NCERT Class 10 Science Most Important Questions Answers For Board Examination 2025

1. Name a metal/non-metal

(a) Carbon makes iron hard and strong (used in steel alloys).
(b) Mercury is alloyed with other metals to form amalgam.
(c) Zinc is used to galvanize iron articles.
(d) Silver forms a black coating (silver sulfide) when exposed to air.

2. A metal (E) is stored under kerosene oil…

(a) The metal $E$ is Sodium (Na).
(b) Chemical reactions:

1. $$4Na+O2→2Na2O4Na + O_2 → 2Na_2O
2. $Na_2O + H_2O → 2NaOH$ (turns red litmus blue due to its basic nature).
   (c) Process of extraction: Sodium is obtained through electrolysis of molten sodium chloride. Sodium ions move to the cathode, gaining electrons to form sodium metal.

3. Give reasons

(a) Carbonate and sulfide ores are converted to oxides as oxides are easier to reduce to metals.
(b) Ionic compounds have high melting points due to the strong electrostatic forces between oppositely charged ions.
(c) Hydrogen is placed in the reactivity series as it helps compare the reactivity of metals by their tendency to displace hydrogen from acids.
(d) Zinc forms a protective layer of zinc oxide when exposed to air, preventing rust even if the coating is damaged.

4. Human Kidney Functions and Urinary System

(a) Vital functions:

1. Removal of nitrogenous wastes (urea, uric acid).
2. Regulation of water and salt balance (osmoregulation).

(b) Diagram: A detailed diagram should include labeled kidneys, ureters, urinary bladder, and urethra.

5. Excretion and Excretory System

(a) Excretion is the removal of metabolic waste from the body.
(b) The nephron is the basic filtration unit in the kidney.
(c) Label the organs:

1. Kidneys (form urine).
2. Ureters (collect urine from the kidneys).
3. Urinary bladder (stores urine).

6. Image Formation by a Mirror

Given:
Object distance $u = -30 , text{cm}$,
Image distance $v = -60 , text{cm}$ (screen on the same side).
Nature: Concave mirror (real image).

Using the mirror formula:
$frac{1}{f} = frac{1}{v} – frac{1}{u}$
$f = -20 , text{cm}$

Magnification $M = frac{-v}{u}$:
$M = frac{-(-60)}{-30} = -2$

Height of image: $h_i = M times h_o = -2 times 2.4 , text{cm} = -4.8 , text{cm}$
The image is inverted.

7. Real Image with Magnification -1

Given: $M = -1$, $v = -40 , text{cm}$.
From $M = frac{-v}{u}$:
$u = -40 , text{cm}$

When the object is moved 20 cm closer:
New $u = -20 , text{cm}$. Using the mirror formula:
$frac{1}{f} = frac{1}{v} – frac{1}{u}$
$f = -20 , text{cm}$
New $v = -60 , text{cm}$.
Diagram: Include principal focus and object-image positioning.

8. Erect Image Using a Concave Mirror

(i) object distance range: Between the pole and the focus (less than 12 cm).
(ii) The image will be larger.
(iii) For $u = -24 , text{cm}$:
$frac{1}{f} = frac{1}{v} – frac{1}{u}$
$v = -24 , text{cm}$
The image is real, inverted, and of the same size as the object.
Diagram: Include pole, principal axis, and rays.

9. Resistance and Factors

Resistance depends on:

1. Length of conductor.
2. Cross-sectional area.
3. Material (resistivity).

Device: Rheostat.

Given: $l = 0.5 , text{m}, A = 0.01 , text{mm}^2, rho = 5 times 10^{-8} Omega , text{m}$.
$R = rho frac{l}{A} = 5 times 10^{-8} times frac{0.5}{0.01 times 10^{-6}}$
$R = 2.5 , Omega$

10. Thicker Wire

Wire $B$ is thicker as $R propto frac{rho}{A}$, and lower resistivity implies a larger cross-sectional area.

