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Physics · Class 10 · Chapter 10: Properties of Matter

8 min

Key points

Matter exists in three states: solid, liquid and gas based on molecular arrangement and intermolecular forces
Density is the mass per unit volume of a substance and varies with temperature and pressure
Archimedes' principle states that upthrust equals the weight of displaced fluid
Surface tension is due to cohesive forces between liquid molecules at the surface
Viscosity is the property of fluids to resist flow due to internal friction between layers
Hooke's law states that extension is directly proportional to applied force within elastic limit
Young's modulus measures the stiffness of a solid material under tensile stress
Pascal's principle states that pressure applied to confined fluid is transmitted equally in all directions

Definitions

Density: The mass per unit volume of a substance is called density. Its SI unit is kg/m³.
Surface Tension: The property of liquid surface to behave like a stretched elastic membrane is called surface tension.
Viscosity: The property of a fluid by virtue of which it opposes the relative motion between its different layers is called viscosity.
Hooke's Law: Within elastic limit, the extension produced in a wire is directly proportional to the applied force.
Young's Modulus: The ratio of tensile stress to tensile strain within elastic limit is called Young's modulus.

Worked example

Define density. Calculate the density of a metal block having mass 150g and volume 50 cm³. (5 marks)

Density is defined as mass per unit volume of a substance. Formula: Density = Mass/Volume. Given: Mass = 150g, Volume = 50 cm³. Density = 150g ÷ 50 cm³ = 3 g/cm³. Therefore, the density of the metal block is 3 g/cm³.

Common mistakes

Students confuse density with specific gravity - remember density has units kg/m³
Always write Hooke's law as F ∝ x (within elastic limit) - don't forget the condition
In Archimedes' principle, upthrust equals weight of displaced fluid, not weight of the body
Surface tension acts along the surface, not perpendicular to it
Young's modulus formula: E = stress/strain, not strain/stress

Quick recap

Matter is anything that has mass and occupies space, existing in three states: solid, liquid, and gas. Physical properties can be observed without chemical change, while chemical properties involve reactions. Density equals mass divided by volume and is a characteristic property of substances. Particle theory explains that all matter consists of tiny particles in constant motion.

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