In short: The Class 10 Science practical exam carries 20 marks and is often the easiest place to score full marks — yet many students lose 3-5 marks due to poor viva preparation or incomplete lab records. This guide covers all CBSE prescribed experiments across Physics, Chemistry, and Biology, the exact marks distribution, common viva questions with concise answers, lab record format, and exam day do's and don'ts. Most state boards follow a similar practical structure, so this applies broadly.
Marks Distribution — CBSE Class 10 Science Practical
| Component | Marks | Details |
|---|---|---|
| Experiments (2 from each section) | 8 | 2 from Physics + Chemistry list, 2 from Biology list |
| Practical-Based Questions | 4 | Written questions based on practical skills |
| Activities Record | 2 | Year-long activity record file |
| Investigatory Project / Portfolio | 3 | One project on any Science topic |
| Viva | 3 | Oral questions by external/internal examiner |
| Total | 20 |
Complete List of Experiments
Physics Experiments
| # | Experiment | Key Concept |
|---|---|---|
| 1 | Finding focal length of a concave mirror by obtaining image of distant object | f = R/2 |
| 2 | Finding focal length of a convex lens by obtaining image of distant object | Parallel rays converge at focus |
| 3 | Tracing the path of a ray of light through a glass slab | Lateral displacement, Snell's law |
| 4 | Tracing the path of rays through a glass prism | Dispersion, deviation angle |
| 5 | Image formation by a convex lens for different positions of object | u-v method, lens formula |
| 6 | Determining equivalent resistance of resistors in series | R = R₁ + R₂ + R₃ |
| 7 | Determining equivalent resistance of resistors in parallel | 1/R = 1/R₁ + 1/R₂ + 1/R₃ |
| 8 | Verifying Ohm's Law | V-I graph is a straight line |
Chemistry Experiments
| # | Experiment | Key Concept |
|---|---|---|
| 1 | Finding pH of different solutions using pH paper/universal indicator | pH scale 0-14 |
| 2 | Studying properties of acids and bases with indicators | Litmus, phenolphthalein, methyl orange |
| 3 | Performing and classifying chemical reactions | Combination, decomposition, displacement, double displacement |
| 4 | Observing reaction of zinc, iron, copper, aluminium with HCl and NaOH | Activity series |
| 5 | Studying reactions of sodium sulphate with barium chloride | Double displacement, precipitation |
| 6 | Observing decomposition of ferrous sulphate | Thermal decomposition |
Biology Experiments
| # | Experiment | Key Concept |
|---|---|---|
| 1 | Preparing temporary mount of a leaf peel to show stomata | Guard cells, transpiration |
| 2 | Observing binary fission in Amoeba and budding in yeast | Asexual reproduction |
| 3 | Identifying parts of an embryo of a dicot seed (gram, pea) | Radicle, plumule, cotyledons |
| 4 | Studying the comparative cleaning capacity of soap in hard and soft water | Scum formation, effect of CaCl₂ |
| 5 | Studying homology and analogy with charts/models | Evolution evidence |
| 6 | Identifying different adaptations in animals with charts | Adaptation types |
Practice any chapter on Padhaao
AI tutor for CBSE, ICSE & 15 state boards · 10 learning modes · 3 free chapters daily
How Experiments Are Conducted on Exam Day
Typical Exam Flow:
- Reporting (30 min before) — Check your roll number, seating, apparatus
- Experiment selection — Examiner assigns 1-2 experiments (you usually get a slip/chit)
- Performing experiments (45-60 min) — Set up, perform, record observations
- Writing observations — Neatly record in provided answer sheet
- Practical-based questions (15-20 min) — Written questions based on experiments
- Viva (5-10 min) — External examiner asks oral questions
Important: You don't choose your experiments. The examiner assigns them. So prepare ALL experiments.
Top 30 Viva Questions with Answers
Physics Viva Questions:
Q1: What is the focal length of a concave mirror? The distance between the pole (P) and the principal focus (F). For a concave mirror, f = R/2 where R is the radius of curvature.
Q2: Why do we use a distant object to find the focal length? Rays from a distant object are practically parallel. Parallel rays converge at the principal focus after reflection/refraction, making it easy to locate the focus.
