop of universal indicator is added to it. This salt is made up of :

(a) A strong acid and a strong base

(b) A weak acid and a weak base

(c) A strong acid and a weak base

(d) A weak acid and a strong base

 

 

27 Three test tubes A, B and C contain distilled water, an acidic solution and a basic solution respectively. When red litmus solution is used for testing these solutions, the observed colour changes respectively will be :

(a) A – no change; B – becomes dark red; C – becomes blue

(b) A – becomes light red; B – becomes blue; C – becomes red

(c) A – becomes red; B – no change; C – becomes blue

(d) A – Becomes Light Red;  B – Becomes dar red;  C – Becomes blue

 

28 Given below is a reaction showing Chlor-alkali process :

2NaCl (aq) + 2H2O (l)               2NaOH (aq) + Cl2 (g) + H2 (g)

The products A, B, and C are produced respectively :

(a) At the anode, at the cathode, near the cathode

(b) Near the cathode, at the anode, at the cathode

(c) At the cathode, near the cathode, at the anode

(d) At the anode, near the cathode, at the cathode

 

 

29 In the activity shown in the diagram, if the climate is humid, the role of calcium chloride taken in the guard tube is to :

(a) Absorb the evolved gas

(b) Warm up the gas

(c) Dry the gas

(d) Absorb chloride ions from the evolved gas

 

30 Which one of the following chemicals is used in soda acid fire extinguishers ?

(a) Sodium chloride

(b) Sodium acetate

(c) Sodium hydrogen carbonate

(d) Ammonium sulphate

 

 

Questions No. 31 to 34 consists of two statements — Assertion (A) and Reason (R). Answer these

questions selecting the appropriate options given below :

 

(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.

 

31 Assertion (A) : Silver salts are used in black and white photography.

Reason (R) : Silver salts do not decompose in the presence of light.

Answer:-  C

32 Assertion (A) : The solutions of ionic compounds are good conductors of electricity.

Reason (R) : Movement of atoms of elements take place in solution.

Answer:-  C

 

33 Assertion (A) : The rate of breathing in aquatic organisms is much slower than that seen in terrestrial organisms.

Reason (R) : The amount of oxygen dissolved in water is very low as compared to the amount of oxygen in air.

Answer:-  D

 

 

34 Assertion (A) : Kerosene having higher refractive index is optically denser than water, although its mass density is less than that of water.

Reason (R) : The speed of light decides whether a medium is optically rarer or optically denser. An optically denser medium may not possess greater mass density.

Answer:-  B

 

 35 Match the metal (Column I) with its reaction with oxygen (Column II) :

           Column I                                                              Column II

1. Potassium                                 (i)            Does not react event at high temperatures
2. Zinc                                            (ii)           Gets coated with black-coloured layer of oxide
3. Copper                                       (iii)          Does not burn at ordinary temperature
4. Silver                                          (iv)          Burns vigorously

(a) A-(iv), B-(iii), C-(ii), D-(i)

(b) A-(iv), B-(ii), C-(i), D-(iii)

(c) A-(iii), B-(ii), C-(i), D-(iv)

(d) A-(iv), B-(ii), C-(iii), D-(I)

 

36 Four test tubes A, B, C and D are taken. In test tube A iron nail is dipped in copper sulphate solution. In test tube B copper wire is dipped in ferrous sulphate solution. In test tube C zinc metal is dipped in ferrous sulphate solution and in test tube D iron nail is dipped in zinc sulphate solution. The reactivity order has been found to be Zn > Fe > Cu. In which test tubes was the colour change observed ?

(a) A and C

(b) A and B

(c) B and C

(d) B and D

 

37 The function not performed by villi is :

(a) To increase the surface area for absorption

(b) To ensure rich supply of blood vessels

(c) Absorption of food

(d) Egestion of food

38 In the given diagram, A, B, C and D respectively are :

(a) A – Left kidney; B – Aorta; C – Vena cava; D – Urethra

(b) A – Left kidney; B – Vena cava; C – Aorta; D – Urinary bladder

(c) A – Right kidney; B – Aorta; C – Ureter; D – Urethra

(d) A – Right kidney; – Vena cava; C – Aorta; D – Urinary bladder

 

 

39 Thin walled blood vessels are called :

(a) Aorta

(b) Capillaries

(c) Arteries

(d) Vena cava

 

40 The function of the lining of mucus in the nasal passage of human beings is to :

(a) Increase the temperature of inhaled air

(b) Move the air in and out

(c) Filter the air that we breathe in

(d) Absorb oxygen from the air

 

41 In the following flow chart showing autotrophic nutrition in green plants, A and Brespectively are :

(a) Oxygen and energy

(b) Starch and oxygen

(c) Energy and starch

(d) Oxygen and water

 

42 Study the diagram given below and identify the type of the lens XX and the position of the point on the principal axis Oó where the image of the object AB appears to be formed:

(a) Concave; between ó and Y

(b) Concave; between O and Y

(c) Convex; between ó and Y

(d) Convex; between O and Y

43 The image of an object placed in front of a concave mirror of focal length 15 cm is of the same size as the object. The distance between the object and its image is :

(a) 15 cm

(b) 30 cm 

(c) 60 cm

(d) Zero

44 An object of height 3.0 cm is placed vertically on the principal axis of a convex lens. When the object distance is – 37.5 cm, an image of height – 2.0 cm is formed at a distance of 25.0 cm from the lens. Next, the same object is placed vertically at 25.0 cm from the lens. In this situation the image distance v and height h of the image is (according to the new Cartesian sign convention) :

(a) v = + 37.5 cm; h = + 4.5 cm

(b) v = – 37.5 cm; h = + 4.5 cm

(c) v = + 37.5 cm; h = – 4.5 cm

(d) v = – 37.5 cm; h = – 4.5 cm

45 The relation R = 2f is valid :

(a) For concave mirrors but not for convex mirrors

(b) For convex mirrors but not for concave mirrors

(c) Neither for concave mirrors nor for convex mirrors

(d) For both concave and convex mirrors

 

46 A lens has a power of + 4.0 D. It is :

(a) A convex lens of focal length 4 m

(b) A concave lens of focal length 4 m

(c) A convex lens of focal length 0.25 m

(d) A concave lens of focal length 0.25 m

 

47 An object is placed in front of a concave lens. For all positions of the object the image formed is always :

(a) Real, diminished and inverted

(b) Virtual, diminished and erect

(c) Real, enlarged and erect

(d) Virtual, erect and enlarged

 

48 The twinkling of star is due to :

(a) Scattering of light

(b) Dispersion of light

(c) Tyndall effect

(d) Atmospheric refraction

SECTION C

Section C consists of three cases followed by questions. There are a total of 12 questions in this section. Attempt any 10 questions from this section. The first attempted 10 questions would be evaluated.

Case I

One day Kamal saw that her mother was roasting peanuts in a pan (kadahi) in the kitchen and she had taken ordinary salt to roast the peanuts. She was surprised to observe that in spite of very high temperature, the salt does not melt and the peanuts also get roasted.

 

49 The chemical name of common salt is :

(a) Potassium chloride

(b) Sodium carbonate

(c) Sodium hydrogen carbonate

(d) Sodium chloride

 

 

50 Common salt is :

(a) A covalent compound

(b) An ionic compound formed by sharing electrons

(c) An ionic compound formed by the transfer of electrons

(d) Soluble in organic solvents

 

51 Common salt is not a raw material for :

(a) Bleaching powder

(b) Plaster of Paris

(c) Baking soda

(d) Caustic soda

 

52 Common salt is used as a raw material in the preparation of washing soda in which the number of molecules of water of crystallisation is :

(a) 10

(b) 7

(c) 5

(d) 2

Case II

Activity: Take a healthy potted plant with elongated leaves. Select a leaf and insert about one half of this leaf in a test tube containing KOH and make it air tight. Place the set-up in sun for two hours. Take out the leaf from the test tube and dip it in boiling water for a few minutes. Put this leaf in a beaker with alcohol and boil it in a water bath. Wash the leaf with water and then dip the leaf in iodine solution for a few minutes. The portion of the leaf dipped in KOH solution will not show any change when dipped in iodine solution.

53 The function of KOH taken in the test tube is to absorb:

(a) Released water vapours

(b) Released CO2

(c) Released O2

(d) Chlorophyll

54 On the basis of this activity, we may conclude that the essential factor for photosynthesis is :

(a) Carbon dioxide

(b) Oxygen

(c) Chlorophyll

(d) Water vapour

55 The event that does not occur in photosynthesis is :

(a) Absorption of light energy by chlorophyll

(b) Reduction of carbon dioxide to carbohydrates

(c) Oxidation of carbon to carbon dioxide

(d) Conversion of light energy to chemical energy

 

56 Iodine solution gives blue-black colour with :

(a) Starch

(b) Proteins

(c) Glucose

(d) Fats

Case-III

On a sunny day, Krish looked at the sky through a water fountain and was surprised to see a rainbow in the sky.

57 The location of the sun when Krish observed a rainbow was:

(a) Behind him

(b) In front of him

(c) Overhead

(d) On his left side

58 The phenomena of light involved in the formation of a rainbow are :

(a) Reflection, refraction, dispersion

(b) Refraction, dispersion, internal reflection

(c) Refraction, dispersion, scattering

(d) Dispersion, scattering, internal reflection

 

59 In the formation of a rainbow, the role of water droplets present in the water fountain is to act as a :

(a) Glass slab

(b) Convex lens

(c) Concave lens

(d) Prism

60 While entering a water droplet the sunlight gets :

(a) Refracted only

(b) Reflected internally

(c) Refracted and dispersed

(d) First refracted and then dispersed while coming out of the water droplet