CBSE Class 10 Science Practical Exam Guide 2027 — Experiments, Viva, and Full Marks Strategy

In short: The CBSE Class 10 Science practical exam carries 20 marks — split into Practical File (5 marks), Experiments (8 marks), Activities (2 marks), Project (3 marks), and Viva (2 marks). These 20 marks are arguably the easiest marks in your entire Class 10 exam because the experiments are known in advance, the viva questions follow predictable patterns, and the practical file is graded on completeness. Yet many students lose 3-5 marks due to poor preparation. This guide covers every experiment, the exact file format, common viva questions, and how examiners award marks.

Marks Breakdown — How the 20 Marks Are Distributed

This means:

• 5 marks are decided before the exam (practical file)
• 3 marks are decided before the exam (project)
• 12 marks are decided during the practical exam (experiments + activities + viva)

With proper preparation, scoring 18-20 out of 20 is achievable for every student.

Complete List of CBSE Class 10 Science Experiments

Physics Experiments

1. Verification of Ohm's Law

• Setup: Battery, ammeter, voltmeter, rheostat, resistance wire, key, connecting wires
• Procedure: Connect the circuit. Vary voltage using the rheostat. Record current for each voltage
• Observation: Tabulate V (voltage) and I (current). Plot V vs I graph — should be a straight line
• Calculation: Calculate R = V/I for each reading. Verify it is constant
• Common mistake: Connecting ammeter in parallel or voltmeter in series (should be ammeter in series, voltmeter in parallel)

2. Finding the Focal Length of a Concave Mirror

• Setup: Concave mirror, mirror stand, screen, scale, candle/object
• Procedure: Place the object at different distances. Adjust screen to get a sharp image. Record object distance (u) and image distance (v)
• Observation: Use mirror formula 1/v + 1/u = 1/f to calculate focal length
• Tip: Take at least 3 readings and find the average focal length

3. Finding the Focal Length of a Convex Lens

• Setup: Convex lens, lens stand, screen, scale, candle/object
• Procedure: Similar to concave mirror. Place object at different positions. Record u and v
• Observation: Use lens formula 1/v - 1/u = 1/f
• Common mistake: Sign convention errors — remember all distances measured from the optical centre

4. Tracing the Path of a Ray Through a Glass Slab

• Setup: Glass slab, drawing pins, white paper, protractor, scale
• Procedure: Fix two pins on one side of the slab. Look through the slab from the other side. Fix two more pins in line with the images. Remove the slab and join the pins to trace the ray path
• Observation: Measure angle of incidence, angle of refraction, and angle of emergence. Verify that the emergent ray is parallel to the incident ray (lateral displacement)

5. Tracing the Path of a Ray Through a Glass Prism

• Setup: Glass prism, drawing pins, white paper, protractor, scale
• Procedure: Similar pin-fixation method. Trace the incident ray, refracted ray inside the prism, and emergent ray
• Observation: Measure angle of incidence, angle of emergence, and angle of deviation

Chemistry Experiments

6. Finding the pH of Different Solutions

• Setup: pH paper/universal indicator, test tubes, various solutions (HCl, NaOH, lemon juice, tap water, salt water, etc.)
• Procedure: Dip pH paper in each solution. Compare colour change with the colour chart
• Observation: Record pH value for each solution. Classify as acidic (pH < 7), neutral (pH = 7), or basic (pH > 7)
• Key viva point: pH scale ranges from 0 to 14. Strong acids have low pH. Strong bases have high pH

7. Properties of Acids and Bases — Reaction with Metals

• Setup: Dilute HCl, dilute NaOH, zinc granules, test tubes, delivery tube
• Procedure: Add zinc to HCl. Collect the gas produced. Test with a burning matchstick
• Observation: A pop sound indicates hydrogen gas. Acids react with metals to produce hydrogen gas and a salt

8. Double Displacement Reaction

• Setup: Sodium sulphate solution, barium chloride solution, test tubes
• Procedure: Mix the two solutions in a test tube
• Observation: White precipitate of barium sulphate forms. This is a double displacement reaction: Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl

