CBSE Class 10 Science — 30 Most Expected Questions Board Exam 2027
30 most expected questions for CBSE Class 10 Science board exam 2027. Physics (Electricity, Light, Magnetic Effects), Chemistry (Chemical Reactions, Acids Bases, Carbon Compounds, Metals), Biology (Life Processes, Heredity, Reproduction). SQP + PYQ based predictions.
In short: 30 questions that cover 75+ marks of the 80-mark CBSE Class 10 Science paper. Each question is derived from the official 2027 SQP, previous year papers (2024-2026), and CBSE unit-wise weightage. Physics, Chemistry, and Biology are covered in proportion to their marks allocation. For each question: the topic, expected marks, section, and what the examiner specifically looks for in the marking scheme. Also see our Maths expected questions for Class 10.
How This List Was Built
Source
What We Analysed
CBSE Official SQP 2027
Released Sep 21, 2026. Same pattern as 2025-26 confirmed.
Previous Year Papers (2024-2026)
3 years of actual board papers. Repeated question types identified.
CBSE Unit-Wise Weightage
Chemical Substances: 25, World of Living: 23, Natural Phenomena: 12, Effects of Current: 13, Natural Resources: 7. See the full chapter-wise weightage breakdown.
Life Processes, Control and Coordination, Reproduction, Heredity and Evolution
23
#11-20
Natural Phenomena (Physics)
Light — Reflection and Refraction
12
#21-24
Effects of Current (Physics)
Electricity, Magnetic Effects
13
#25-28
Natural Resources
Our Environment, Sustainable Development
7
#29-30
Total
13 chapters
80
30 questions
Chemistry — Chemical Reactions and Equations (5 Marks)
#
Expected Question
Type
Marks
Section
1
Write balanced chemical equations for given reactions. Identify the type (combination, decomposition, displacement, double displacement, redox).
SA / MCQ
1-3
A / C
2
Explain the different types of chemical reactions with one example each. Write balanced equations for: thermal decomposition of ferrous sulphate, electrolytic decomposition of water, photolytic decomposition of silver chloride.
SA / LA
3-5
C / D
What the examiner wants
Q1: Correct molecular formula + correct balancing + state symbols (s, l, g, aq) + conditions (heat, sunlight, electricity). Missing state symbols = lose 0.5 marks.
Q2: For each reaction type: name, general form, one specific balanced example. Conditions above/below the arrow must be shown.
PYQ track: Appeared in 100% of papers (2024-2026). 5 marks minimum guaranteed from this chapter.
Chemistry — Acids, Bases, and Salts (5 Marks)
#
Expected Question
Type
Marks
Section
3
What happens when an acid or base reacts with a metal? Write the balanced equation. What gas is produced and how do you test for it?
SA
3
C
4
Explain the pH scale. What is the pH range of acidic, neutral, and basic solutions? Why does a change in pH matter in everyday life (soil, digestion, tooth decay)?
SA / Case-Based
3-4
C / E
Key facts to memorize
Substance
pH
Nature
Gastric juice (HCl)
~1.2
Strongly acidic
Lemon juice
~2.2
Acidic
Pure water
7.0
Neutral
Blood
7.35-7.45
Slightly basic
Milk of magnesia
~10
Basic
Sodium hydroxide (1M)
~14
Strongly basic
Important equations
Reaction
Balanced Equation
Acid + Metal
2HCl + Zn → ZnCl₂ + H₂↑
Acid + Metal Carbonate
2HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂↑
Acid + Base (Neutralisation)
NaOH + HCl → NaCl + H₂O
Chlor-alkali process
2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂(g) + H₂(g)
Chemistry — Metals and Non-Metals (5 Marks)
#
Expected Question
Type
Marks
Section
5
Explain the reactivity series of metals. Why does copper not react with dilute HCl but zinc does? Write the equations.
SA
3
C
6
Describe the extraction of metals from their ores (give the steps for a medium-reactivity metal like iron or zinc).
LA
5
D
What the examiner wants
Q5: List at least 5 metals in order. Explain using reactivity that metals above hydrogen displace it from acids; metals below do not. Write equations.
Q6: Three steps: (1) Concentration/enrichment of ore, (2) Reduction to metal (roasting/calcination + reduction with carbon), (3) Refining (electrolytic refining). Equations for each step. Diagram of electrolytic refining if asked = extra mark.
Chemistry — Carbon and Its Compounds (5 Marks)
#
Expected Question
Type
Marks
Section
7
What is a homologous series? Write the molecular formula, structural formula, and IUPAC name for the first three members of the alkane series.
SA
3
C
8
Explain with equations: (a) esterification reaction, (b) saponification reaction, (c) addition reaction of unsaturated hydrocarbons.
