1. In This Section We Will Be Studying The Following Topics:
ATOMS AND ELEMENTS
In This Section We Will Be Studying The Following Topics:
Different materials.
Elements & atoms.
How elements differ.
How are non-elements formed?
Chemical reactions.
Predicting chemical reactions.

2. I don’t know Professor. They seem different to me.
DIFFERENT MATERIALS
Plastic bin.
Nails in a tin.
Ayers rock.
Charcoal.
Wood.
Water.
Volcanic gases.
Moley, what do these objects have in common?
I don’t know Professor. They seem different to me.
They are different types of materials. When scientists talk of a material they do not just mean cloth but anything that can be touched, including gases.

3. Are these items natural or man-made?
DIFFERENT MATERIALS
In prehistoric times there were only natural materials e.g. wood, stone, bones, water etc. As men grew in knowledge and skills they started to make materials like pottery, bronze, glass.
Nowadays there are millions of manmade materials.
In fact most everyday objects do not contain any natural materials.
Are these items natural or man-made?

4. DIFFERENT MATERIALS
All the millions of different materials, natural and man-made, are themselves made from a set of very basic materials that are called elements. Over 100 of these elements have been discovered and they combine in different ways to make the other materials.
Let us have a look at how millions of different materials can be made from about 100 elements.
We will take a simple example using 4 colours yellow, green, blue & purple.
With two colours we can have:
1 combination
With three colours we can have:
4 combinations
With four colours we can have:
11 combinations
So from 4 colours we have 11 combinations.
If we had 20 colours we would have about one million combinations.

5. Can you find the letter codes for the other elements listed above?
DIFFERENT MATERIALS
Scientists have created a table that shows all the elements. They have put them in order according to their chemical properties. The table is called the Periodic Table of elements. Ac Ra Fr Rn At Po Bi Pb Tl Hg Au Pt Ir Os Re W Ta Hf La Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr B Se As Ge Ga Zn Cu Ni Co Fe Mn Cr V Ti Sc Ca K Ar Cl S P Si Al Mg Na Ne F O N C Be Li He H
From your previous science lessons you will have come across the names of some elements.
For example: iron, copper, aluminium, hydrogen, oxygen, carbon, sodium, calcium.
Scientists use a letter code (called a symbol) for the elements, for example copper = Cu
Can you find the letter codes for the other elements listed above?

6. This is not an element. It has more than one type of atom.
DIFFERENT MATERIALS
We have said that materials are made up of elements, but what are elements made from?
Scientists have discovered that the smallest piece of any material is an Atom. Atoms are so small that they can only be seen through special high powered microscopes.
Materials are made up from several different types of atoms. The types of atoms depend on the elements used to make the material.
Elements are special because they only contain one type of atom.
This is an element.
This is not an element. It has more than one type of atom.

7. DIFFERENT MATERIALS
We usually represent atoms as circles. We know which element the circle represents by the letter (called the symbol for the element) in the circle. O C Al H Cu
Oxygen
Carbon
Aluminium
Hydrogen
Copper
To help even further, some of the more common elements will have their circles coloured. Be careful, the colours used are not always the colour of the element. O C Cl H S
Carbon dioxide is a non-element and we can show it like this:
Element.
Are these elements or non-elements?
Non-element, 3.
Non-element, 2.
If they are non-elements how many elements do they have?
Non-element, 5.
Element.

8. How an element looks and behaves are called its properties.
HOW ELEMENTS DIFFER
As more and more elements were discovered, scientists started to realise that while many behaved differently, some behaved in similar ways.
How an element looks and behaves are called its properties.
The way an element or non-element looks (colour, shiny etc), feels (rough, smooth etc) and whether it is a liquid, solid or gas are called its physical properties.
Can you use the list of physical properties above to describe these materials?
Copper.
Soap.
Diamond.
Oil.
How a material behaves chemically with other materials is called its chemical properties.

9. There are two examples of colour coding on the next slide.
HOW ELEMENTS DIFFER
Scientists classify elements according to their properties.
Usually, the first properties that scientists look at when classifying an element are:
Is it a solid, liquid or gas at room temperature (20oC)?
Is it a metal or non-metal?
Is it magnetic or non-magnetic?
At what temperatures does it melt and boil?
We can use the Periodic Table to help us look at elements with similar properties by using colour codes. For instance, we can colour all metals one colour and non-metals another colour.
There are two examples of colour coding on the next slide.

