Mixtures and Pure Substances

Heterogeneous or homogeneous?

We found out in the lab that they were all Heterogeneous (even

though some looked homogeneous)

So is everythingheterogeneous?

Isn’t anythinghomogeneous?

Experiment – add kool-aid to water

We added two different materials!

• Can this mixture be classified as heterogeneous?

• No, because after we’ve finished mixing it together we can see only one part. It has only one set of properties.

• We call this homogeneous mixture a solution

A homogeneous mixture or solution is a mixture that appears the same all over -- the different materials are not visible.

• The parts of a solution will not ‘settle out’ (like fat in

milk)

• Solutions can be solids, liquids, or gases

Some examples of common solutions:

Solid solution:Tooth filling: silver + tin + mercury

Gas solution:Air: Nitrogen + Oxygen + other gases

Liquid solution:Ocean/Seawater: salt + water

A mechanical mixture is a mixture in which the different parts can be seen easily with the unaided eye.

• When materials are mixed together but we can still see the different parts we call it a mechanical mixture

Heterogeneous materials - can see two parts

Mechanical Mixtures

Matter

Homogeneous materials can see only one

thing - one set of properties

Homogeneous mixtures

(solutions)They’re mixed together so well you only see one thing – it looks pure

but it isn’t

But what aboutpure things?

Isn’t anythingreally pure?

Or is everything just mixed together so well we can’t see the parts?

Solutions

PURE THINGS

• Yes, pure things exist too!

• The properties of various mixtures and substances are explained by the particle theory of matter:- all matter is made up of extremely small particles- each pure substance has its own kind of particle (atoms or molecules), different from the particles of other pure substances.

• A pure substance is any material made up of only one kind of extremely small particle (either an atom or a molecule).

• A pure substance:- is always homogeneous- has the same properties no matter where in the world it is found.

Heterogeneous materials - can see two parts

Mechanical Mixtures

Matter

Homogeneous materials can see only one

thing - one set of properties

Homogeneous mixtures

(solutions)They’re mixed together so well you only see one thing – it looks pure

but it isn’t

Pure substancesYou can only see one thing because there is only one kind of particle in

it.