Matter in Our Surroundings — Quick Revision
Matter is made of very small particles that have space between them, are constantly moving and attract one another. Solids have a fixed shape and volume because the particles are tightly packed; liquids have a fixed volume but take the shape of the container; gases have neither fixed shape nor fixed volume and are highly compressible. Heating increases the kinetic energy of particles, so a solid melts at its melting point and a liquid boils at its boiling point; cooling reverses this. Sublimation is the direct change from solid to gas. Evaporation happens at all temperatures from the surface of a liquid and causes cooling because the particles that escape take energy with them.
Key Points
- •Matter is made of tiny moving particles with spaces between them
- •Solid: fixed shape + fixed volume
- •Liquid: fixed volume, shape of container
- •Gas: no fixed shape or volume, highly compressible
- •Melting point / boiling point: temperature of state change
- •Sublimation: solid → gas directly
- •Evaporation is a surface phenomenon and causes cooling