CBSE Class 10 Science Sample Paper 2027 with Solutions PDF — Complete Guide

In short: CBSE Class 10 Science Sample Paper 2027 has 39 questions across 5 sections — 80 marks in 3 hours. Section A has 20 MCQs, Section B has 6 questions (2 marks), Section C has 7 questions (3 marks), Section D has 3 questions (5 marks), and Section E has 3 case-based questions (4 marks). Physics, Chemistry, and Biology are equally weighted. This guide covers complete solutions, diagrams, and scoring strategies.

Paper Pattern 2027

Exam Structure

Section-wise Breakdown

Chapter-wise Weightage 2027

High-Weightage Chapters

Section A — MCQs (20 × 1 = 20 Marks)

Chemistry MCQs

Q1. A solution reacts with crushed egg shells to give a gas that turns lime water milky. The solution contains:

• (a) NaCl
• (b) HCl
• (c) LiCl
• (d) KCl

Solution: Egg shells contain CaCO₃. When acid reacts with carbonate, CO₂ is released which turns lime water milky. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑

Answer: (b) HCl

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Q2. What happens when dilute hydrochloric acid is added to iron filings?

• (a) Hydrogen gas and iron chloride are produced
• (b) Chlorine gas and iron hydroxide are produced
• (c) No reaction takes place
• (d) Iron salt and water are produced

Solution: Fe + 2HCl → FeCl₂ + H₂↑ Iron displaces hydrogen from acid (more reactive than hydrogen).

Answer: (a) Hydrogen gas and iron chloride are produced

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Q3. Which of the following is NOT a characteristic of carbon compounds?

• (a) They have low melting and boiling points
• (b) They are good conductors of electricity
• (c) They show isomerism
• (d) They undergo combustion reactions

Solution: Carbon compounds are covalent compounds with weak intermolecular forces. They are poor conductors of electricity.

Answer: (b) They are good conductors of electricity

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Biology MCQs

Q4. The blood vessel that carries blood from the lungs to the heart is:

• (a) Pulmonary artery
• (b) Pulmonary vein
• (c) Aorta
• (d) Vena cava

Solution: Pulmonary vein carries oxygenated blood from lungs to left atrium of heart. Pulmonary artery carries deoxygenated blood from heart to lungs.

Answer: (b) Pulmonary vein

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Q5. In human females, the fertilization of egg by sperm takes place in:

• (a) Uterus
• (b) Ovary
• (c) Fallopian tube (Oviduct)
• (d) Vagina

Solution: Fertilization occurs in the fallopian tube (oviduct). The fertilized egg then travels to the uterus for implantation.

Answer: (c) Fallopian tube (Oviduct)

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Q6. Which of the following is NOT a function of stomata?

• (a) Exchange of gases
• (b) Transpiration
• (c) Photosynthesis
• (d) Absorption of water

Solution: Stomata allow gas exchange and transpiration. Water absorption is done by roots, not stomata.

Answer: (d) Absorption of water

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Physics MCQs

Q7. A concave mirror produces a real, inverted image of the same size as the object. The object is placed at:

• (a) Focus
• (b) Centre of curvature
• (c) Between focus and centre of curvature
• (d) Beyond centre of curvature

Solution: When object is at C (centre of curvature), image is at C, real, inverted, and same size.

Answer: (b) Centre of curvature

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Q8. The SI unit of electric current is:

• (a) Volt
• (b) Ohm
• (c) Ampere
• (d) Watt

Solution: Electric current is measured in Ampere (A). 1 Ampere = 1 Coulomb/second

Answer: (c) Ampere

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Q9. Two resistors of 4Ω and 6Ω are connected in parallel. The equivalent resistance is:

• (a) 10Ω
• (b) 2.4Ω
• (c) 24Ω
• (d) 0.4Ω

Solution: For parallel: 1/Req = 1/R₁ + 1/R₂ 1/Req = 1/4 + 1/6 = (3+2)/12 = 5/12 Req = 12/5 = 2.4Ω

Answer: (b) 2.4Ω

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Q10. The phenomenon of electromagnetic induction was discovered by:

• (a) Oersted
• (b) Faraday
• (c) Ampere
• (d) Fleming

Solution: Michael Faraday discovered electromagnetic induction in 1831.

Answer: (b) Faraday

Section B — Very Short Answer (6 × 2 = 12 Marks)

Q21. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Solution: Iron is more reactive than copper. Iron displaces copper from copper sulphate solution.

Fe + CuSO₄ → FeSO₄ + Cu

• Blue colour of CuSO₄ fades (Cu²⁺ ions removed)
• Green colour of FeSO₄ appears (Fe²⁺ ions formed)
• Reddish-brown copper deposits on iron nail

Answer: Iron displaces copper from the solution (displacement reaction), changing blue CuSO₄ to green FeSO₄.

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Q22. What is the role of acid in our stomach? What happens when there is excess acid in the stomach?

Solution: Role of HCl in stomach:

1. Kills bacteria in food
2. Activates pepsinogen to pepsin (protein-digesting enzyme)
3. Provides acidic medium (pH 1.5-2) for pepsin action

Excess acid causes:

• Acidity/heartburn
• Indigestion
• Ulcers (in severe cases)

Remedy: Antacids (milk of magnesia, baking soda) neutralize excess acid.