11. Electric Lamp and Circuit

(a) Total resistance: $R_{text{total}} = R_{text{lamp}} + R_{text{conductor}} = 20 + 4 = 24 , Omega$.
(b) Current: $I = frac{V}{R} = frac{6}{24} = 0.25 , text{A}$.
(c) Potential difference:

• Across lamp: $V = I times R_{text{lamp}} = 0.25 times 20 = 5 , text{V}$.
• Across conductor: $V = I times R_{text{conductor}} = 0.25 times 4 = 1 , text{V}$.
  (d) Power of lamp:
  $P = I^2 times R_{text{lamp}} = 0.25^2 times 20 = 1.25 , text{W}$.

Answers to 3-Mark Questions:

1. Properties utilized:
(a) Graphite is used in making electrodes because it conducts electricity and is inert to most chemical reactions.
(b) Electric wires are coated with PVC or rubber for insulation, ensuring safety from electric shocks.
(c) Metal alloys are used in bells and musical strings for their sonorous quality and resistance to wear.

2. Ore and chemical reactions:
(a) The ore is a carbonate ore. Steps to extract the metal:

1. Calcination: Heating the ore in limited oxygen to form an oxide.
2. Reduction: Converting the oxide to the metal using a reducing agent like carbon.
   (b) Copper displaces silver from silver nitrate, forming a silver coating on the coin.
   $text{Cu} + 2text{AgNO}_3 → text{Cu(NO}_3)_2 + 2text{Ag}$
   The solution turns blue due to copper nitrate formation.

3. Electrolysis of water:
(a) Gas at the cathode: Hydrogen; at the anode: Oxygen.
(b) Twice the volume of hydrogen is collected because water dissociates in a 2:1 ratio of hydrogen to oxygen.
(c) Test: Hydrogen burns with a popping sound.

4. Difference between Photosynthesis and Respiration:

5. Gaseous exchange:
(a) Oxygen diffuses from alveoli to blood and is transported bound to hemoglobin. CO₂ diffuses from tissues to blood and is exhaled.
(b) Hemoglobin is a protein in red blood cells that binds oxygen for transport.

6. Pathways of glucose breakdown:
Glucose undergoes:

1. Anaerobic respiration in yeast:
   $C_6H_{12}O_6 → 2C_2H_5OH + 2CO_2 + text{Energy}$
2. Aerobic respiration:
   $C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + text{Energy}$
   Diagram: Include glycolysis, Krebs cycle, and electron transport.

7. Fate of glucose:
(a) In yeast and lactobacillus:
$C_6H_{12}O_6 → 2C_3H_6O_3$ (lactic acid fermentation).
(b) In humans (aerobic respiration):
$C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + text{Energy}$

8. DNA Copying:
It is the process of creating identical copies of DNA during cell division, ensuring genetic information is passed to the next generation. Importance: Essential for heredity, evolution, and cell function.

9. Reasons:
(a) Acquired traits do not change DNA; hence they are not inherited.
(b) Humans interbreed freely and share a common gene pool.
(c) Variations ensure adaptation and evolution over generations.

10. Male or female child:
The sex of the child depends on whether the sperm carrying X or Y chromosome fertilizes the egg. Draw a flowchart showing $XX$ (female) and $XY$ (male).

11. Solar furnaces:
Concave mirrors are used. They focus sunlight to a single point, generating high temperatures.

12. Convex mirror properties:

1. The image is virtual and upright.
2. The image is diminished.
   Diagram: Include a convex mirror with rays diverging.

13. Magnification $+3$:
(i) Convex mirror.
(ii) The object is within the focal length of the mirror.
Diagram: Draw a ray diagram showing the upright and enlarged image.

14. Magnification $+1/3$:
(i) Concave mirror.
(ii) The object is beyond the center of curvature.
Diagram: Show diminished and inverted image.

15. Ray diagrams:
(i) Ray through the center of curvature reflects back on itself.
(ii) Ray parallel to the principal axis diverges as if from the focal point.
(iii) Ray through the focus reflects parallel to the axis.