SA / LA
3-5
C / D
Key equations
Reaction
Equation
Key Detail
Combustion of ethanol
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
Blue flame, exothermic
Esterification
CH₃COOH + C₂H₅OH →(H₂SO₄) CH₃COOC₂H₅ + H₂O
Fruity-smelling ester
Saponification
Fat/Oil + NaOH → Soap + Glycerol
Base-catalysed hydrolysis
Addition (ethene)
CH₂=CH₂ + H₂ →(Ni catalyst) CH₃-CH₃
Unsaturated → Saturated
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State Mendeleev's periodic law. List 2 achievements and 2 limitations of his periodic table. How does the modern periodic table overcome these limitations?
SA / LA
3-5
C / D
10
Explain the trends in the modern periodic table: (a) atomic size across a period and down a group, (b) metallic character, (c) electronegativity. Give reasons for each trend.
SA / MCQ
2-3
B / C
Trends summary table
Property
Across a Period (L→R)
Down a Group (Top→Bottom)
Reason
Atomic size
Decreases
Increases
Across: more nuclear charge, same shell. Down: new shells added.
Metallic character
Decreases
Increases
Tendency to lose electrons changes.
Electronegativity
Increases
Decreases
Attraction for bonding electrons.
Ionisation energy
Increases
Decreases
Outer electron closer/farther from nucleus.
Valency
1→4 then 4→0
Same within a group
Number of valence electrons.
Biology — Life Processes (8 Marks)
#
Expected Question
Type
Marks
Section
11
Draw a neat diagram of the human digestive system. Label any 6 parts. Describe the role of (a) HCl in the stomach, (b) bile juice, (c) pancreatic enzymes.
LA
5
D
12
Explain the process of photosynthesis. Write the balanced equation. Draw and label the cross-section of a leaf showing where photosynthesis occurs.
SA / LA
3-5
C / D
13
Describe the mechanism of breathing in humans. Explain the role of the diaphragm. What is the difference between respiration and breathing?
SA
3
C
14
Draw a neat diagram of the human excretory system. Label: kidney, ureter, urinary bladder, urethra. Explain the role of nephrons in urine formation (filtration, reabsorption, secretion).
LA
5
D
PYQ pattern
Digestive system diagram with labelling: appeared 2024, 2025, 2026. Almost guaranteed.
Photosynthesis equation + experiment (iodine test for starch): appeared 2024, 2026.
Nephron structure and urine formation: appeared 2025, 2026.
At least 2 of these 4 questions will appear as 3-mark or 5-mark questions.
Biology — Control and Coordination (5 Marks)
#
Expected Question
Type
Marks
Section
15
Draw a neat diagram of the reflex arc. Label: receptor, sensory neuron, relay neuron, motor neuron, effector. Explain how a reflex action works with an example.
SA / LA
3-5
C / D
16
Differentiate between the nervous system and endocrine system (at least 4 points). Name the hormones produced by (a) thyroid, (b) pancreas, (c) adrenal glands and their functions.
SA
3
C
Biology — How Do Organisms Reproduce (5 Marks)
#
Expected Question
Type
Marks
Section
17
Draw a neat diagram of the human male reproductive system OR female reproductive system. Label any 6 parts. Explain the function of any 3 parts.
LA
5
D
18
What are sexually transmitted diseases? Name 2 bacterial and 2 viral STDs. What are the methods to prevent them?
SA
3
C
PYQ pattern
Male/female reproductive system diagram: appeared every year (2024-2026). Alternates between male and female. 2027 prediction: female reproductive system (male was asked in 2026).
Biology — Heredity and Evolution (5 Marks)
#
Expected Question
Type
Marks
Section
19
Explain Mendel's monohybrid cross using the example of tall and dwarf pea plants. Show the F₁ and F₂ generations. What is the phenotype and genotype ratio in F₂?
LA / Case-Based
4-5
D / E
20
What are homologous and analogous organs? Give 2 examples of each. How do they provide evidence for evolution?
SA
3
C
Key data to memorize
Cross
F₁
F₂ Phenotype Ratio
F₂ Genotype Ratio
Monohybrid (Tt × Tt)
All Tall (Tt)
3 Tall : 1 Dwarf
1 TT : 2 Tt : 1 tt
Dihybrid (TtRr × TtRr)
All Tall Round
9:3:3:1
16 combinations
Sex determination
XX × XY
1 Male : 1 Female
XX(girl), XY(boy)
Physics — Light: Reflection and Refraction (12 Marks)
#
Expected Question
Type
Marks
Section
21
Derive the mirror formula (1/f = 1/v + 1/u) for a concave mirror. OR derive the relationship between focal length and radius of curvature (f = R/2).
LA
5
D
22
A convex lens forms an image at a specified position. Given object distance and focal length, find image distance and magnification. State the nature of the image (real/virtual, inverted/erect, magnified/diminished).
SA / Numerical
3
C
23
Draw ray diagrams for image formation by (a) a concave mirror when the object is between F and C, and (b) a convex lens when the object is beyond 2F.
SA / MCQ
2-3
B / C
24
State Snell's law of refraction. Define refractive index. An object is placed at 30 cm from a lens of focal length 20 cm. Find the image position.
