CBSE Class 10th Science Top 50 Questions Answer With Solution// Annual Exam 2026 CbSe Board Class 10th Science Top 50 Questions with answers

- Mains Education

- CBSE Class 10 Science (2025–26)

- 50 Practice Questions with Answer Competency‑Based - Exam‑Ready

- Instructor: [Sanjay Sir] | mainseducation | © 2025

- Batch: Board Exams 2025–26

Section A — MCQs

1) Fe + CuSO4 → FeSO4 + Cu is which reaction? Answer: Displacement.

2) Which indicator turns pink in base? Answer: Phenolphthalein.

3) Which metal is stored under kerosene? Answer: Sodium.

4) Single-layer hexagonal carbon allotrope? Answer: Graphene.

5) Basic unit of life? Answer: Cell.

6) Most nutrient absorption occurs in? Answer: Small intestine.

7) Plant hormone promoting elongation? Answer: Auxin.

8) Asexual reproduction in yeast? Answer: Budding.

9) Law explaining segregation during gamete formation? Answer: Law of Segregation.

10) Dentist’s mirror? Answer: Concave mirror.

11) Power +2 D; focal length? Answer: +0.5 m.

12) Current through 10 Ω at 5 V? Answer: 0.5 A.

13) Direction of induced current rule? Answer: Fleming’s right‑hand rule.

14) Highest weightage section in 2026 paper? Answer: Biology.

15) Marks for “Chemical Substances – Nature and Behaviour”? Answer: 25 marks.

16) Total questions in 2026 Science paper? Answer: 39.

Section A — Assertion–Reason

17) Neutralization forms salt and water; due to H+ combining with OH–. Answer: Both true; reason explains.

18) Metals conduct due to free electrons; metallic bonding has delocalized electrons. Answer: Both true; reason explains.

19) Eye lens accommodates by ciliary muscles changing curvature. Answer: Both true; reason explains.

20) In series, Req increases; same current flows. Answer: Both true; reason not full explanation.

Section B — Very Short Answer (2 marks)

21) Rancidity and one prevention. Answer: Oxidative spoilage of fats/oils; prevent via antioxidants/airtight, dark storage.

22) Two indicator differences for acids/bases. Answer: Litmus and phenolphthalein color changes.

23) Why use alloys? Answer: Better strength, hardness, corrosion resistance; tailored properties.

24) Site/process of gas exchange in humans. Answer: Alveoli in lungs.

25) Homologous organs + example. Answer: Same basic structure, different function; human and whale forelimbs.

26) State Ohm’s law and formula. Answer: V ∝ I at constant temperature; V = IR.

Section C — Short Answer (3 marks)

27) Reaction of Zn with dil. H2SO4; type. Answer: Zn + H2SO4 → ZnSO4 + H2 (displacement).

28) pH of salts: strong acid–strong base vs strong acid–weak base. Answer: NaCl ~ neutral; NH4Cl acidic.

29) Three metal vs non‑metal properties. Answer: Metals malleable/ductile/conduct; non‑metals brittle/poor conductors/dull.

30) Role of stomata. Answer: Gas exchange and transpiration via guard cells.

31) Sex determination in humans. Answer: Father X or Y; XX female, XY male.

32) Mirror/lens formula and symbols. Answer: 1/f = 1/v + 1/u; f focal length, v image distance, u object distance.

33) Series vs parallel (I, V, Req). Answer: Series: same I, V adds, R increases; Parallel: same V, I adds, R decreases.

Section D — Competency Based (3 marks)

34) 6 Ω and 3 Ω in parallel across 6 V: total current. Answer: Rp=2 Ω; I=3 A.

35) Real, inverted, smaller image—identify lens and object position. Answer: Convex lens; object beyond 2F.

36) Metal M makes H2 with HCl; oxide forms base in water. Answer: Active metal forming basic oxide; e.g., Na/Ca.

Section E — Case Based (4 marks)

37) HCl + CaCO3 with effervescence; lime water turns milky.

a) Reaction: CaCO3 + 2HCl → CaCl2 + H2O + CO2

b) Gas: CO2

c) Type: Acid–carbonate reaction

d) Reason for milkiness: CaCO3 formation in lime water.

38) Normal ECG but fatigue; anemia suspected.

a) Oxygen‑carrying pigment: Hemoglobin

b) Deficiency: Iron

c) Tissues get oxygen via: Systemic circulation

d) Blood part carrying nutrients: Plasma

39) Coil with soft iron core picks nails on current.

a) Device: Electromagnet

b) Rule for straight conductor: Right‑hand thumb rule

c) Effect of higher current: Stronger field

d) Why soft iron: Enhances field, loses magnetism quickly when current stops.

Section F — Long Answer (5 marks)

40) Human excretory system and urine formation. Answer: Kidneys with nephrons; filtration at glomerulus, selective reabsorption in tubules, tubular secretion; urine → pelvis → ureter → bladder → urethra.

41) Periodic trends. 

Answer: Across period: atomic size decreases, metallic character decreases; down group: size increases, metallic character increases; valency follows group and remains constant down a group.

42) Equivalent resistance derivations with example. 

Answer: Series Rs=R1+R2; Parallel 1/Rp=1/R1+1/R2; Example R1=4 Ω, R2=6 Ω → Rs=10 Ω; Rp=2.4 Ω.

Section G — Mixed Objective/Short

43) Salt from strong base + weak acid giving basic pH. 

Answer: Sodium acetate.

44) Why plaster of Paris for casts; setting reaction. 

Answer: Fast setting to gypsum; CaSO4·½H2O + 1½H2O → CaSO4·2H2O.

45) Two contraception methods. Answer: Condoms; oral pills or Copper‑T.

46) Define evolution and one evidence. 

Answer: Change in allele frequencies over generations; fossils/homologous structures.

47) Concave mirror gives same‑size inverted image—object position. Answer: At center of curvature.

48) Joule’s law of heating + application. 

Answer: H ∝ I^2 R t; used in heaters/fuses.

49) Series bulbs—one fuses. 

Answer: All go off.

50) Internal assessment (2025–26) marks and components. 

Answer: 20 marks; periodic assessment, practicals/enrichment, portfolio.