Elements, Compounds and Mixtures Aim: To understand how matter is classified. At the end of this section you will be know about Element. Use of elements (4) Element symbols (1st 20 of periodic table) Common elements (also know) Cu, Ag, Zn, Al, Fe, Au other than 1st. 20) Compound + examples (4) Make compound = chemical reaction Mixture + examples (4) Exp. Iron and sulphur show difference between compound and mixture. Differences between compounds and mixtures (4)

Keywords

Some common elements

Mixtures, elements, compounds Scientists like to classify things. One way that scientists classify matter is by its composition. Ultimately, all matter can be classified as mixtures, elements and compounds.

Science teachers like talking about Particles Small pieces of something Particle is just a fancy name for individual things. These individual things could be atoms, molecules, lumps of soil, grains of sand, bits of metal. It doesn’t matter because particle is just a general word which is used when we don’t (or can’t) want to be exact about the type of things being described.

That’s why we talk about particles because it saves the bother of describing exactly what sort of things they are.

scientists can classify matter into: Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties. Solutions – a special kind of mixture where one substance dissolves in another. Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means. Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.

Elements An element is substance that cannot be broken down in a simpler substance by chemical means. There are more than 100 known elements and these are all listed on the periodic table.

Element Symbols and Compound Names An element is represented by a symbol (one or two letters 1st is always a capital) Examples: H (hydrogen) Ca (calcium) A compound is represented by a combination of symbols Examples: H2O (water) CO2 (carbon dioxide)

Element Symbols Some elements have symbols that come from their latin names e.g. Sodium is Na which comes from the latin name Natrium. The symbols for the elements are international and are the same for every element regardless of language or alphabet.

Symbols for the Common Elements on the Periodic Table

One Element The Same Element (Gas) (Solid) All the particles (atoms) are the same

A good example of when science teachers use the word particle is when talking about air. Air is a mixture of elements such as oxygen, argon and nitrogen mixed with compounds such as carbon dioxide

Some of the elements in air go around as single atoms (such as argon). Or as molecules such as oxygen. Compounds go around as molecules like Carbon Dioxide

Compounds and molecules A combination of atoms from different elements is a Compound Examples: water 2 hydrogens 1 oxygen The smallest complete unit of a compound that has the properties of that compound is a molecule.

A mixture of two elements Another element A mixture of two elements This one likes to go round in pairs as a gas (molecules)

What do we call these things? An Atom 3 Atoms

What do we call these things? 6 Atoms which happen to be of 3 different elements

What do we call these things? A Molecule Yes, it also happens to be 2 atoms joined together but we don’t call it “2 atoms joined together” we say it is one molecule

What do we call these things? A Molecule of a compound 2 molecules of a compound

This is not a mixture, it is a COMPOUND of two different elements This is just a mixture of two elements

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

Element, Compound or Mixture ?

A mixture of a compound and an element Element, Compound or Mixture ? A mixture of a compound and an element

Element vs.Compounds vs. mixtures Element compound mixture Single atom two different two or more Or group of atoms joined compounds Same atoms *heterogenous (looks diff.) *homogenous (same)

Showing the difference between a mixture and a compound Sulphur Iron sulphide a compound Iron metal

Iron and sulphur mixed Iron and sulphur mixed in the middle. You still see both elements. They can be separated easily using a magnet. Iron sulphide the compound cannot be separated using a magnet.

Making Iron Sulphide (FeS) a compound The glow of the chemical reaction between Iron and Sulphur to make Iron Sulphide. The Iron and Sulphur cannot be separated using a magnet.