Numerical / MCQ
2-3
A / B / C
Key formulas
Formula
Expression
Application
Mirror formula
1/f = 1/v + 1/u
Concave and convex mirrors
Lens formula
1/f = 1/v - 1/u
Convex and concave lenses
Magnification (mirror)
m = -v/u = h'/h
Image size and nature
Magnification (lens)
m = v/u = h'/h
Image size and nature
Power of lens
P = 1/f (in metres)
Unit: Dioptre (D)
Snell's law
n = sin i / sin r
Refractive index
Sign convention reminders
Object distance (u) is ALWAYS negative (object on left of mirror/lens).
For concave mirror: f is negative. For convex mirror: f is positive.
For convex lens: f is positive. For concave lens: f is negative.
Physics — Electricity (8 Marks)
#
Expected Question
Type
Marks
Section
25
State Ohm's law. Draw the V-I graph for a metallic conductor. An electric circuit has resistors in series and parallel — find the total resistance and current in the circuit.
LA / Numerical
5
D
26
Derive the formula for equivalent resistance of resistors connected (a) in series, (b) in parallel.
SA
3
C
27
Calculate the electrical energy consumed by a device in kWh. Electric bill calculation problem: given power rating, hours of use, rate per unit.
Numerical / Case-Based
3-4
C / E
Key formulas
Formula
Expression
Ohm's law
V = IR
Power
P = VI = I²R = V²/R
Energy
E = Pt = VIt
1 kWh
3.6 × 10⁶ J
Series resistance
R = R₁ + R₂ + R₃
Parallel resistance
1/R = 1/R₁ + 1/R₂ + 1/R₃
Heating effect
H = I²Rt
PYQ pattern
Circuit numerical (series-parallel combination): appeared 2024, 2025, 2026 as 5-mark question.
Electric bill calculation: appeared 2024, 2026 as 3-mark or case-based question.
Physics — Magnetic Effects of Electric Current (5 Marks)
#
Expected Question
Type
Marks
Section
28
State Fleming's Left Hand Rule. Draw a labelled diagram of an electric motor. Explain its working principle.
SA / LA
3-5
C / D
What the examiner wants
Fleming's Left Hand Rule: Thumb = Force, Index finger = Field (N→S), Middle finger = Current. State clearly with diagram of hand.
Electric motor diagram: rectangular coil, magnets (N-S poles), split ring commutator, brushes, axle. Label all parts.
Working: current in coil → force on arms (FLHR) → rotation → commutator reverses current every half turn → continuous rotation.
Biology / Environment — Our Environment (5 Marks)
#
Expected Question
Type
Marks
Section
29
What is an ecosystem? Explain the components (biotic and abiotic). Draw a food chain with 4 trophic levels. Explain the 10% law of energy transfer.
SA / Case-Based
3-4
C / E
30
What is the ozone layer? How is it formed? What causes ozone depletion? What are the consequences and how can we protect it?
SA
3
C
Key facts
Concept
Details
10% Law
Only 10% of energy transfers from one trophic level to the next.
Food chain example
Grass → Grasshopper → Frog → Snake → Eagle
Ozone formula
O₃ (formed from O₂ by UV radiation in stratosphere)
Ozone depletion cause
CFCs (chlorofluorocarbons) from refrigerants, aerosols
Biodegradable waste
Paper, food scraps, cotton — broken down by microorganisms
Non-biodegradable waste
Plastic, glass, aluminium — persist in environment
Q1. Are these 30 questions enough for the full 80-mark paper?
These 30 cover every question TYPE that appears. The actual paper has 38 questions, but many MCQs are simple recall. If you master these 30 types, you are prepared for 75+ marks.
Q2. Which sections of Science carry the most marks?
Chemistry: 25 marks (highest). Biology: 23 marks. Physics (Light + Electricity + Magnetism): 25 marks. Environment: 7 marks.
Q3. Should I focus more on diagrams or equations?
Both. Biology marks depend heavily on labelled diagrams (digestive system, nephron, reproductive system, reflex arc). Chemistry marks depend on balanced equations. Physics marks depend on circuit diagrams and ray diagrams. Diagrams carry 1-2 marks each in the marking scheme.
Q4. Is NCERT enough for Science?
Yes, for 70+ marks. CBSE questions come directly from NCERT textbook. For 80/80, add the official SQP + 2-3 previous year papers. If you have practicals coming up, check our Science practical exam guide.
Q5. How should I handle assertion-reason questions?
Read the assertion first. Then read the reason. Ask: (1) Is the assertion true? (2) Is the reason true? (3) Does the reason correctly explain the assertion? The most common trap is when both are true but the reason does not explain the assertion.
Q6. What if I cannot draw a diagram neatly in the exam?
Use a pencil first, then trace over with pen. Label with straight lines using a ruler. The diagram does not need to be artistic — it needs to be clear and correctly labelled. Examiners award marks for correct labels, not beauty. For more tips on answer presentation, see our guide on how to write answers for maximum marks.
