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6
Physical and Chemical Changes
• A physical change involves the change of state of a substance and produces no new substance, e.g.
melting of ice or boiling of water.
• A chemical change is when two or more substances react together to form a new compound with
different properties. Chemical changes occur on an atomic level, e.g. combustion, decomposition,
neutralization.
Kinetic Particle Theory
The Kinetic Particle theory of matter states that matter consists of microscopic particles , atoms at
the smallest level , in constant random motion (brownian motion )
Solids :
Fixed volume
Fixed shape
Atoms vibrate in position
Regular, fixed arrangement
Particles are tightly packed together
Generally more dense than liquids and gases
Liquids :
Fixed Volume
Adapt to the shape of container
Slightly compressible
Particles move and slide past one another
Generally less dense than solids but more than gases
Gases :
No fixed volume
Take shape of container and fill it
Very low density