Class 10 Science Board Exam Sample Questions and Answers

Class 10 Students can go through this as a ready reckoner for their Science Board Examination 

All answers are given in blue

 1. Fe + ZnSO₄ 

No reaction takes place as Iron is less reactive than Zinc

2. What happens when zinc granules is added to freshly prepared ferrous sulphate solution?

A greyish black coating is formed.

Zinc is more electropositive than iron and so it can displace iron from its solution.  The solution turns colourless from light green.

3. An aqueous solution A turns phenolphthalein solution pink.  On addition of an aqueous solution B to A, the pink colour disappears. What can you say about A and B?

A has pH greater than 7 and B has pH less than 7.

4. What happens when ethanol reacts with sodium?

Sodium ethoxide is formed 

5. What happens when ethanol reacts with potassium permanganate solution?

Ethanoic acid

6. Scientific term for studying the development of new types of organisms from the existing ones

Evolution 

7. Spherical mirror used as shaving mirror 

Concave mirror 

8. Spherical mirror used as rear view mirror in vehicles

Convex mirror 

9. Spherical mirror used as reflection in search light

Concave mirror 

10. Carbon forms largest number of compounds. Give two reasons.

Catenation: The property of an element to combine with itself ( covalent bonds) to form long chains or structures.

Tetravalency: Carbon has a valency of four. So, it is capable of bonding with four other atoms of itself or of some other elements.

11. List two observations on the basis of which it may be concluded that the given slide shows binary fission 

1. Nucleus elongated

2. Constriction in cytoplasm II membrane 

12. A metal that does not react with cold as well as hot water but reacts with steam.

Aluminium 

13. Name a metal that does not react with any physical state of water.

Copper 

14. Write two properties of gold which makes it the most suitable metal for ornaments.

Malleability and ductility 

15. Name two metals which are the best conductors of heat

Silver and Copper 

16. Predict the reaction 

Zinc and silver nitrate solution 

Zinc is more reactive than silver. So it will displace silver and form zinc nitrate.

17. Predict the reaction 

Magnesium and iron ( II ) chloride solution 

Magnesium is more reactive than iron. So it will displace iron and form magnesium chloride.

18. Predict the reaction 

Copper and magnesium sulphate solution 

Copper is less reactive than magnesium.  So it will not displace magnesium and hence no reaction will take place.

19. A lump of element X can be cut by a knife. During its reaction with water, X floats and melts. What is X? Explain 

X is potassium (K). Potassium is a soft metal and so it can be cut by a knife.

It is lighter than water and so it floats on the water surface and the heat produced melts the potassium.

20. Name two metals which melt when you keep them on your palm

Gallium and Caesium

21. Dominant trait

A trait which is able to express itself both in homozygous as well as heterozygous condition 

22. Recessive trait

A trait which expresses itself only in homozygous condition.

23. What causes the movement of food inside the alimentary canal?

Peristalsis

24. Why is the small intestine in herbivores longer than in carnivores?

Digestion of cellulose takes a longer time and hence herbivores need a longer small intestine for complete digestion of cellulose.

Carnivores cannot digest cellulose and hence have a shorter intestine.

25, What will happen if the mucus is not secreted by the gastric glands?

Lack of mucus will damage the inner lining of the stomach by acid activity and may result in gastric ulcers.

26. Why is nutrition necessary for the human body?

It supports normal growth, development, aging, promotes healthy pregnancy outcomes, helps to maintain healthy body weight and reduces the risk of disease leading to overall well-being of human beings.

27. What causes hardness of water ?

Magnesium and calcium salts.

Temporary hardness is caused by the presence of dissolved bicarbonate minerals - calcium bicarbonate and magnesium bicarbonate.

28. The metal with lowest density is ______

Lithium

29. Find the current flowing through the wire of resistance 2 connected to a source of 50 V at its two ends.

Zero, current flows due to potential difference and not due to potential.