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Q23. Draw a diagram of human brain and label: (i) Cerebrum (ii) Cerebellum

Solution:

[Diagram of Human Brain - Side View]

        _______________
       /               \
      /    CEREBRUM     \  ← (i) Largest part, thinking, memory
     |                   |
     |                   |
      \                 /
       \_______________/
              |
         CEREBELLUM  ← (ii) Balance, posture, coordination
              |
         MEDULLA
              |
        SPINAL CORD

Labels:

• (i) Cerebrum — Controls thinking, memory, intelligence, voluntary actions
• (ii) Cerebellum — Controls balance, posture, coordination of movements

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Q24. An object is placed at a distance of 30 cm from a concave mirror of focal length 15 cm. Find the position and nature of the image.

Solution: Given: u = -30 cm, f = -15 cm (concave mirror)

Using mirror formula: 1/v + 1/u = 1/f 1/v + 1/(-30) = 1/(-15) 1/v = -1/15 + 1/30 1/v = (-2 + 1)/30 = -1/30 v = -30 cm

Position: 30 cm in front of mirror (same side as object) Nature: Real, inverted, same size (since v = u)

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Section C — Short Answer (7 × 3 = 21 Marks)

Q27. What is a homologous series? Write any two characteristics. Give an example.

Solution: Definition: A homologous series is a group of organic compounds with the same functional group and similar chemical properties, where successive members differ by -CH₂- unit.

Characteristics:

1. Same general formula (e.g., CₙH₂ₙ₊₂ for alkanes)
2. Same functional group
3. Similar chemical properties
4. Gradual change in physical properties (boiling point, melting point increase with molecular mass)
5. Successive members differ by -CH₂- (14 u mass difference)

Example: Alkane series

• Methane: CH₄
• Ethane: C₂H₆
• Propane: C₃H₈
• Butane: C₄H₁₀

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Q28. Explain the process of nutrition in Amoeba with the help of a diagram.

Solution: Amoeba shows holozoic nutrition through the following steps:

1. Ingestion: Amoeba engulfs food (bacteria, algae) using pseudopodia. Food is enclosed in a food vacuole.

2. Digestion: Digestive enzymes are secreted into the food vacuole. Complex food is broken into simpler substances.

3. Absorption: Digested food is absorbed into the cytoplasm.

4. Assimilation: Absorbed food is used for energy and growth.

5. Egestion: Undigested food is expelled by rupturing the cell membrane.

[Diagram: Nutrition in Amoeba]

    Pseudopodia extending
         ↓
    ___________
   /           \
  |   Food      |  ← Food particle being engulfed
  |  Vacuole    |
  |    (•)      |  ← Nucleus
   \___________/
         ↓
    Food vacuole formed

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Q29. Derive the expression for the equivalent resistance when three resistors R₁, R₂, and R₃ are connected in series.

Solution: In series connection:

• Same current (I) flows through all resistors
• Total voltage = Sum of individual voltages

Let V₁, V₂, V₃ be voltages across R₁, R₂, R₃ respectively.

By Ohm's law: V₁ = IR₁, V₂ = IR₂, V₃ = IR₃

Total voltage: V = V₁ + V₂ + V₃ V = IR₁ + IR₂ + IR₃ V = I(R₁ + R₂ + R₃)

If Req is equivalent resistance: V = IReq

Therefore: Req = R₁ + R₂ + R₃

In series, equivalent resistance is the sum of individual resistances.

Section D — Long Answer (3 × 5 = 15 Marks)

Q33. (a) What is meant by refraction of light? State the laws of refraction. (b) A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from it? Why?

Solution:

(a) Refraction of Light: The bending of light when it passes from one transparent medium to another is called refraction.

Laws of Refraction (Snell's Law):

First Law: The incident ray, the refracted ray, and the normal to the interface at the point of incidence, all lie in the same plane.

Second Law: The ratio of sine of angle of incidence to the sine of angle of refraction is constant for a given pair of media.

sin i / sin r = constant = n₂₁ (refractive index)

(b) Light bends towards the normal.

Reason:

• Air is optically rarer medium (n = 1.0)
• Water is optically denser medium (n = 1.33)
• When light travels from rarer to denser medium, it slows down
• This causes the light ray to bend towards the normal

[Diagram]
        Normal
           |
    Air    |    
   --------|--------
           |\
    Water  | \  Refracted ray
           |  \
           |   (bends towards normal)

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Q34. (a) Draw a diagram of the human excretory system and label: (i) Kidney (ii) Ureter (iii) Urinary bladder (iv) Urethra

(b) Explain the process of urine formation in kidneys.

