How to Prepare for Practical Exams in Class 10 and 12 - Science and Other Subjects

Why Practical Exams Matter More Than You Think

Most students treat practical exams as an afterthought. They focus entirely on theory preparation and assume practicals will take care of themselves. This is a costly mistake.

For CBSE Class 12 Science students, practicals carry 30 marks in Physics, Chemistry, and Biology. That is 30 percent of your total marks in each subject. For Class 10, the practical/internal assessment component is 20 marks per subject.

Here is the math that should get your attention: a student who scores 60 out of 70 in theory but only 20 out of 30 in practicals gets 80 marks total. Another student who scores 55 out of 70 in theory but gets 28 out of 30 in practicals also gets 83 marks, a higher total despite knowing less theory.

Practicals are where you can secure marks with relatively less effort compared to theory. The experiments are fixed, the viva questions are predictable, and the marking is generally generous if you show genuine preparation.

CBSE Class 12 Science Practical Exam Format

Physics Practical (30 Marks)

The Physics practical exam is divided into:

Two experiments (one from each section): 8 marks each = 16 marks Practical record (experiments and activities): 6 marks Viva on experiments and activities: 5 marks Investigatory Project: 3 marks

Section A experiments typically cover optics (prism, lens) and electricity (meter bridge, potentiometer, galvanometer). Section B covers semiconductor devices (characteristic curves of diodes and transistors) and other experiments.

Important experiments to master:

Finding the value of v for different values of u in case of a concave mirror and finding the focal length. Finding the focal length of a convex lens by plotting graphs between u and v or between 1/u and 1/v. Determining resistance of a wire using meter bridge and hence finding the specific resistance. Verification of Ohm's law using voltmeter and ammeter. Finding the resistance and figure of merit of a galvanometer by half-deflection method. Determining the internal resistance of a cell using a potentiometer.

For each experiment, you should know: the aim, apparatus required, theory/formula, circuit diagram or ray diagram, procedure, observations table format, calculations, result, and precautions.

Chemistry Practical (30 Marks)

Volumetric Analysis (titration): 8 marks Salt Analysis (qualitative analysis): 8 marks Content-Based Experiment: 6 marks Class Record and Viva: 5 marks Investigatory Project: 3 marks

Titration experiments include:

Oxalic acid vs sodium hydroxide (acid-base titration) Mohr's salt vs potassium permanganate (redox titration)

For titrations, accuracy matters. Your titration readings should be concordant (within 0.1 to 0.2 mL of each other). Practice the technique of adding the titrant drop by drop near the endpoint.

Salt Analysis requires identifying the cation and anion in a given salt. The systematic procedure is:

Preliminary tests: Color, smell, flame test, dry heating Wet tests for anions: Dilute HCl group, concentrated H2SO4 group, independent group Wet tests for cations: Group reagent analysis (Group I through Group V) Confirmatory tests

Common salts tested: Zinc sulphate, Barium chloride, Ferrous ammonium sulphate, Copper sulphate, Aluminium chloride.

Biology Practical (30 Marks)

Experiments and spotting: 16 marks (one major experiment of 5 marks + one minor experiment of 4 marks + slide preparation of 5 marks + spotting of 7 marks) Practical Record + Viva: 7 marks Investigatory Project: 5 marks Class Record: 2 marks

Important experiments:

Preparing a temporary mount of onion peel to study mitosis. Study of plasmolysis in Rhoeo or lily epidermal peel. Study of pollen germination on a slide. Study of different stages of meiosis using permanent slides.

Spotting requires identifying specimens, slides, and models and writing 2 to 3 relevant points about each. Common spots include:

Flowers showing different types of pollination Specimens of organisms from different phyla Permanent slides of T.S. of ovary, testis, blastula Models of heart, kidney, brain

CBSE Class 10 Science Practical/Internal Assessment (20 Marks)

For Class 10, the internal assessment of 20 marks is divided into:

Periodic Assessment: 5 marks Subject Enrichment (Practical/Lab work): 5 marks Portfolio: 5 marks Multiple Assessments: 5 marks

The practical component (5 marks) is assessed internally by the school, but you should still prepare thoroughly because:

These marks are submitted to CBSE and count toward your final grade. The skills you learn help answer practical-based questions in the theory paper. Schools may conduct practical exams with external examiners in some cases.

Important Class 10 Science experiments:

Finding the pH of given samples using pH paper or universal indicator. Determining the focal length of a concave mirror and convex lens by obtaining the image of a distant object. Tracing the path of a ray of light through a glass slab. Studying the properties of acids and bases using indicators. Preparing a temporary mount of a leaf peel to show stomata. Studying binary fission in Amoeba and budding in yeast using permanent slides. Identification of different parts of an embryo of a dicot seed.