Q3: What is Ohm's Law? At constant temperature, the current through a conductor is directly proportional to the potential difference across it. V = IR.
Q4: What happens if resistors are connected in series vs parallel? In series: total resistance increases (R = R₁+R₂). In parallel: total resistance decreases (1/R = 1/R₁+1/R₂). Same current flows through series; same voltage across parallel.
Q5: What is lateral displacement in a glass slab experiment? The perpendicular distance between the incident ray and the emergent ray after passing through a glass slab. The emergent ray is parallel to the incident ray but shifted sideways.
Q6: Why does a glass prism cause dispersion of white light? Different colours (wavelengths) of white light have different refractive indices in glass. Violet bends the most (highest refractive index) and red bends the least.
Q7: What is the SI unit of resistance? Ohm (Ω). Named after Georg Simon Ohm.
Q8: Why do we take multiple readings in experiments? To minimize random errors and improve accuracy. The mean of multiple readings is closer to the true value.
Q9: What is the difference between a real and virtual image? Real images are formed when rays actually converge (can be caught on screen). Virtual images are formed when rays appear to diverge from a point (cannot be caught on screen).
Q10: What type of mirror is used in vehicles as rear-view? Convex mirror — because it provides a wider field of view and always forms an erect, diminished, virtual image.
Chemistry Viva Questions:
Q11: What is pH? What does a pH of 7 mean? pH is a measure of hydrogen ion concentration. pH 7 means the solution is neutral (neither acidic nor basic), like pure water.
Q12: Name two natural indicators. Litmus (from lichen) and turmeric (haldi). Red cabbage juice also works as a natural indicator.
Q13: What happens when zinc reacts with dilute HCl? Zinc displaces hydrogen: Zn + 2HCl → ZnCl₂ + H₂↑. Hydrogen gas is produced (pops with a burning matchstick).
Q14: Why does copper not react with dilute HCl? Copper is below hydrogen in the activity series — it cannot displace hydrogen from acids.
Q15: What is a precipitation reaction? Give an example. A reaction where two aqueous solutions react to form an insoluble solid (precipitate). Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl. White precipitate of BaSO₄ forms.
Q16: What colour change indicates decomposition of ferrous sulphate? Green crystals of FeSO₄ turn to reddish-brown (Fe₂O₃) on strong heating. SO₂ and SO₃ gases are released.
Q17: Why should you not taste chemicals in the lab? Safety reason — chemicals can be toxic, corrosive, or harmful. We identify substances by their physical properties (colour, smell at a distance) and chemical tests.
Q18: What is a double displacement reaction? A reaction where ions of two compounds exchange partners. AB + CD → AD + CB.
Q19: Why is pH important in everyday life? Our stomach needs pH 1-2 for digestion. Tooth enamel corrodes below pH 5.5. Soil pH affects crop growth. Acid rain has pH below 5.6.
Q20: What is universal indicator? A mixture of several indicators that gives a range of colours for different pH values (red for acidic, green for neutral, blue/purple for basic).
Biology Viva Questions:
Q21: What are stomata? What is their function? Stomata are tiny pores on leaf surface, surrounded by guard cells. They regulate gas exchange (CO₂ in, O₂ out) and transpiration (water loss).
Q22: What is binary fission? Name an organism that shows it. Binary fission is a type of asexual reproduction where the parent cell divides into two equal daughter cells. Amoeba reproduces by binary fission.
Q23: What is the difference between budding and binary fission? In binary fission, the parent splits into two equal parts. In budding, a small bud grows on the parent, which detaches to form a new organism (e.g., yeast, Hydra).
Q24: What are cotyledons? Cotyledons are the seed leaves (food-storing structures) in the embryo of a seed. Dicot seeds have two cotyledons, monocot seeds have one.
Q25: Why does soap not lather well in hard water? Hard water contains Ca²⁺ and Mg²⁺ ions. Soap reacts with these to form insoluble scum (calcium/magnesium stearate), reducing lathering.
Q26: What is homology? Give an example. Organs with similar basic structure but different functions — indicates common ancestry. Example: forelimbs of human (grasping), whale (swimming), bat (flying).
