The particle nature of matter: revision

You should be familiar with the characteristic properties of solids, liquids and gases from your junior science classes and the work you did in Year 12 Chemistry.

Air freshener is released into one part of a room.

Within a short time the gas can be smelt throughout the room.

• Gas particles move quickly.

• Gas particles are able to diffuse through other gases (air is a gas).

Several pellets of dry ice (solid CO2) are put into an uninflated balloon which is then sealed.

As the dry ice turns into a gas, the balloon inflates.

• The particles in a gas are much further apart than they are in a solid.

A volumetric flask is filled up to the line with hot solution.

As the solution cools, the volume of the liquid decreases.

• Particles are further apart when they are hot than when they are cold.

Cold water

Hot water

Crystals of potassium permanganate are dropped into beakers of cold, and hot, water.

• Particles in a liquid are in constant motion. (Their motion is what spreads the particles of coloured crystal throughout the liquid.)

• The particles move more quickly when hot than cold.

50 mL of water, and 50 mL of ethanol are separately measured.

When the two liquids are combined they occupy a volume of less than 100 mL.

• There is empty space between particles in a liquid which other particles can occupy.

Attempt to compress sealed syringes containing a gas, and a liquid.

The gas compresses easily.

The liquid does not compress significantly.

• Particles in a gas are much further apart than they are in a liquid.

Molten wax is poured into a container.

When the wax sets we see that its volume has decreased.

• Particles in a liquid are a little further apart than they are in a solid.

Summary• Gas particles move quickly.• Gas particles are able to diffuse through other

gases• The particles in a gas are much further apart than

they are in a solid.• Particles are further apart when they are hot than

when they are cold.• Particles in a liquid are in constant motion.• The particles move more quickly when hot than

cold.• There is empty space between particles in a liquid

which other particles can occupy.• Particles in a gas are much further apart than they

are in a liquid.• Particles in a liquid are a little further apart than

they are in a solid.

These conclusions and the results of other, similar experiments lead us to a theory of matter known as

The particle nature of matter, or The kinetic theory of matter.

• Matter is made of particles (which may be molecules, ions or atoms), between which is empty space. There is little space between particles in solids and liquids and a large amount of space between particles of a gas.

• The particles in liquids and gases are in constant motion, while the particles in a solid stay in fixed positions but vibrate.

• The greater the temperature, the faster the particles move.

Particles in a solid are close together in fixed positions but can vibrate.

Particles in a liquid are close together but in constant motion

Particles in a gas are far apart and moving quickly.