How to Prepare the Lab Record

The lab record (or practical file) carries 5 to 7 marks in most CBSE practical exams. Maintaining it properly throughout the year is essential.

For each experiment, your record should include:

Experiment number and date Aim of the experiment Materials/Apparatus required Theory (brief, 3 to 5 lines) Diagram (circuit diagram, ray diagram, or setup diagram) Procedure (step-by-step in numbered points) Observation table (neatly drawn with ruler) Calculations Result Precautions (at least 4 to 5 points)

Use a ruler for all lines and tables. Write in blue or black ink only. Diagrams should be in pencil.

The record should be complete, meaning every experiment listed in the CBSE syllabus should be present. Schools sometimes conduct only 10 out of 15 listed experiments, but your record should ideally cover all prescribed experiments.

Keep the record clean. Do not use correction fluid. If you make a mistake, draw a single line through it and write the correct text beside it.

Viva Voce Preparation

The viva carries 5 to 7 marks and is conducted by the external examiner alongside the practical exam. Most students fear the viva, but the questions are predictable.

Common Physics Viva Questions

What is the principle behind the meter bridge experiment? Why do we use a jockey and not a pointer on the bridge wire? What precautions should you take while using a galvanometer? What is least count? How do you calculate it for a vernier caliper or screw gauge? What happens to the focal length of a lens if it is dipped in water? Why do we take multiple readings in every experiment?

Common Chemistry Viva Questions

Why is the burette rinsed with the solution before filling it? What is the role of an indicator in a titration? Why must the flame test be performed with a clean platinum wire? What is the significance of concordant readings? What is a primary standard? Give examples. Why is dilute HCl preferred over dilute H2SO4 for salt analysis?

Common Biology Viva Questions

What stain is used for observing onion peel cells? Why? What is plasmolysis? How is it different from deplasmolysis? Name the stages of mitosis. Which stage is easiest to identify? What is the significance of pollen germination? How do you identify a monocot from a dicot by looking at a cross-section?

Prepare answers for at least 20 viva questions per subject. Keep your answers concise (2 to 3 sentences). The examiner does not expect essay-length responses.

Day-Before-Practical Preparation

Reread the procedure of the experiments most likely to be assigned. For Physics, review all circuit and ray diagrams. For Chemistry, review the salt analysis scheme and titration procedure. For Biology, review how to prepare slides and identify specimens.

Prepare your equipment: lab coat (if required), pen, pencil, eraser, ruler, lab record file, calculator, and any materials the school has asked you to bring.

Get a good night's sleep. Practical exams require hand-eye coordination and careful observation. Being tired leads to clumsy mistakes.

During the Practical Exam

Read the experiment instructions carefully before starting. Do not rush.

For Physics, set up the apparatus step by step. Take at least 5 to 6 readings for each experiment. Ensure your readings follow a trend (e.g., in a meter bridge experiment, the balance point should shift as you change the resistance).

For Chemistry, follow the systematic procedure for salt analysis. Do not jump to conclusions based on one test. Confirm every result with at least two tests.

For Biology, handle slides and specimens carefully. Use the microscope at the correct magnification. Label your drawings clearly with at least 8 to 10 labels.

Present your observations in a neat table format. Use a ruler to draw all tables.

During the viva, speak clearly and confidently. If you do not know an answer, say "I am not sure about this" rather than making something up. Examiners appreciate honesty.

Investigatory Project Tips

The investigatory project carries 3 to 5 marks. Choose a topic related to your syllabus and conduct a genuine investigation. Popular project topics include:

Physics: Study of earth's magnetic field using a tangent galvanometer, Study of interference patterns using soap films Chemistry: Study of presence of oxalate ions in guava fruit, Comparative study of the rate of fermentation Biology: Study of pollutants in a local water body, Investigating the effect of different fertilizers on plant growth

Your project report should include: title, objective, hypothesis, materials, procedure, observations, analysis, conclusion, and references. Include photographs of your experimental setup. A well-presented project with actual data (not copied from the internet) impresses examiners.

Making the Most of Practical Marks

Practicals are among the most controllable components of your board exam score. Unlike theory papers where question difficulty can vary, practical exams follow a predictable format with known experiments.

For structured revision before practicals, Padhaao can help you review experiment procedures, formulas, and viva questions interactively. Being able to quiz yourself on practical concepts strengthens your confidence for both the hands-on component and the viva.

Aim for 27 to 30 out of 30 in Class 12 practicals and 18 to 20 out of 20 in Class 10 internal assessment. These marks provide a comfortable cushion that reduces the pressure on your theory exams. A student who secures 28 in practicals needs only 62 out of 70 in theory for a 90 total. That changes the game entirely.