The states of matter

Chapter 8The states of matter

What is matter?Any thing around us that has:Mass(Amount of material in a substance)

Volume(Amount of space and object takes)

Examples for matter:1)Solid2)Liquid3)Gas

A solid:Has definite mass.Definite shape.It does not flow and it is hard to be compressed it

A liquid:Has a definite mass.Its volume does not change .Its hard to be compressed but it flows easily.The shape of the liquid changes as it takes the shape of the container holding it.

A gas:Has a definite mass.Its volume vary and it takes the shape of the container holding it.It flows easily and it can be compressed.

Select one state of matter and imagine that it has been removed from the world.List things that could not exist if it is absent.

2000 years ago a Greek thinker named Democritus said that the smallest particle that cannot be divided is called an AtomThe word Atom means: Indivisible.

The particle theory of matterIt stated that matter is made from particles.The particles are so tiny that they cannot be seen by naked eyes.Different substances are made from different particles have different sizes.The particles are atoms and molecules.

Elements:Either made of one kind of atom called : Molecule.Example 1:Oxygen

Example 2:Hydrogen

Or different kinds of atoms called :CompoundExample: Water

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The particles in solidsThere is a strong forces hold the particles together in 3-dimensional structure.In many solids, the particles form an arrangement called lattice.The particles in all solids just vibrate in its own position.

The particles in liquids:

Why do liquids flow but solids do not?The forces that hold the particles together are weaker than in solids.The particles in a liquid can change position by sliding over each other.

The particles in gases:The forces of attraction between the particles are very weak and the particles can move away from each others in all directions.When they hit each others or the wall of the container they bounce and change their direction.

Physical change:It is a reversible kind of change in state of matter by heating or cooling.

MeltingWhen a solid is heated it loses its shape and starts to flow.The temperature at which melting takes place is called : Melting point

Examples:

The particle theory:When a solid is heated , the heat provides the particles with more energy.The energy makes the particles vibrate strongly and push each other and the solid expand.If the solid is heated more the energy makes the particles vibrate more strongly and this causes the particles to slide over each other and become a liquid.

N.B : During the time from solid starts to melt until it completely change to liquid, its temperature does not increase .All the heat energy is used to separate the particles so that they can flow over one another.

FreezingIt is the reverse of melting.It is the change from liquid to solid .The temperature at which this takes place is called: Freezing point.

- when the particles are cooled down they lose energy so they cannot slide over each others . They start to vibrate in their own position in the lattice .The liquid become a solid.

Evaporation

When the liquid is heated the particles start to gain heat and move faster leading to the gas escaping from the surface of the liquid.

BoilingWhen a liquid reaches a certain temperature, it forms a gas inside it . The gas makes bubbles, which rise to the surface and burst into the air . This is called boilingThe temperature at which this takes place is called : Boiling point.If the boiling liquid is heated more strongly, its temperature does not rise but it boils more quickly.

Graph for boiling point of a liquid

Particle theory for boilingWhen a liquid is heated, all the particles receive more energy and move quickly. The fastest moving particles escape from the liquid surface and form gas.

CondensationResults as cooling down of gas to change to liquid.

The particle theory for condensationThe particles losses energy when they are cooled so they can no longer bounce off each other when they meet.The particles now slide over each other and form a liquid.

SublimationA few substances can change from a solid to gas , or from gas to solid directly.Example: solid carbon dioxide (dry ice).

Change between states of matter

Dissolving

Copper sulfate dissolves in water to form cear blue solution

When substance dissolves in a liquid it forms solution.The liquid is called solvent and the solid that dissolves in it is called solute.

The particle theory for dissolvingThere are small gaps between the particles in a liquid. When a substance dissolves in a liquid, its particles spread out and fill the gaps.