16. Resistivity calculation:
Given $l = 1 , text{m}, r = 0.01 , text{cm}$, $R = 20 , Omega$:
$A = pi r^2 = pi (0.01 times 10^{-2})^2 , text{m}^2$
$rho = R frac{A}{l} approx 6.28 times 10^{-7} , Omega text{m}.$

17. Resistor combinations:
(i) For $R = 13.5 , Omega$: Combine two in parallel and add one in series.
(ii) For $R = 6 , Omega$: Combine all in parallel.

18. Electric fuse:
Due to its low melting points, fuse wire is made of tin or lead. It melts to break the circuit, preventing overloading.

19. Current in lamps:
Given $P = frac{V^2}{R}$, find currents for both bulbs:
For 100 W: $I = frac{100}{220} approx 0.45 , text{A}$.
For 60 W: $I = frac{60}{220} approx 0.27 , text{A}$.

20. Hormones and their glands:
(a) Thyroid: Thyroxine (regulates metabolism).
(b) Pituitary: Growth hormone (controls growth).
(c) Pancreas: Insulin (regulates blood sugar).

21. Reasons:
(a) The pituitary controls other glands.
(b) The pancreas secretes digestive enzymes and insulin.
(c) Adrenals prepare the body for emergencies (fight-or-flight response).

22. Plant hormones:
(a) Auxins: Cell elongation.
(b) Gibberellins: Stem growth.
(c) Cytokinins: Cell division.
(d) Abscisic acid: Stress responses.
(e) Ethylene: Fruit ripening.

NCERT Class 10 Science Most Important MCQs For Board Examination

1. Chemical Reactions and Equations

1. What type of reaction is observed when quicklime reacts with water?

   • (a) Displacement
   • (b) Combination
   • (c) Decomposition
   • (d) Redox
     Answer: (b) Combination

2. Which gas is evolved when hydrochloric acid reacts with a metal carbonate?

   • (a) Hydrogen
   • (b) Oxygen
   • (c) Carbon dioxide
   • (d) Chlorine
     Answer: (c) Carbon dioxide

3. What happens when zinc is added to a copper sulfate solution?

   • (a) Zinc displaces copper
   • (b) No reaction occurs
   • (c) Copper displaces zinc
   • (d) The solution turns green
     Answer: (a) Zinc displaces copper

2. Acids, Bases, and Salts

4. Which pH value indicates a strong acid?

   • (a) 7
   • (b) 1
   • (c) 10
   • (d) 14
     Answer: (b) 1

5. What is the common name for sodium bicarbonate?

   • (a) Washing soda
   • (b) Baking soda
   • (c) Limewater
   • (d) Caustic soda
     Answer: (b) Baking soda

6. Which acid is present in vinegar?

   • (a) Acetic acid
   • (b) Citric acid
   • (c) Lactic acid
   • (d) Hydrochloric acid
     Answer: (a) Acetic acid

3. Metals and Non-Metals

7. Which non-metal is a good conductor of electricity?

   • (a) Phosphorus
   • (b) Sulfur
   • (c) Carbon (Graphite)
   • (d) Bromine
     Answer: (c) Carbon (Graphite)

8. Which metal is stored under kerosene oil?

   • (a) Sodium
   • (b) Magnesium
   • (c) Copper
   • (d) Iron
     Answer: (a) Sodium

4. Carbon and Its Compounds

9. The functional group in ethanol is:

   • (a) –OH
   • (b) –COOH
   • (c) –CHO
   • (d) –COO
     Answer: (a) –OH

10. Which process is used for the manufacture of soap?

• (a) Esterification
• (b) Hydrogenation
• (c) Saponification
• (d) Substitution
  Answer: (c) Saponification

