Classifying Matter: Elements, Compounds, and Mixtures

Classifying Matter:Elements, Compounds, and Mixtures Charbonneau 2012

Pure Substances • A sample of matter that has definite chemical and physical properties. Atoms Elements Compounds Molecules

Elements • pure substance that cannot be separated into simpler substance by physical or chemical means.

Compounds Pure substance composed of two or more different elements joined by chemical bonds. • Made of elements in a specific ratio that is always the same • Has a chemical formula • Can only be separated by chemical means, not physically H2O NaCl CO2

Mixtures • A combination of two or more pure substances that are not chemically combined. • substances held together by physical forces, not chemical • No color, gas or heat change takes place • Each item retains its properties in the mixture • They can be separated physically Chem4kids.com

One Element The Same Element (Gas) (Solid)

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

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

Element, Compound or Mixture ? Mixture

Element, Compound or Mixture ? Compound

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

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

What about when all the atoms are stuck together like in a solid element?

This is just a load of atoms in a solid element, it is not a big molecule

Finally, just to confuse you even more, science teachers like talking about Particles 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.

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.

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

Can you identify the following? You will be shown a series of photos. Tell if each photo represents an item composed of an element, compound, or mixture. Review: • An element contains just one type of atom. • A compound contains two or more different atoms joined together. • A mixture contains two or more different substances that are only physically joined together, not chemically. • A mixture can contain both elements and compounds.

Element, Compound, or Mixture? Rocks

Element, Compound, or Mixture? Copper

Element, Compound, or Mixture? Cu Copper

Element, Compound, or Mixture? Jelly Beans

Element, Compound, or Mixture? Table Sugar

Element, Compound, or Mixture? Table Sugar C12H22O11

Element, Compound, or Mixture? Diamond

Element, Compound, or Mixture? C Diamond

Element, Compound, or Mixture? Tea

Element, Compound, or Mixture? Salt

Element, Compound, or Mixture? NaCl Salt

Element, Compound, or Mixture? Neon Gas

Element, Compound, or Mixture? Ne Neon Gas

Element, Compound, or Mixture? Salad

Classifying Matter: Elements, Compounds, and Mixtures