9. Properties of Acetic Acid (Ethanoic Acid)

• Setup: Ethanoic acid, litmus paper, sodium bicarbonate, water, test tubes
• Procedure: Test with litmus (turns blue litmus red). Add to NaHCO₃ (effervescence — CO₂). Dissolve in water (miscible)
• Observation: Ethanoic acid is a weak organic acid with a characteristic vinegar-like smell

10. Saponification Reaction (Making Soap)

• Setup: Vegetable oil, NaOH solution, common salt, beaker, glass rod
• Procedure: Heat oil + NaOH solution. Stir continuously. Add common salt to precipitate soap
• Observation: Soap forms as a solid that floats on the liquid surface
• Key viva point: Saponification is the hydrolysis of fat (ester) with a base to produce soap (sodium salt of fatty acid) and glycerol

Biology Experiments

11. Studying Binary Fission in Amoeba (Slide Observation)

• Setup: Prepared slide of Amoeba, microscope
• Procedure: Focus on the slide under low power, then high power
• Observation: Identify Amoeba showing stages of binary fission — nucleus divides first, then cytoplasm
• Drawing: Draw and label: cell membrane, nucleus, pseudopodia, dividing cell

12. Studying Budding in Yeast

• Setup: Yeast culture (prepared in sugar solution), glass slide, cover slip, microscope, methylene blue stain
• Procedure: Place a drop of yeast culture on a slide. Add methylene blue stain. Cover with cover slip. Observe under microscope
• Observation: Yeast cells showing buds at various stages of development
• Drawing: Draw and label: parent cell, bud, chain of buds (if visible)

13. Identifying Different Parts of an Embryo in a Dicot Seed

• Setup: Soaked gram or bean seeds, hand lens, dissection needle
• Procedure: Remove seed coat. Split the cotyledons. Identify embryonic parts
• Drawing: Draw and label: seed coat (testa), cotyledon, radicle (future root), plumule (future shoot), embryonic axis

14. Studying Homology and Analogy Using Specimens/Charts

• Setup: Charts or specimens showing homologous and analogous organs
• Observation: Homologous organs have similar structure but different functions (human arm, whale flipper, bat wing). Analogous organs have different structure but similar functions (bird wing, insect wing)
• Key viva point: Homologous organs indicate common ancestry (divergent evolution). Analogous organs indicate similar environmental pressures (convergent evolution)

Activities (Common in Practical Exam)

Activity 1: Testing the conductivity of different solutions using an LED/bulb circuit Activity 2: Demonstrating the phenomenon of refraction using a coin-in-water experiment Activity 3: Observing the stomata on a leaf peel under a microscope Activity 4: Studying the phenomenon of emulsification of fats Activity 5: Demonstrating CO₂ release during respiration using lime water

During the exam, you will be asked to perform 1 activity. Activities carry 2 marks and are simpler than full experiments.

Practical File Format

Your practical file should follow this format for each experiment:

Standard Format

EXPERIMENT [NUMBER]

AIM: [Statement of what you are trying to achieve/determine]

MATERIALS REQUIRED: [List of apparatus and chemicals]

THEORY: [Brief explanation of the underlying principle — 3-4 lines]

PROCEDURE: [Step-by-step instructions — numbered]

OBSERVATION TABLE:
[Tabulated readings with proper columns and headings]

CALCULATION: [If applicable — formulas and working]

RESULT: [What you found/concluded from the experiment]

PRECAUTIONS:
1. [Precaution 1]
2. [Precaution 2]
3. [Precaution 3]

File Scoring Criteria (5 marks)

Tips for full marks:

• Write every experiment the day it is performed in class. Do not leave it for later
• Draw diagrams for circuit setups and biological specimens
• Use pencil for diagrams and pen for text
• Write precautions for every experiment (examiners specifically check for this)
• Get each experiment signed by your teacher regularly

Viva Questions — Chapter-Wise Common Questions

The viva carries 2 marks. The external examiner asks 4-6 questions during or after the practical exam. Here are the most commonly asked questions:

Ohm's Law

• What is Ohm's Law? (V = IR)
• What is the unit of resistance? (Ohm, Ω)
• Why should the ammeter be connected in series? (To measure current flowing through the circuit)
• What happens to current if resistance increases? (Current decreases)

