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How do we get all other materials?
• Aims:
– To be able to classify materials as elements and non-elements
– To be able to describe simple compounds and molecules
Elements
• Elements are the simplest chemicals. They make up all other chemicals.
• Oxygen (O2) is an element:
• Elements have only one type of atom in their molecules
O O
Combining elementsHow is possible to have so many different materials from a limited number of elements?
Combining elements
How do you get so many different cheeses?
What is the key ingredient in all cheeses?
Milk is combined with a small number of ingredients under different conditions to make a huge number of different cheeses.
In a similar way, a small number of elements can be combined in many different ways to
make a huge number of different compounds.
Compounds
• Compounds are chemicals made when elements join together chemically.
• Water is a compound.
• Compounds have more than one type of atom in their molecules
H O H
Making a compound – carbon dioxide
A compound has very different properties to the elements from which it is made.
carbon dioxide
A colourless gas which is used
to put out fires.
to make
carbon
A black solid which can be
used as a fuel.
combines with
compound
elementsoxygen
A colourless gas which is essential
for life.
Making a compound – water What are the elements which make up water? In what ways are the elements different to their compound?
to makecombines with
compound
elementswater
A liquid which is essential to our lives and has
many different uses.
hydrogen
A colourless gas which is
used in hot air balloons.
A colourless gas which is essential
for life.
oxygen
More than one type of atom
• Elements join together to form compounds
• Water is a compound made from 2 elements– Hydrogen– Oxygen
• The smallest particle of water contains two atoms of hydrogen and one of oxygen– This is a molecule of water
Definitions
• Molecule– Two or more atoms joined together
• Compound– Chemicals made when two or more
elements join together chemically.