5. Periodic Classification of Elements

11. Which element has an atomic number of 16?

• (a) Oxygen
• (b) Sulfur
• (c) Phosphorus
• (d) Chlorine
  Answer: (b) Sulfur

12. What is the valency of magnesium?

• (a) 1
• (b) 2
• (c) 3
• (d) 4
  Answer: (b) 2

6. Life Processes

13. Which enzyme in saliva breaks down starch?

• (a) Pepsin
• (b) Amylase
• (c) Lipase
• (d) Trypsin
  Answer: (b) Amylase

14. Which part of the human digestive system absorbs water?

• (a) Stomach
• (b) Small intestine
• (c) Large intestine
• (d) Rectum
  Answer: (c) Large intestine

7. Control and Coordination

15. Which hormone controls blood sugar levels?

• (a) Thyroxine
• (b) Insulin
• (c) Adrenaline
• (d) Estrogen
  Answer: (b) Insulin

16. What is the functional unit of the nervous system?

• (a) Axon
• (b) Neuron
• (c) Dendrite
• (d) Synapse
  Answer: (b) Neuron

8. Heredity and Evolution

17. In Mendel’s experiment, what was the dominant trait in pea plants?

• (a) Wrinkled seeds
• (b) Tall plants
• (c) Yellow flowers
• (d) Short plants
  Answer: (b) Tall plants

18. What determines the sex of a child?

• (a) X chromosomes in the egg
• (b) X and Y chromosomes in the sperm
• (c) Both X chromosomes in the sperm and egg
• (d) Hormones
  Answer: (b) X and Y chromosomes in the sperm

9. Electricity

19. What is the unit of electric current?

• (a) Volt
• (b) Ampere
• (c) Ohm
• (d) Coulomb
  Answer: (b) Ampere

20. The resistance of a conductor depends on:

• (a) Length
• (b) Material
• (c) Cross-sectional area
• (d) All of the above
  Answer: (d) All of the above

10. Magnetic Effects of Electric Current

21. The SI unit of magnetic field strength is:

• (a) Tesla
• (b) Gauss
• (c) Henry
• (d) Weber
  Answer: (a) Tesla

22. The right-hand thumb rule is used to determine:

• (a) Magnetic field direction
• (b) Electric current flow
• (c) Resistance
• (d) Voltage drop
  Answer: (a) Magnetic field direction

11. Human Eye and the Colourful World

23. The least distance of distinct vision for a normal human eye is:

• (a) 5 cm
• (b) 10 cm
• (c) 25 cm
• (d) 50 cm
  Answer: (c) 25 cm

24. The splitting of white light into its component colors is called:

• (a) Reflection
• (b) Refraction
• (c) Dispersion
• (d) Diffraction
  Answer: (c) Dispersion

Here’s the continuation of MCQs for CBSE Class 10 Science:

12. Sources of Energy

25. Which of the following is a renewable source of energy?

• (a) Coal
• (b) Petroleum
• (c) Solar energy
• (d) Natural gas
  Answer: (c) Solar energy

26. What is the primary fuel used in thermal power plants?

• (a) Coal
• (b) Uranium
• (c) Biomass
• (d) Wind
  Answer: (a) Coal

27. What is the main advantage of using biogas over fossil fuels?

• (a) High efficiency
• (b) Environment-friendly
• (c) Unlimited supply
• (d) High calorific value
  Answer: (b) Environment-friendly

13. Our Environment

28. Which of the following is a biodegradable waste?

• (a) Plastic
• (b) Glass
• (c) Vegetable peels
• (d) Metal scraps
  Answer: (c) Vegetable peels

29. What is the main component of ozone?

• (a) O2
• (b) O3
• (c) CO2
• (d) NO2
  Answer: (b) O3

30. The main reasons for the depletion of ozone in the atmosphere is:

• (a) Carbon dioxide emissions
• (b) Chlorofluorocarbons (CFCs)
• (c) Deforestation
• (d) Greenhouse gases
  Answer: (b) Chlorofluorocarbons (CFCs)

14. Management of Natural Resources

31. “Reduce, Reuse, Recycle” is associated with:

• (a) Waste management
• (b) Food storage
• (c) Water conservation
• (d) Wildlife preservation
  Answer: (a) Waste management

32. Which practice conserves water in agriculture?

• (a) Excess irrigation
• (b) Sprinkler irrigation
• (c) Flood irrigation
• (d) Overuse of fertilizers
  Answer: (b) Sprinkler irrigation

33. Which forest product is renewable and sustainable?

• (a) Coal
• (b) Timber
• (c) Petroleum
• (d) Iron
  Answer: (b) Timber

15. Light Reflection and Refraction

34. A concave mirror is used in which of the following?

• (a) Rear-view mirrors
• (b) Solar furnaces
• (c) Torchlights
• (d) Both (b) and (c)
  Answer: (d) Both (b) and (c)

35. The speed of light is maximum in:

• (a) Air
• (b) Glass
• (c) Vacuum
• (d) Water
  Answer: (c) Vacuum

36. What happens to light when it passes from air to glass?

• (a) It speeds up
• (b) It slows down
• (c) It remains unchanged
• (d) It bends away from the normal
  Answer: (b) It slows down

16. Electricity

37. What is the SI unit of resistance?

• (a) Ampere
• (b) Ohm
• (c) Volt
• (d) Coulomb
  Answer: (b) Ohm

38. If two resistors of 4 Ω and 6 Ω are connected in parallel, the equivalent resistance will be:

• (a) 10 Ω
• (b) 2.4 Ω
• (c) 24 Ω
• (d) 5 Ω
  Answer: (b) 2.4 Ω

39. An electric current through a conductor produces:

• (a) Electric field only
• (b) Magnetic field only
• (c) Both electric and magnetic fields
• (d) None of these
  Answer: (c) Both electric and magnetic fields

17. Magnetic Effects of Electric Current

40. The direction of the magnetic field around a straight current-carrying conductor is given by:

• (a) Fleming’s left-hand rule
• (b) Right-hand thumb rule
• (c) Fleming’s right-hand rule
• (d) Ampere’s circuital law
  Answer: (b) Right-hand thumb rule

41. A solenoid behaves like a:

• (a) Permanent magnet
• (b) Temporary magnet
• (c) Neutral body
• (d) None of these
  Answer: (b) Temporary magnet

42. A device used to measure current in a circuit is:

• (a) Voltmeter
• (b) Ammeter
• (c) Galvanometer
• (d) Rheostat
  Answer: (b) Ammeter

18. Human Eye and the Colourful World

43. Myopia can be corrected using:

• (a) Convex lens
• (b) Concave lens
• (c) Cylindrical lens
• (d) None of these
  Answer: (b) Concave lens

44. What is the cause of the dispersion of light?

• (a) Reflection
• (b) Refraction
• (c) Different wavelengths of light
• (d) Scattering of light
  Answer: (c) Different wavelengths of light

19. Heredity and Evolution

45. Who is known as the father of genetics?

• (a) Darwin
• (b) Mendel
• (c) Lamarck
• (d) Watson
  Answer: (b) Mendel

46. Evolution is supported by the study of:

• (a) Fossils
• (b) Homologous structures
• (c) Analogous structures
• (d) All of these
  Answer: (d) All of these

20. Miscellaneous

47. Rusting is a process of:

• (a) Oxidation
• (b) Reduction
• (c) Sublimation
• (d) Electrolysis
  Answer: (a) Oxidation

48. What is the primary source of energy in a nuclear reactor?

• (a) Coal
• (b) Uranium
• (c) Plutonium
• (d) Solar energy
  Answer: (b) Uranium

49. Which of these is an artificial ecosystem?

• (a) Forest
• (b) Pond
• (c) Crop field
• (d) Desert
  Answer: (c) Crop field

50. The process of water conservation is called:

• (a) Harvesting
• (b) Irrigation
• (c) Rainwater harvesting
• (d) Defrosting
  Answer: (c) Rainwater harvesting