Half-Yearly Class 8 Science Set 2

Syllabus: The half-yearly question paper is framed from the following chapters : Exploring the Investigative World of Science, The Invisible Living World: Beyond Our Naked Eye, Health: The Ultimate Treasure, Electricity: Magnetic and Heating Effects, Exploring Forces, Pressure, Winds, Storms, and Cyclones, Particulate Nature of Matter.

Section A 

Q1. Which scientist is known as the Father of Microbiology for being the first to clearly see and describe tiny living things like bacteria? (1 Mark)
(a) Robert Hooke
(b) Edward Jenner
(c) Hans Christian Oersted
(d) Antonie van Leeuwenhoek

Q2. When electric current flows through a conductor, it produces a magnetic field around it. This phenomenon is known as the (1 Mark)
(a) Heating effect of current
(b) Galvanic effect
(c) Magnetic effect of electric current
(d) Electrostatic force

Q3. Which hormone is responsible for prominent height increases during adolescence? (1 Mark)
(a) Insulin
(b) Sex hormones
(c) Adrenaline
(d) Growth hormone

Q4. What is the movement restriction of particles in the liquid state? (1 Mark)
(a) They cannot move at all.
(b) They are completely free to move in all directions.
(c) They are restricted to vibrations only.
(d) They move freely, but only within a limited space.

Q5. The force exerted by a charged body on another charged or uncharged body is known as (1 Mark)
(a) Magnetic force
(b) Muscular force
(c) Electrostatic force
(d) Gravitational force

Q6. What happens to the speed of an object thrown vertically upwards due to gravitational force? (1 Mark)
(a) It increases steadily.
(b) It decreases steadily until it stops momentarily.
(c) It remains constant.
(d) It immediately reverses direction.

Q7. What happens when two similarly charged objects are brought near each other? (1 Mark)
(a) They attract each other.
(b) They remain stationary.
(c) They acquire opposite charges.
(d) They repel each other.

Q8. What feature of a bacterial cell distinguishes it from cells of plants, animals, or fungi? (1 Mark)
(a) Presence of a cell wall
(b) Lack of cytoplasm
(c) Presence of a nucleoid instead of a well-defined nucleus
(d) They are all unicellular

Q9. Which type of force is friction? (1 Mark)
(a) Non-contact force
(b) Contact force
(c) Gravitational force
(d) Electrostatic force

Q10. What is the SI unit of pressure? (1 Mark)
(a) Newton (N)
(b) Kilogram (kg)
(c) Newton/metre² (N/m²)
(d) Joule (J)

Q11. The continuous process of warm air rising, cooling, and moisture condensing results in the formation of (1 Mark)
(a) Lightning
(b) Hail
(c) Clouds
(d) Cyclones

Q12. What is the minimum temperature at which a solid melts to become a liquid at atmospheric pressure? (1 Mark)
(a) Boiling point
(b) Sublimation point
(c) Melting point
(d) Freezing point

Q13. Which process helps recycle nutrients back to the soil? (1 Mark)
(a) Rusting
(b) Physical weathering
(c) Decomposition by microorganisms
(d) Galvanization

Q14. What property allows metals like copper to be drawn into wires? (1 Mark)
(a) Malleability
(b) Lustre
(c) Conductivity
(d) Ductility

Q15. Which household appliance utilizes the magnetic effect of electric current? (1 Mark)
(a) Electric heater
(b) Electric iron
(c) Water heater
(d) Electric motor (or electric bell/loudspeaker)

Section B

Q16. Explain why using a broad strap, rather than a narrow strap, makes carrying a heavy bag more comfortable. (2 Marks)

Q17. Describe the steps involved in dissolving a grain of potassium permanganate in a glass of water, illustrating the role of water particles. (2 Marks)

Q18. Explain the concept of the magnetic field of a current-carrying wire, referencing Oersted's observation. (2 Marks)

Q19. Differentiate between mass and weight of an object based on definition and change with location. (2 Marks)

Q20. Name the specific bacteria involved in curd formation and the condition necessary for its growth. (2 Marks)

Q21. Name two secondary sexual characteristics that appear in boys during adolescence. How are these changes caused? (2 Marks)

Q22. How does the Earth's magnetic field benefit life on Earth? (2 Marks)

Section C 

Q23. Describe the main components and function of the Nucleus, Cytoplasm, and Cell Membrane in a cell. (4 Marks)

Q24. Explain the concept of buoyance (upthrust). How does the relationship between gravitational force and buoyant force determine whether an object floats or sinks in a liquid? (4 Marks)

Q25. Describe the structure and internal components of a dry cell. Explain why dry cells are called 'dry' and why they are single-use. (4 Marks)

Q26. Describe the process by which yeast helps dough rise, and name another microorganism involved in food fermentation. (4 Marks)

Q27. Why are overhead water tanks placed at a height? Explain this phenomenon using principles of liquid pressure. (4 Marks)

Q28. Explain how the magnetic field of an electromagnet can be varied in strength and how its polarity can be reversed. (4 Marks)

Q29. What is the role of Rhizobium bacteria in the root nodules of leguminous plants? Why is this process important for soil health? (4 Marks)

Q30. Explain how the force of friction arises between two surfaces. Give two situations where friction is necessary or beneficial for motion. (4 Marks)

Q31. A wire of resistance 10 Ω is connected to a 5 V battery. Calculate the current flowing through the wire. Also, find the heat produced in 20 seconds. (4 Marks)

Section D

Q32. (a) Define health according to WHO. Discuss the three main aspects of well-being it encompasses. 
(b) List four healthy lifestyle habits recommended to maintain well-being. (5 Marks)

Q33. (a) Define an electromagnet and list two ways its strength can be increased.
(b) Describe how lifting electromagnets are used in industries. (5 Marks)

Q34. (a) Describe the process of curd formation, identifying the resulting substance that makes it sour.
(b) Name one unicellular fungus and one multicellular fungus. (5 Marks)