Measurement of Matter
Q1. Define matter.
A. Matter is anything that has mass and occupies space.
Q2. What is mass?
A. Mass is the amount of matter present in an object. It is constant everywhere in the universe.
Q3. State the SI unit of mass.
A. Kilogram (kg)
Q4. What is weight?
A. Weight is the force with which the Earth attracts an object towards itself. W = m Ć g
Q5. State the SI unit of weight.
A. Newton (N)
Q6. Define 1 newton.
A. 1 N is the force required to accelerate a mass of 1 kg at the rate of 1 m/sĀ².
Q7. What is volume?
A. Volume is the amount of space occupied by matter.
Q8. State the SI unit of volume.
A. Cubic metre (mĀ³)
Q9. What is density?
A. Density is the mass per unit volume of a substance. Formula: Ļ = m / V
Q10. State the SI unit of density.
A. Kilogram per cubic metre (kg/mĀ³)
Q11. Define relative density.
A. Relative density is the ratio of the density of a substance to the density of water at 4Ā°C.
Q12. Why is relative density a unitless quantity?
A. Because it is the ratio of two densities having the same unit, so the units cancel out.
Q13. What is the density of water at 4Ā°C?
A. 1000 kg/mĀ³
Q14. Name an instrument used to measure mass.
A. Physical balance or electronic balance.
Q15. How is volume of a regular solid measured?
A. By measuring its dimensions and using mathematical formulas.
Q16. How is volume of an irregular solid measured?
A. By the water displacement method using a measuring cylinder.
Q17. Why does a stone sink in water?
A. Because its density is greater than that of water.
Q18. Why does wood float on water?
A. Because its density is less than that of water.
Q19. What is the principle of Archimedes?
A. A body immersed in a fluid experiences an upward force equal to the weight of the fluid displaced by it.
Q20. State one application of Archimedesā principle.
A. It is used in designing ships and submarines.
Q21. What is buoyant force?
A. The upward force exerted by a fluid on an object immersed in it.
Q22. State the SI unit of buoyant force.
A. Newton (N)
Q23. Why does a balloon filled with helium rise in air?
A. Because the weight of the displaced air is greater than the weight of the balloon.
Q24. Why do divers wear weighted belts?
A. To counteract the buoyant force and help them stay underwater.
Q25. Define pressure.
A. Pressure is the force acting per unit area. P = F / A
Q26. State the SI unit of pressure.
A. Pascal (Pa)
Q27. Define 1 pascal.
A. 1 Pa is the pressure exerted when a force of 1 N acts on an area of 1 mĀ².
Q28. Why do nails have pointed tips?
A. To increase pressure by decreasing the area of contact, making it easier to penetrate.
Q29. Why is it easier to cut vegetables with a sharp knife?
A. Because the smaller area of the sharp edge increases pressure for the same force.
Q30. Why do camels have broad feet?
A. To reduce pressure on sand by increasing the surface area of contact.