Practical Exam Tips for Science Subjects — ICSE & CBSE Guide

Importance of Practicals in Board Marks

• CBSE Class 12: 30 marks practical per science subject; ICSE Class 10: 20 marks practical
• Practical marks are internal and largely depend on school teacher + project file quality
• External examiner + internal teacher evaluate during practical exam for CBSE Class 12

Maintaining the Record/Journal File

• Complete all experiments; write date, aim, materials, procedure, observation, result, precautions
• Observations must match real lab results, not textbook values exactly; small variation is natural
• Diagrams: pencil; labelled neatly; proportionate; use ruler for straight lines

Physics Practical Tips

• Parallax error: eye must be level with reading; always mention how to avoid it
• Ohm's law experiment: plot V-I graph; slope = resistance; ensure graph passes near origin
• Metre bridge/Wheatstone: understand balancing length concept; can be asked in viva

Chemistry Practical Tips

• Salt analysis: follow systematic procedure; don't skip steps; record smell, colour, solubility
• Titration: rinse burette with KMnO₄/Na₂S₂O₃ before filling; use 3 concordant readings
• Chromatography: measure Rf values accurately; label spots; run solvent in correct direction

Biology Practical Tips

• Microscope handling: carry with both hands; clean lenses with soft cloth before use
• Permanent slides: identify correctly; state stain used (e.g., safranine for xylem)
• Dissection (ICSE): follow diagram instructions; preserve specimen properly; label diagram of observation

Viva Preparation

• Common viva questions: purpose of each reagent, sources of error, theory behind observation
• Practice explaining procedure in your own words without reading from journal
• Be honest if you don't know; say 'I'm not sure, but I think it is…' rather than guessing confidently and wrongly

Scoring Full Marks in Practicals

• Journal file: 100% complete, neat, accurate — this is 30% of practical marks
• Conduct experiment confidently; don't rush; ask supervisor if genuinely confused about procedure
• Aim, result and precautions section: examiner checks these first; must be precise and accurate