📘 Chapter 1: Matter in Our Surroundings

Matter

Anything that has mass and occupies space

Physical nature of matter

Matter is made up of particles

Evidence of particles in matter

Dissolving sugar/salt in water without level change

Small size of particles

One crystal of potassium permanganate can colour 1000 L water

Particles are very small

Beyond imagination — seen only with advanced tools

Particle motion

Particles are continuously moving

Kinetic energy

Energy due to motion of particles

Diffusion

Spontaneous intermixing of particles of different substances

Diffusion is faster in gases

Due to higher kinetic energy and more space

Temperature effect on diffusion

Increases with temperature

Particles attract each other

Force of attraction between particles holds matter together

Solid

Definite shape, volume, and high rigidity

Liquid

Fixed volume but not shape; fluid nature

Gas

No fixed shape or volume; compressible and fills container

Compressibility order

Gas > Liquid > Solid

Rigidity

Solid > Liquid > Gas

Inter-particle space

Solid < Liquid < Gas

Melting

Change from solid to liquid on heating

Boiling

Change from liquid to gas on heating

Melting point

Temperature at which a solid melts to liquid (ice: 273.15 K)

Latent heat

Heat required to change state without temperature change

Latent heat of fusion

Heat needed to convert solid into liquid

Latent heat of vaporisation

Heat needed to convert liquid into vapour

Sublimation

Direct conversion of solid to gas and vice versa

Examples of sublimation

Camphor, naphthalene

Evaporation

Surface phenomenon of liquid changing to gas

Factors affecting evaporation

Surface area, temperature, humidity, wind speed

Cooling effect of evaporation

Evaporation takes heat from surroundings

Why we sweat in summer

Evaporation of sweat cools the body

Why water kept in earthen pot is cool

Evaporation through pores cools water