10. HOW ELEMENTS DIFFER Metals & non-metals Solids, liquids & gasesAc Ra Fr Rn At Po Bi Pb Tl Hg Au Pt Ir Os Re W Ta Hf La Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe Mn Cr V Ti Sc Ca K Ar Cl S P Si Al Mg Na Ne F O N C B Be Li He H
Metals
Metals & non-metals He Ac Ra Fr Rn At Po Bi Pb Tl Hg Au Pt Ir Os Re W Ta Hf La Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe Mn Cr V Ti Sc Ca K Ar Cl S P Si Al Mg Na Ne F O N C B Be Li H
Liquids
Gases
Solids
Solids, liquids & gases

11. HOW ARE NON-ELEMENTS FORMED?
When different atoms join together, the material they make is never an element. The properties of the new material are often different to the properties of the elements that join.
1 Atom O H
Colourless Gas
2 Atoms
Joins
1 molecule
Liquid Water
To make S
2 Atoms O
Colourless Gas
1 Atom
1 molecule
Yellow Solid
Joins
To make
Fill in the question marks: C
? Atoms O
Colourless Gas
? Atom
1 molecule
Black ?
Colourless ?
Joins
To make 2 1
Solid
Gas

12. HOW ARE NON ELEMENTS FORMED?
When two or more different atoms join together, the new material formed is called a compound. C H O H H
Hydrogen is not a compound.
Liquid water is a compound.
Methane is a compound.
When two or more atoms, the same or different kinds, join together they make a molecule. O H C H H
What is water?
Hydrogen is a molecule of an element.
Methane is a molecule of a compound.
A molecule of a compound.

13. CHEMICAL REACTIONS
Chemical reaction or chemical change are the words used to describe what happens when atoms join to make molecules of a compound. The chemical atoms are said to react together.
So what the reactants produce when they react, are the Products.
We call the chemicals that join together the Reactants.
1 Atom O H
Reactant.
2 Atoms
1 Molecule
Product.
Joins
To make
Coal burns in oxygen to make carbon dioxide and water.
Which are the reactants and which are the products in the above chemical reaction?
Coal & oxygen are the reactants.
Carbon dioxide and water are the products.

14. Coal burns in oxygen to make carbon dioxide and water.
CHEMICAL REACTIONS
Coal burns in oxygen to make carbon dioxide and water.
A more scientific way of writing the above sentence would be:
‘Coal reacts with oxygen to produce carbon dioxide and water.’
Scientists have shortened this sentence more by using ‘+’ and ‘→’ instead of ‘reacts with’ and ‘produces’. This gives a Word Equation as follows:
coal + oxygen→ carbon dioxide + water
+ is used if there is more than one product.
Finally, a model for the reaction can be drawn similar to those which we have seen already. O C O H
Coal O + +

15. PREDICTING CHEMICAL REACTIONS
Some elements have similar chemical properties. So if we know how one element behaves we can make a good guess (predict) how similar elements will behave.
Many metal elements have similar chemical properties. If we know that copper reacts with oxygen to produce copper oxide, we can predict that:
copper + oxygen → copper oxide or magnesium + oxygen → magnesium oxide
You can see that the name of the products usually contains the names of the reactants.
copper + sulphur → copper sulphide and lead + sulphur → lead _________
sulphide
The opposite is also true. If we know the name of the product we can have a good idea of the reactants. Lead chloride probably has the reactants lead and chlorine.
What are the likely reactants for the following products?
carbon monoxide
sodium chloride
sodium and chlorine
carbon and oxygen

16. PREDICTING CHEMICAL REACTIONS
In everyday life we do not use chemical names. For instance, hydrogen oxide is water, sodium hypochlorite is bleach and we do not ask someone to pass the sodium chloride but to pass the salt.
Scientists need to be more certain of what they mean when talking to each other, so they have come up with some naming rules, one of which is:
Chemical Name
Contains Elements
Chloride
Oxide
Sulphide
Sulphate
Fluoride
Bromide
Carbonate
Chlorine
Oxygen
Sulphur
Sulphur & oxygen
Fluorine
Bromine
Carbon & oxygen

17. WHAT WE HAVE LEARNED?
When scientists talk about materials they mean any solid, liquid or gas.
Materials have Chemical & Physical properties.
Materials are usually made up of combinations of elements.
There are over 100 elements.
Elements have only one type of atom.
Compounds are made up of a number of different atoms.
Chemicals react together to make new chemicals.
They are called the Reactants and the Products.
The products can be ‘guessed’ from the reactants and often the reactants can be ‘guessed’ from the products.