Tamil Nadu Class 8 Science Model Paper 2 — Samacheer Kalvi

Instructions

• Time: 2 hours 30 minutes
• Maximum Marks: 75
• Answer all questions in Section A; follow instructions in Sections B and C.

Section A — One Mark Questions (15 × 1 = 15 marks)

1. What is the SI unit of force? 2. Define pressure. 3. What is the valency of carbon? 4. Convert 0°C to Kelvin. 5. State Ohm's law in one sentence. 6. Name the type of mirror used in a solar cooker. 7. What is the modern periodic law? 8. Define pH. 9. Name the green pigment in leaves. 10. What is transpiration? 11. Which organ secretes bile? 12. Name the microorganism used to make curd. 13. Define pollination. 14. What is sublimation? Give one example. 15. Name one vaccine-preventable disease.

Section B — Short Answer (5 × 3 = 15 marks)

Answer any five of the following.

16. Distinguish between scalar and vector quantities with two examples each. 17. Explain convection with one experiment and one daily-life example. 18. Explain series and parallel circuits. Give the formulae for total resistance in each. 19. Describe the modern periodic table. How is it different from Mendeleev's periodic table? 20. Explain the properties of acids and bases with two examples each. 21. Describe the transportation of water and food in plants. Name the tissues involved. 22. Explain the concept of immunity. Distinguish between innate and acquired immunity.

Section C — Long Answer (5 × 9 = 45 marks)

Answer all questions. Each question has internal choice.

23. (a) Explain the working of a screw gauge. How is the final reading calculated? Include a neat diagram. OR (b) Explain the periodic classification of elements. State Mendeleev's contributions and the limitations of his table.

24. (a) Describe the structure and function of the human heart. Explain pulmonary and systemic circulation. OR (b) Explain the types of hydrocarbons — alkanes, alkenes, and alkynes — with formulae and examples. Write two uses of organic compounds.

25. (a) State and explain the laws of reflection. Distinguish between concave and convex mirrors with their uses. OR (b) Classify microorganisms into five types. Give characteristics, examples, and one use or harm for each type.

26. (a) Explain the heating effect of electric current. Write Joule's law. Give four applications. OR (b) Explain sexual reproduction in flowering plants. Include pollination, fertilisation, and fruit/seed formation.

27. (a) Explain common salt, washing soda, baking soda, and bleaching powder — their formulas, preparation, and uses. OR (b) Explain puberty in boys and girls. Why is puberty a normal biological process?

Time Plan for This Paper

• First 10 minutes: Read all questions carefully.
• Section A: 20 minutes.
• Section B (five questions): 30 minutes.
• Section C (five questions): 60 minutes.
• Final 10 minutes: Verify units, equations, diagrams, and completeness.

Correction Plan

After writing this paper, classify each lost mark:

• Conceptual error — revise the chapter.
• Missing keyword — practise writing definitions.
• Diagram error — redraw the diagram three times.
• Calculation error — redo the numerical slowly.