Light Experiments

• What is focal length? (Distance from the pole/optical centre to the focus)
• What is the sign convention used? (New Cartesian sign convention)
• What type of image does a convex lens form for an object at infinity? (Real, inverted, at the focus)
• What is lateral displacement? (The perpendicular distance between the incident ray and the emergent ray when light passes through a glass slab)

pH and Acids-Bases

• What is the pH of pure water? (7)
• What does a pH less than 7 indicate? (Acidic solution)
• Why does a strong acid have a low pH? (Higher concentration of H⁺ ions)
• What happens when an acid reacts with a base? (Neutralization — salt and water are formed)

Biology Experiments

• What is binary fission? (Division of a parent cell into two equal daughter cells)
• What is the advantage of budding? (Rapid reproduction without requiring a mate)
• What is the function of cotyledons? (Store food for the developing embryo)
• Difference between homologous and analogous organs?

For detailed viva preparation across all subjects, see the CBSE practical exam viva tips guide.

Day of the Practical Exam — What to Expect

Before You Enter

• Carry your practical file (signed by teacher)
• Carry your project file
• Bring a pencil, pen, scale, and eraser
• Reach 30 minutes early

During the Exam

1. You will be assigned experiments — typically 2 experiments + 1 activity from the prescribed list
2. Perform the experiment — set up apparatus, take readings, record observations
3. Write the experiment in the answer sheet provided (not in your practical file)
4. The viva may happen during or after the experiment
5. Submit the answer sheet and show your practical file to the examiner

How Examiners Award Marks

For each experiment (4 marks each):

• Setting up apparatus correctly: 1 mark
• Performing the experiment with correct procedure: 1 mark
• Recording observations/readings accurately: 1 mark
• Calculating results and writing conclusion: 1 mark

For the activity (2 marks):

• Correct setup and performance: 1 mark
• Correct observation and conclusion: 1 mark

Common Reasons Students Lose Marks

1. Not recording readings in a table format — always use a proper observation table
2. Not writing precautions — examiners specifically check for precautions
3. Messy diagrams — draw neat, labelled diagrams for every experimental setup
4. Wrong units — writing voltage without "V" or current without "A"
5. Incomplete practical file — missing even 2-3 experiments costs marks
6. Unable to answer viva questions — prepare the theory behind each experiment

Project Work (3 marks)

The Science project is evaluated on:

• Topic relevance (1 mark) — is the topic related to the Class 10 syllabus?
• Content and presentation (1 mark) — quality of research, diagrams, data
• Conclusion and originality (1 mark) — did you draw meaningful conclusions?

Good project topics:

• Water quality testing in your locality
• Effect of different fertilizers on plant growth
• Study of pH of different soaps and detergents
• Solar energy applications in daily life
• Comparing the cleaning capacity of different brands of soap

Submit the project on time. A late submission may be penalized.

Frequently Asked Questions

Can I score 20/20 in Science practicals?

Yes. The majority of students who prepare the practical file, practice the experiments, and study the viva questions score 18-20 marks. The practical exam is designed to be achievable — it tests basic lab skills, not advanced research ability.

What if I make a mistake during the experiment?

Tell the examiner honestly and ask to redo the step. Examiners appreciate honesty. If your readings are slightly off, note them in the observation table and mention possible sources of error. This shows scientific thinking and does not lose marks.

How many experiments should I prepare for the practical exam?

Prepare all experiments from the prescribed list. The examiner selects experiments on the spot. You cannot predict which ones will be assigned. However, Physics experiments (Ohm's law, focal length) and Chemistry experiments (pH, reactions) are most commonly chosen.

Is the practical exam conducted by my school teacher or an external examiner?

CBSE practical exams have both an internal examiner (your school teacher) and an external examiner (teacher from another school). The external examiner ensures standardized evaluation and conducts the viva.

When are the practical exams held?

CBSE practical exams are typically held in January-February, before the theory exams in March. Your school will announce the exact dates. Results are combined with theory exam results in the final marksheet.

What if my practical file is incomplete?

An incomplete practical file loses marks in the file evaluation (out of 5 marks). More importantly, the practical file is evidence that you performed the experiments during the year. Complete it as soon as possible — even if experiments were done months ago, write them up neatly from your notes or textbook.

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