1. Classification of Matter
Elements, Compounds, Mixtures

2. Lesson Objective Physical and Chemical Changes. Elements Compounds
Mixtures

3. Physical and Chemical Changes
All reaction in Chemistry can be divided into two types of changes: Physical or Chemical.
Physical Change:
NO new substance is formed.
These changes are easily reversible or temporary.
An example is dissolving salt in water.
Other examples of physical change include: melting, boiling, mixing 2 solids or liquids.

4. 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.)

5. 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.

6. Illustration of chemical changes

7. An Overview

8. Elements, Compounds and Mixtures
“ single, attached, play play…”

9. Introducing Little Miss “Element”
Hi! I am Little Miss “Element”
I am PURE SUBSTANCE
I cannot be broken down into any simpler substance by means of a chemical reaction* or electricity**!
*Chemical process refers to chemical reaction or heat
**Electricity refers to electrolysis

10. Definition of an element:
Elements
Definition of an element:
An element is a pure substance which cannot be split up into two or more simpler substances by chemical means.
Sugar is not an element as it can be broken down into carbon and water.

11. Elements Note that an element: Consists of only one kind of atom,
Cannot be broken down into a simpler type of matter by either physical or chemical means
Can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).

12. Examples of elements Molecules Atoms
Elements are made up of tiny particles
Elements can be further classified into two groups:
Molecules
Atoms
Is made up of two or more
atoms that are chemically
bonded together
(note: these atoms are of the
SAME element!!)
Is the smallest particle
of an element and has
the same chemical properties
of the element
Hi, I am from the “Noble gas” family and I work alone
We same same!!

13. 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

14. Atoms An element is made of tiny particles called atoms.
The atoms of an element is different from that of another element.

15. Consists of only one kind of atom
Elements- Atoms
Consists of only one kind of atom
Microscopic view of the atoms of the element argon (gas phase).

16. What is an atom? Cl H Na Examples of models of atoms: Hydrogen atom
Sodium atom
Chlorine atom

17. 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

18. 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.

19. Molecules consisting of a few atoms are called polyatomic molecules.
Hydrogen (H2) is a diatomic molecule.
Molecules consisting of a few atoms are called polyatomic molecules.
Ozone (O3) is a triatomic molecule.

20. Consists of only one kind of atom
Elements-Molecules
Consists of only one kind of atom
Microscopic view of the molecules of the element nitrogen (gas phase).

21. Examples of molecules (elements)H S O S S S S S S N N S

22. Allotropes of Carbon molecule (element)
Carbon is an element but made up of a very large molecule (also known as MACROMOLECULE)
There are 3 types of carbon molecular structures
C60
Diamond
Graphite

23. Chemical Symbols of Elements
Chemists use symbols to represent elements. For example, O represents oxygen while Fe represents iron.
Element
Symbol
Calcium Ca
Mercury Hg
Carbon C
Neon Ne
Hydrogen H
Silicon Si
Iron Fe
Sodium Na

24. Classification of Elements – Metals and Non-metals
There are two major groups of elements – metals and non-metals.
Iron is a metal. Oxygen is a non-metal.
Metals and non-metals are grouped separately on the Periodic Table.
There are some elements called metalloids which behave like both metals and non-metals.

25. Non-metals (including hydrogen)
What is an element?
An element is a substance that cannot be broken down into two or more simpler substances by any chemical means.
- They are arranged in the Periodic Table, classified as metals and non-metals.
- They may consist of atoms of same element or molecules of the same element.
Non-metals (including hydrogen)
Metals (excluding hydrogen)

26. Physical Properties metals and non-metals
Shiny appearance
Dull appearance
Solids at r.t.p (except mercury)
Gases, liquids or solids at r.t.p (room temp & pressure)
Malleable, Ductile, Sonorous
Brittle if solid (general)
High melting and boiling points
Low melting and boiling points
Good conductors of heat
Poor conductors of heat
Good conductors of electricity
Poor conductors of electricity
(expect carbon and graphite)

27. Summarising
Elements
Metals
Non
Metals
Atoms
Atoms
Molecules

28. 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.

29. 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.

30. 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

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

32. Compounds
Microscopic view of the molecules of the compound water (gas phase). Oxygen atoms are red and hydrogen atoms are white.

33. Making compounds from their elements
Example: Making water (picture)
lighted splint
ELEMENTS
COMPOUND
hydrogen
(colourless gas)
oxygen
(colourless gas)
heat, light and explosion
water
(colourless liquid)
Example: Making water (models)
mixture of hydrogen and oxygen
water
heat, light and explosion
Water molecule
Hydrogen molecule
Oxygen molecule

34. Making compounds from their elements
Example: Making iron sulphide compound
compound
elements
heat
Iron sulphur  iron sulphide + 
heat
yellow
grey
black

35. Little Miss “Compound” Property #1
I can be represented as a “chemical formula”
The different elements present in a compound are combined in a fixed ratio
General Rules:
- Only write the name of the metallic element
first
- Write the number of atoms of any element
in the compound in subscript
(applies to only 2 or more atoms)
- “ide” will always be written at the
end of the non metal element
Special Rules:
Does not apply to organic compounds
(chapter 18 onwards)

36. Little Miss “Compound” Property #2
I am formed by atoms of different elements. However, I do not have the properties as them.
Examples
Na + Cl2  NaCl
(s) (g) (s)
H2 + O2  H2O
(g) (g) (l)

37. Little Miss “Compound” Property #3
Electrolysis
(breaking down of compound by electricity)
2MgCl(s)  Mg(s) +Cl2(g)
Thermal Decomposition
(breaking down of compound by heat)
HgO(s)  Hg(s) + O2(g)
Because of my chemical bonds, I cannot be broken down by physical means. I can only be broken down by chemical reaction or electricity.