Solution:

(a) Diagram of Human Excretory System:

         Right Kidney    Left Kidney
              ___            ___
             /   \          /   \
            |     |        |     |
             \___/          \___/
               |              |
               |   Ureters    |
               |      ↓       |
               |______|_______|
                      |
              Urinary Bladder
                   (   )
                      |
                   Urethra
                      ↓

Labels:

• (i) Kidney — Bean-shaped organs that filter blood
• (ii) Ureter — Tubes carrying urine from kidney to bladder
• (iii) Urinary bladder — Stores urine temporarily
• (iv) Urethra — Tube through which urine is expelled

(b) Process of Urine Formation:

Urine formation occurs in nephrons through three steps:

1. Glomerular Filtration (Ultrafiltration):

• Blood enters glomerulus under high pressure
• Small molecules (water, glucose, salts, urea) filter into Bowman's capsule
• Large molecules (proteins, blood cells) remain in blood
• Filtrate formed = 180 L/day

2. Tubular Reabsorption:

• Useful substances reabsorbed in proximal tubule
• Glucose, amino acids, salts, water reabsorbed into blood
• About 99% of filtrate is reabsorbed

3. Tubular Secretion:

• Additional waste (H⁺, K⁺, urea) secreted from blood into tubule
• Maintains blood pH and ionic balance

Final urine: About 1.5-2 L/day, containing urea, excess salts, water.

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Q35. (a) What is an electromagnet? How is it different from a permanent magnet? (b) Draw a labelled diagram of an electric motor. State its principle.

Solution:

(a) Electromagnet: An electromagnet is a temporary magnet made by winding an insulated copper wire around a soft iron core and passing electric current through it.

(b) Electric Motor:

Principle: An electric motor works on the principle that a current-carrying conductor placed in a magnetic field experiences a force (Fleming's Left Hand Rule).

[Diagram of Electric Motor]

         N ←――――――――――――→ S
              |      |
              |  AB  |
         _____|______|_____
        |     ↑      ↓     |
        |   Coil ABCD      |
        |_____|______|_____|
              |      |
           Split Ring Commutator
              |      |
           Brushes (B₁, B₂)
              |
           Battery

Components:

• Rectangular coil ABCD
• Strong permanent magnet (N-S poles)
• Split ring commutator (reverses current direction)
• Carbon brushes (maintain contact)
• Axle (rotation axis)

Working: Current flows through coil → coil experiences force → coil rotates → commutator reverses current → rotation continues.

Section E — Case-Based Questions (3 × 4 = 12 Marks)

Case Study 1: Electricity in Daily Life

A household uses various electrical appliances. The following table shows the power rating and usage time of some appliances:

Q36.

(i) Calculate the energy consumed by the fan in one day.

Solution: Energy = Power × Time Energy = 75 W × 10 h = 750 Wh = 0.75 kWh

Answer: 0.75 kWh or 750 Wh

(ii) Which appliance consumes maximum energy in a day?

Solution:

• LED Bulb: 10 × 6 = 60 Wh
• Fan: 75 × 10 = 750 Wh
• TV: 100 × 4 = 400 Wh
• Refrigerator: 150 × 24 = 3600 Wh

Answer: Refrigerator (3600 Wh = 3.6 kWh)

(iii) If electricity costs ₹5 per unit (kWh), calculate the monthly bill for the refrigerator (30 days).

Solution: Daily consumption = 3.6 kWh Monthly consumption = 3.6 × 30 = 108 kWh Monthly bill = 108 × ₹5 = ₹540

Answer: ₹540

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Case Study 2: Human Reproduction

The human reproductive system ensures continuation of species. The diagram shows the female reproductive system.

Q37.

(i) Name the organ where fertilization takes place.

Answer: Fallopian tube (Oviduct)

(ii) What is the function of the placenta?

Solution: Functions of placenta:

1. Provides nutrients (glucose, oxygen) from mother to foetus
2. Removes waste (CO₂, urea) from foetus to mother
3. Acts as a barrier against pathogens
4. Produces hormones (progesterone, estrogen) to maintain pregnancy

Answer: Placenta provides nutrients and oxygen to the foetus and removes waste products.

(iii) Why is it important that the testes are located outside the abdominal cavity?

Solution: Sperm production (spermatogenesis) requires a temperature 2-3°C lower than body temperature. The scrotum, located outside the body, maintains this lower temperature for optimal sperm production.

Answer: Testes need lower temperature (2-3°C below body temperature) for sperm formation.

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Case Study 3: Chemical Reactions

When a magnesium ribbon is burnt in air, it produces a white powder with a bright flame.

Q38.

(i) Write the balanced chemical equation for this reaction.

Solution: 2Mg + O₂ → 2MgO

Answer: 2Mg + O₂ → 2MgO

(ii) What type of chemical reaction is this? Give two reasons.

Solution: This is a combination reaction (two substances combine to form one product).

It is also an oxidation reaction (magnesium gains oxygen).

Reasons:

1. Two reactants (Mg and O₂) combine to form one product (MgO)
2. Magnesium is oxidized (gains oxygen)
3. Heat and light are released (exothermic)

(iii) What is the nature of magnesium oxide? How can you test it?

Solution: Magnesium oxide is basic in nature.

Test: Dissolve MgO in water to form Mg(OH)₂. Add red litmus paper — it turns blue (confirms basic nature).

MgO + H₂O → Mg(OH)₂ (Magnesium hydroxide - base)

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