Q27: What is the difference between homologous and analogous organs? Homologous: same structure, different function (evolutionary origin). Analogous: different structure, same function (convergent evolution). Example of analogous: wings of bird and insect.
Q28: What causes guard cells to open and close stomata? When guard cells become turgid (absorb water), stomata open. When guard cells lose water (become flaccid), stomata close. This is controlled by K⁺ ion concentration.
Q29: Name the parts of a dicot seed embryo. Radicle (develops into root), plumule (develops into shoot), cotyledons (food storage), and seed coat (protection).
Q30: Why is yeast used in bread making? Yeast performs anaerobic respiration (fermentation), producing CO₂ gas which makes the dough rise, making bread soft and fluffy.
Lab Record Format
How to Maintain Your Lab Record:
| Section | What to Write |
|---|---|
| Date | Date of experiment |
| Experiment No. | Serial number |
| Aim | One-line purpose |
| Materials Required | List of apparatus and chemicals |
| Theory | Brief concept (3-4 lines) |
| Procedure | Step-by-step numbered list |
| Observation Table | Neatly ruled table with readings |
| Calculation (if any) | Formula + substitution + answer |
| Result | One-line conclusion |
| Precautions | 3-4 bullet points |
| Diagram | Labeled setup diagram |
Lab Record Tips:
- Use ruled pages — neatly written
- Blue pen for text, pencil for diagrams
- Tables should be ruler-drawn — not freehand
- Get each experiment signed by teacher after completion
- Don't leave experiments incomplete — 2 marks depend on the record
Exam Day Do's and Don'ts
Do's:
- ✅ Reach 30 minutes early — check apparatus
- ✅ Carry your own geometry box (ruler, pencil, eraser)
- ✅ Read the experiment slip carefully before starting
- ✅ Set up apparatus neatly — examiner observes your method
- ✅ Take at least 3 readings for each experiment
- ✅ Write observations in the provided answer sheet — neat and tabulated
- ✅ Draw diagrams for every experiment
- ✅ During viva, speak clearly and confidently
- ✅ Say "I'm not sure" if you don't know — don't guess wildly
- ✅ Carry your lab record — it will be checked
Don'ts:
- ❌ Don't panic if you get an unfamiliar experiment — the examiner will guide you
- ❌ Don't touch chemicals with bare hands
- ❌ Don't rush through the experiment — accuracy matters more than speed
- ❌ Don't fabricate readings — examiners can tell
- ❌ Don't argue with the examiner during viva
- ❌ Don't forget to write precautions — 0.5-1 mark easy
- ❌ Don't leave your workspace messy — clean up after experiment
Frequently Asked Questions
Can we choose which experiment to perform?
No. The examiner assigns experiments through a chit/slip system. You may get any combination of Physics + Chemistry or Biology experiments. That's why you must prepare all experiments.
What if the experiment gives wrong results?
Write your actual observations honestly. In the result section, mention what the expected result should be and possible sources of error. Examiners give marks for correct procedure and honest reporting, not just correct results.
How long is the practical exam?
Typically 2-3 hours including experiment performance, written questions, and viva. The viva is usually 5-10 minutes per student. Some boards conduct it over multiple days.
Is the lab record checked during the practical exam?
Yes. The examiner reviews your lab record (maintained throughout the year) and assigns marks based on completeness, neatness, and regularity. Missing experiments or unsigned records lead to mark deductions.
How important is the viva? Can I score without it?
The viva carries 3 marks out of 20. While you can score well in experiments and record, losing all 3 viva marks is avoidable. Prepare the top 20-30 questions — most viva questions are basic and repeat every year.
Padhaao Can Help You Prepare
Practice viva questions, understand experiment concepts, and get step-by-step experiment explanations on Padhaao. AI tutor explains the "why" behind every experiment — not just the procedure.
₹21/mo (annual plan)
Padhaao covers 17,000+ chapters across 17 boards
Your exact syllabus. 10 learning modes. 3 free daily. Pro for unlimited - ₹21/month (annual plan).
Want the full chapter with solved examples?
10 learning modes. Board-specific content. 3 free chapters every day.
Try it free