1. Classification of Matter
Elements, Compounds, Mixtures

2. Physical and Chemical Changes
A NEW substance is formed.
These changes are irreversible or permanent.
The new substance formed will have different properties compared to its original elements. (E.g. different melting and different chemical reactions from the original substance.)

3. Physical and Chemical Changes
One can recognize a chemical change from 2 observations:
The new substance has a different appearance, such as different color or different physical state.
An example is the electrolysis of water.
Reason: Electrolysis of water produces two new substances, Hydrogen gas and oxygen gas. Hydrogen and oxygen are both gases but water is a liquid.
A lot of heat is given out in a chemical changes.
Chemical changes are called chemical reactions.

4. Venn Diagram Compounds Elements Made from 2 or more different element
Pure substance
Found on
Periodic Table
Made of atoms
Formed through
chemical reaction
Essential for life
92 found free
in the environment
Found in nature
Smallest part
is an molecule
Smallest part
is an atom

5. Compounds Elements Formed through chemical reaction Found on
Periodic Table
Pure substance
Made from 2 or
more different
element
92 found free
in the environment
Smallest part
is an atom
Smallest part
is an molecule

6. These are elements! H H He O Na O O Cu Atoms of same element
Molecules of same element H H Cu He
Hydrogen gas element
copper element
helium element O
ozone Na O O
sodium element

7. Molecules
For example, hydrogen is H2.
Very few elements exists as atoms besides elements such as helium and neon.
Most elements exist as molecules.
Ozone is O3.

8. Introducing Little Miss “Compounds”
Harlow! Hehee!!!
*giggles*
I am also a PURE SUBSTANCE
I am made up of a fixed number of two or more elements chemically combined.

9. Compounds Note that a compound:
can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means),
has properties that are different from its component elements, and
always contains the same ratio of its component atoms.

10. What is a compound?
A compound is a substance which is made up of two or more elements chemically combined together.
Chemical reactions taking place.
Qn: Is this a compound?
Qn: Is this a compound?
Qn: Is this a compound? H H O Cu
It only contains one type of element.
It only contains one type of element. O
It is not chemically combined. H H O

11. So, what is a compound then?
Water
Ammonia gas
Consists of two or more elements
And
They are chemically combined together!

12. Fixed Composition of Compounds
A compound is made up of different elements chemically combined in a fixed ratio.
For example, water (H2O) is a compound made only by joining together two atoms of hydrogen to one atom of oxygen. That is, the ratio of hydrogen atoms to oxygen atoms in water is always 2 : 1.

13. Chemical Formula of a Compound
A compound can be represented by a chemical formula.
The chemical formula states • the types of atoms (i.e. elements) in the compound, • the ratio of the different atoms in the compound.
Types of atoms: hydrogen, oxygen
Ratio of H to O = 2:1
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14. How do we write chemical formula? Rule 2
The number of atoms is written as a subscript, to the right of the atom’s symbol.
• water: (H2O, not H2O or 2HO)
• magnesium carbonate: MgCO3, not MgC3O)

15. How do we write chemical formula? Rule 3
It is not necessary to write the subscript ‘1’.
• water (H2O, not H2O1) • calcium oxide (CaO, not Ca1O1)

16. How do we calculate the number of atoms in a formula?
Number of Hydrogen (H) atoms = 12
Number of Carbon (C) atoms = 6
C6H12O6
Number of oxygen (O) atoms = 6

17. Summarizing
A compound is made up of two or more elements chemically joined together
A compound has a fixed composition
Every compound has a unique chemical formula
A compound has a completely different properties from its elements
A chemical reaction is needed to separate the elements in the compound

18. Molecules- Elements or compounds?
A molecule consists of two or more atoms of the same element, or different elements, that are chemically bound together.
It can be a molecule of an element
E.g. N2, O2, S8
It can be molecule of a compound.
H2O, CO2, NH3 N O S O H C N

19. Conclusion
An element is a pure substance which cannot be split up into two or more simpler substances by chemical means.
A compound consist of a fixed number of different kinds of atoms chemically combined together.
A mixture is not a pure substance as it contains a mixture of atoms of molecules which are not chemically combined together.

20. Challenge Time
Element, Compound or Mixture?

21. Challenge Time
Element, Compound or Mixture?

22. Common Household items
Common Name
Formula
Dry Ice
CO2
Rock Salt
NaCl
Epsom Salt
Ammonia
NH3
Bleach
NaClO
Chalk
CaCO3
Vinegar
CH2COOH
Hydrogen Peroxide
H2O2
Alcohol
C3H3O
Baking Soda
NaHCO3

23. EXTRA! Human body is made up of 28 elements?
About 99% our mass is made up of the 6 main elements
Oxygen (65%)
Carbon (18%)
Hydrogen (10%)
Nitrogen (3%)
Calcium (1.5%)
Phosphorus (1.5%)