1. Chemical Formula
D. Crowley, 2007

2. Chemical Formula
To understand chemical formula

3. Definitions Define an element, compound and mixture
An element is made up of just one type of atom
A compound is two or more elements, chemically bound
A mixture is made of different substances, not chemically bound

4. Elements & Compounds
Look at the rocket - it uses liquid hydrogen as a fuel
The engine mixes this hydrogen with oxygen, adds a spark and the reaction takes place
The elements are
They react together, forming a compound called

5. Elements & Compounds
Look at the rocket - it uses liquid hydrogen as a fuel
The engine mixes this hydrogen with oxygen, adds a spark and the reaction takes place
The elements are hydrogen and oxygen
They react together, forming a compound called
hydrogen oxide (water)!

6. Carbon + oxygen  carbon monoxide
Chemical Equations
Chemical equations show us our reactants and products
reactants  products
They can be word or symbol equations, e.g.
Carbon + oxygen  carbon monoxide
C + O  CO

7. Formula
Elements and compounds can be represented using chemical formula
We use numbers in the formula, which represents the number of atoms present (as a ratio)
C = 1 atom of carbon (C)
O2 = 2 atoms of oxygen (O)
CO2 = 1 atom of carbon (C); 2 atoms of oxygen (O)
NaCl = 1 atom of sodium (Na); 1 atom of chlorine (Cl)
H2SO4 = 2 atoms of hydrogen (H); 1 atom of sulphur (S); 4 atoms of oxygen (O)

8. Graphical Can you draw the following substances
The formula should help you graphically represent them…
Oxygen O2
Carbon dioxide
CO2
Sodium chloride
NaCl
Sulphuric acid
H2SO4
Carbon C
Nitric acid
HNO3

9. Graphical Can you draw the following substances
The formula should help you graphically represent them…
Oxygen O2
Carbon dioxide
CO2
Sodium chloride
NaCl
Sulphuric acid
H2SO4
Carbon C
Nitric acid
HNO3

10. Graphical Can you draw the following substances
The formula should help you graphically represent them…
Oxygen O2
Carbon dioxide
CO2
Sodium chloride
NaCl
Sulphuric acid
H2SO4
Carbon C
Nitric acid
HNO3

11. Graphical Can you draw the following substances
The formula should help you graphically represent them…
Oxygen O2
Carbon dioxide
CO2
Sodium chloride
NaCl
Sulphuric acid
H2SO4
Carbon C
Nitric acid
HNO3

12. Graphical Can you draw the following substances
The formula should help you graphically represent them…
Oxygen O2
Carbon dioxide
CO2
Sodium chloride
NaCl
Sulphuric acid
H2SO4
Carbon C
Nitric acid
HNO3

13. Graphical Can you draw the following substances
The formula should help you graphically represent them…
Oxygen O2
Carbon dioxide
CO2
Sodium chloride
NaCl
Sulphuric acid
H2SO4
Carbon C
Nitric acid
HNO3

14. Questions
Write down how many atoms there are (and of what element) for the following: -
C - e.g. 1 x carbon (C)
CO2
H2O
CaCO3
H2SO4
NaCl
HNO3
CuCO3
MgCl2
Carbon monoxide
Hydrogen oxide

15. Presentation
If there is time left, produce a poster in your book which explains formula (as a revision guide)
You may wish to add examples, and ways to work out the ratio of atoms…