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Particles and density (Kinetic theory (The kinetic theory states that…
Particles and density
Kinetic theory
The kinetic theory states that everything is made of tiny particles.
In solids, forces of attraction hold particles closely together.
the particles can vibrate but cannot move around.This explains why solids keep their shape and usually cannot be compressed.
In liquids, these particles are moving faster and so the forces of attraction between the particles are not strong enough to hold them in fixed positions.
The particles can move past each other so liquids flow and take the shape of their container.
the particles are still very close together, so liquids usually can't be compressed.
In a gas, the particles are far apart and moving around quickly.
gases are compressible and expand to fill their container.
When a substance changes state the particles end up in a different arrangement.
there are the same number of particles so the mass stays the same (mass is
conserved
).
This is a physical change, because no new substances are formed and the substance recovers its original properties if the change is reversed
Mass is also converted in chemical changes but the substances often cannot be reversed.
Density
The density of a substance is the mass of a certain volume the substance
Almost all substances are most dense when they are solids and least dense when they are gases.
the arrangement of particles can explain the differences in density between different states of matter.
a solid is usually denser than the same substance as a liquid, because the particles in the solid are close together.
Density can be calculated using
this equation
Density=mass/volume