States of Matter

 

 

Solids

Solids are substances which tend to be hard.

Solids cannot change their shape or volume.

Solids are very hard to squash because the particles are so close.

Liquids

 

Liquids are substances which can flow.

Liquids can change their shape but not their volume.

Liquid particles are close making liquids hard to squash.

Gases

 

Gases will fill any container they are put in.

Gases can change their shape and their volume.

Gases are easily squashed because the particles can be pushed closer together.

Diffusion

Because the particles in substances have energy they can move by themselves.

If we put orange juice and water together they will mix due to the movement of the particles.

If we open a bottle of perfume, the vapour will come out of the bottle and the gas particles will move all over the room, mixing with the air particles.

This mixing of particles is called diffusion.

Diffusion happens quickest in gases.

Expansion and Contraction

 

When we heat any substance, the particles get more energy and begin to move faster.

This movement causes the particles to move further apart so that the substance expands.

If we cool down a hot substance we take energy away from the particles.  They start to move more slowly and get closer together so the substance contracts.

All states of matter expand when heated and contract when cooled.

Gases expand most when heated and solids the least because gas particles are already far apart and are much freer to move.

Expansion and Contraction in Everyday Life

 

• Gaps are left between sections of railway line to allow expansion in summer
• Telephone wires are deliberately left loose to allow contraction in winter.
• Central heating systems have an expansion pipe to allow the heated water   to expand without bursting out the system

Gas Pressure

 

Gas particles are moving constantly and bumping into objects. 

Air pressure is caused by the particles of gas in the air bumping into things and so exerting a pressure.

An object such as a drinks can keeps its shape because the gas particles inside are balanced by the gas particles inside.  If we remove the particles inside using a vacuum pump then the pressure from the air outside collapses the can.

The effect of the pressure of gas can be seen using the Magdeburg Hemispheres.

They cannot be pulled apart when the gas is removed from inside because of the pressure of the gas particles outside.

 

 

 

 

 

 

Density

If we try to lift a cube of lead and an identically sized piece of aluminium we find the aluminium is much lighter than the lead.

Because the lead is heavier it must have more particles in it.  The particles must be packed together more closely.

A substance with a high density has a large mass in a small volume.

A substance with a low density has a small mass in a small volume.

The Water Cycle

 

Ice, water and steam are all the same substance – they are simply all in different states.

When the solid ice is heated the particles gain energy and eventually break away from each other forming water. 

When water is heated the particles gain more energy and eventually can separate from each other when steam is formed.

Cooling turns steam to water and further cooling turns water to ice.