30.  The total number of electrons shared in the formation of an ethyne molecule is ____

10 electrons

31. The process common to aerobic and anaerobic respiration is ________

Glycolysis

32. Father of human genetics is _______

Gregor Mendel

33. In a flower the parts that produce male and female gametes ( germ cells) is ________

Anther and ovary

34.  Alternative forms of a 

gene are called ______

Allele

35. The process of inducing a current in a coil of wire by placing it in a region of changing magnetic field is _____

Electromagnetic induction 

36. A system of inter dependent food chains represents __________

Food web

37. A non metal which conducts electricity ___

Carbon

38. A non metal having lustre _______

Iodine

39. List two main causes of a person developing near sightedness (myopia)

Excessive curvature of eye lens

Elongation of eyeball

40. List some non metals

Carbon, Sulphur, Phosphorous, Silicon, Oxygen

41. A refrigerator rated 400 W operates 8 hours a day.  What is the cost of the energy to operate it for 30 days at Rupees three per kWh.

Total energy consumed in 30 days = 400 x 8 x 30 = 96000 Wh = 96 kWh

Cost of energy = 96 x 3 = ₹. 288/-

42. A non metal which is extremely hard ________

Diamond

43.  What is likely to happen if green plants disappear from earth?

It will be a total disaster for the ecosystem. Concentration of oxygen will be too low and it will not be sufficient for all the living organisms to breathe,

Green plants are the sources of energy and all organisms depend on them for food.  So if they disappear from the earth, it will result in extinction of life on earth.

44, Give reasons

Sulphur is a non metal

1. It is a poor conductor of electricity

2, Neither malleable nor ductile

3. Forms acidic oxides

45. Give reasons

Magnesium is a metal 

1. Good conductor of electricity

2, Malleable and ductile

3, Forms basic oxides

46. Why do copper articles turn green when kept for long?

Corrosion

A metal is eaten up gradually by the action of air, moisture or a chemical on their surface.

47. Name the products formed when ethanol reacts with sodium

Sodium ethoxide and hydrogen

48. Aluminium is used for making cooking utensils. Why?

Good thermal conductivity and high melting point.

49. How many covalent bonds does ethane have _______

7 covalent bonds

50. Fertilization of ovum takes place in _____

Fallopian tubes

51. Name the component of a chromosome that controls heredity.

DNA

It is a molecule that encodes genetic information.

52. The blood leaving the tissues becomes richer in _________

Carbon dioxide

53. Give reason

The strength of an electromagnet after the limit cannot be increased by increasing the current through the solenoid.  

Because the current flowing through the solenoid is saturated.

54. A metal that does not corrode in moist air 

Gold

55. The egg of an animal contains 10 chromosomes of which one is X chromosome.  How many autosomes would be there in the karyotype of this animal?

18 autosomes 

56. Characters transmitted from parents to offspring are present in ________

Genes

57. Magnetic field inside a solenoid is 

Same at all points 

58. Elements of electric heating devices are made of _____

Nichrome 

59. Use of high temperature for waste disposal is called _____

Incineration ( usually more than 1000°C )

60. Two devices which work on the heating effect of electric current 

Electric heater and electric iron

61. Energy rich compound produced through respiration 

ATP

62. A product of meiosis 

Megaspore 

63. An alloy that contains non metal as one of its constituents

Steel  (An alloy of metal iron and non metal carbon)

64. Give reason 

The existence of decomposers is essential in a biosphere 

They return nutrients back to the environment by breaking down dead complex organic matter into recyclable simpler compounds 

65. Give reason

Flow of energy in a food chain is unidirectional 

Because the food chain progress, the energy always passes from lower trophic level to upper level only.

66. A metal that does not stick to glass 

Mercury 

67. Metal commonly used in thermite welding 

Aluminium 

68. Which gets deposited at the cathode - A pure metal or an impure metal?

Pure metal 

69. Nature of zinc oxide 

An amphoteric oxide 

70. A non metal that is a good conductor of electricity 

Graphite 

71. Give reason

Ionic compounds have high melting and boiling points

In the ionic compounds, the oppositely charged ions are held together by strong ionic bonds which require a lot of heat to break these bonds.

72. Give reason

Sodium is kept immersed in kerosene

Sodium is a highly reactive metal and it will instantly burn in air. So kerosene cuts off the contact of sodium with air.

73. Give reason

Reaction of calcium with water is less violent

The heat evolved in this reaction is insufficient to burn hydrogen gas evolved during the reaction.

74. Give reason

Carbon cannot reduce the oxide of  Na or Mg

Sodium and Magnesium have a tendency to react with oxygen than carbon because these are highly reactive metals. 

75. Iron articles are galvanised

To prevent them from rusting.  After galvanization, zinc works as a protective layer.

Note: Students, kindly refer your textbook in case of any doubt or clarification as regards to the questions and answers given above.