At a glance
- Board paper
- 80 marks, 3 hours
- Internal assessment
- 20 marks
- Heaviest units
- Chemistry 25, Biology 25
- Competency split
- 50% knowledge, 30% application, 20% analysis
- Sample paper
- 39 questions in biology, chemistry and physics sections
Unit marks for 2026-27
| Unit | Marks | Chapters assessed in the board exam | Priority |
|---|---|---|---|
| I. Chemical Substances: Nature and Behaviour | 25 | Chemical reactions and equations; acids, bases and salts; metals and non-metals; carbon and its compounds | Highest: equations and named reactions recur every year |
| II. World of Living | 25 | Life processes; control and coordination; how organisms reproduce; heredity (Mendel's laws, sex determination) | Highest: diagrams and process explanations |
| IV. Effects of Current | 13 | Electricity (Ohm's law, resistors in series and parallel, power); magnetic effects of current | High: numericals are reliable marks |
| III. Natural Phenomena | 12 | Light: mirrors, refraction, lenses; the human eye; prism, dispersion and scattering | High: ray diagrams and the lens and mirror formulas |
| V. Natural Resources | 5 | Our environment: ecosystems, ozone depletion, waste | Short: learn once, revise late |
Source: CBSE Class X Science (086) syllabus 2026-27. Total 80 marks plus 20 internal assessment.
Topics taught but not in the year-end exam
The 2026-27 syllabus says periodic classification of elements, evolution, and the electric motor, electromagnetic induction and generator are assessed only formatively in school. The teachers' note in the same document also lists heredity and evolution as not assessed in the year-end exam, while heredity appears in the assessed Unit II list. Ask your child's school how it is treating heredity, and check the 2026-27 sample paper.
Worked example 1 (chemistry): balancing an equation
Balance: Fe + H2O → Fe3O4 + H2 (iron reacting with steam).
- Start with the most complex formula, Fe3O4. It has 3 Fe and 4 O.
- Balance Fe: put 3 in front of Fe on the left.
- Balance O: 4 O atoms on the right means 4 H2O on the left.
- Balance H: 4 H2O gives 8 H atoms, so 4 H2 on the right.
- Answer: 3Fe + 4H2O → Fe3O4 + 4H2. Count again: Fe 3 = 3, O 4 = 4, H 8 = 8.
Worked example 2 (physics): image from a convex lens
An object is placed 30 cm in front of a convex lens of focal length 20 cm. Find the image position, magnification and power of the lens.
- Use the sign convention: u = -30 cm, f = +20 cm.
- Lens formula: 1/v - 1/u = 1/f, so 1/v = 1/20 + 1/(-30) = 3/60 - 2/60 = 1/60. v = +60 cm: a real image 60 cm behind the lens.
- Magnification m = v/u = 60/(-30) = -2: the image is inverted and twice the size.
- Power P = 1/f with f in metres = 1/0.20 = +5 dioptres.
Worked example 3 (physics): resistors in parallel
Resistors of 6 ohms, 6 ohms and 3 ohms are connected in parallel across a 3 V cell. Find the total resistance, current and power.
- 1/R = 1/6 + 1/6 + 1/3 = 1/6 + 1/6 + 2/6 = 4/6, so R = 6/4 = 1.5 ohms.
- Current from the cell: I = V/R = 3/1.5 = 2 A.
- Power: P = VI = 3 × 2 = 6 W.
- Sense check: the total resistance in parallel is always less than the smallest resistor (3 ohms), and 1.5 ohms is.
Common mistakes
- Writing word equations or unbalanced equations where a balanced chemical equation with state symbols is asked for.
- Ignoring the sign convention in the mirror and lens formulas, which flips the image from real to virtual.
- Unlabelled or wrongly labelled biology diagrams (the nephron, the human heart, the flower). Labels carry marks.
- Mixing up series and parallel formulas for resistance.
- Answering case-based questions from memory instead of from the data or passage given.
- Spending revision time on topics that are assessed only in school while weak board topics wait.
A revision order and how a tutor helps
Start with the two 25-mark units, because they are half the paper: chemical reactions and carbon compounds in chemistry, life processes and reproduction in biology. Then take electricity and light together, where numerical questions reward a fixed method. Leave the 5-mark environment unit for the final weeks. Finish with CBSE's 2026-27 sample paper and marking scheme under timed conditions; the paper is split into biology, chemistry and physics sections, so note which section loses most marks.
In one-to-one lessons a tutor runs short checks on each unit, then works on the specific weakness: balancing equations step by step, drawing ray diagrams to scale, or writing a biology answer that uses the keywords the marking scheme looks for. Many students are stronger in one science than the others, and the tutor can spend the lesson time where your child is losing marks.
Self-check
- Balance: Mg + O2 → MgO. (Answer: 2Mg + O2 → 2MgO)
- A concave mirror has focal length 15 cm. Is the image real or virtual for an object 10 cm away? (Answer: virtual, because the object is inside the focal length)
- Two 4 ohm resistors are in series with a 6 V battery. What current flows? (Answer: 0.75 A)
- Name the gas released when zinc reacts with dilute hydrochloric acid. (Answer: hydrogen)
- Draw and label a reflex arc from memory.
Common questions
Which units carry the most marks in CBSE Class 10 Science?
Chemical Substances and World of Living carry 25 marks each in the 2026-27 syllabus, which is 50 of the 80 board marks. Effects of Current carries 13, Natural Phenomena 12 and Natural Resources 5.
Is the periodic table chapter in the 2026-27 board exam?
No. The 2026-27 syllabus lists periodic classification of elements among the topics assessed only formatively in school, together with evolution and the motor and generator.
What types of questions are in the Science paper?
The syllabus lists very short answer and objective questions, assertion-reason, short and long answers, and source-based, case-based or passage-based questions. About a third of questions have an internal choice.
How is the internal assessment of 20 marks made up?
Periodic assessment 5 marks, multiple assessment 5, portfolio 5 and practical work 5, according to the 2026-27 syllabus.
What do LiveTutor science lessons cost?
Lessons are one to one, online and 60 minutes at $15 each, on a weekly plan of 1 to 5 lessons billed monthly. The first lesson is a free trial, so your child can start with the science they find hardest.
Sources
Dates and figures on this page come from these official and published sources. Always confirm deadlines on the official page before acting on them.