38. How do we name compounds? Rule 1
A compound made up of two elements has a name that ends in -ide.
• Sodium chloride — made up of the elements sodium and chlorine • Zinc oxide — made up of the elements zinc and oxygen • Carbon dioxide — made up of the elements carbon and oxygen

39. How do we name compounds? Rule 2
A compound that contains hydroxide ions , OH– (a negatively charged ion made up of oxygen and hydrogen) is named a hydroxide.
• Potassium hydroxide — contains potassium ions and hydroxide ions

40. How do we name compounds? Rule 3
A compound that contains a negatively charged polyatomic ion containing oxygen usually has a name ending in –ate.
• Copper(II) sulphate — contains oxygen atoms in the sulphate ion • Sodium nitrate — contains oxygen atoms in the nitrate ion

41. 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.

42. 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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43. How do we write chemical formula? Rule 1
For many compounds that contain both metallic and non-metallic elements, the symbol of the metallic element is written first.
• calcium oxide (CaO) • sodium chloride (NaCl) • magnesium carbonate (MgCO3)

44. 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 MgCO3 or MgC3O)

45. 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)

46. How do we write chemical formula? Rule 4
The oxygen atom is usually written at the end of the formula.
• water (H2O, not OH2) • carbon dioxide (CO2, not O2C) • nitric acid (HNO3, not O3NH)

47. How do we calculate the number of atoms in a formula?
Number of nitrogen (N) atoms = 1 x 2 = 2
Number of lead (Pb) atoms = 1
Pb(NO3)2
Number of oxygen (O) atoms = 3 x 2 = 6

48. Compounds can be Decomposed
Heat can be used to break down compounds into elements or simpler compounds. Such a chemical reaction is called thermal decomposition.
Oxygen
Mercury(II) oxide

49. 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 (decomposition or electrolysis) is needed to separate the elements in the compound

50. Introducing Little Mr. “Mixture”
Burp!!!! I am messy!
I am formed when two or more substances joined together physically (without chemical bonds)
I have the same properties as all the substances
I am his best friend!
AIR

51. Think about this…
ROJAK!!

52. Definition of a mixture:
Mixtures
Definition of a mixture:
A mixture is not a pure substance as it contains a mixture of atoms of molecules which are not chemically combined together.

53. Mixtures Note that a mixture:
consists of two or more different elements and/or compounds NOT chemically combined.
Can be homogeneous or non-homogeneous
can be separated into its components by physical means, and
often retains many of the properties of its components.

54. Mixtures
Microscopic view of a gaseous mixture containing two elements (argon and nitrogen) and a compound (water).

55. Mixtures
Examples of mixtures include muddy water and air. Air is made up of gases such as nitrogen and oxygen mixed together.

56. He can be separated to its substances by physical methods
Little Mr “Mixture”
I do not have a fixed composition of the substances.
A Mixture can be:
element + element
element + compound
compound + compound
(Refer to page 59, Fig 4.7)
He is a “boo-boo!”
He can be separated to its substances by physical methods

57. A mixture of 2 elements
A mixture of two elements, e.g. neon (Ne) and hydrogen (H2)

58. A mixture of 1 element and 1 compound
A mixture of one element and one compound, e.g. hydrogen (H2) and ammonia (NH3)

59. A mixture of 2 compounds
A mixture of two compounds, e.g. water vapour (H2O) and carbon dioxide (CO2)

60. Alloy: What is it?? It is a mixture of metals with other elements
Alloy metals are generally stronger and better in physical properties
Examples
Steel (Iron + Carbon)
Stainless Steel (Nickel + Iron + Chromium + carbon)
Brass (Copper + Zinc)
Mr Alloy
Yup!
That’s
ME!

61. Mixture of 2 elements-Alloy
Can you differentiate?
Mixture of 2 elements-Alloy
Molecules of an element
Compound
Mixture of element & compound
Mixture of 2 elements

62. 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.

63. Difference between mixtures and compounds.
E.g.
Water H2O
Mixtures
Salt solution
Separation
Cannot be separated into its constituents by physical methods. Separation can only be done by chemical methods or by electricity.
e.g. Water can only be separated into Hydrogen and Oxygen by Electrolysis.
Can be easily separated into its constituents by physical methods.
e.g. Salt can be obtained from its solution by evaporation. Water can be obtained by simple distillation.

64. Difference between mixtures and compounds.
E.g.
Water H2O
Mixtures
Salt solution
Composition
The composition is fixed. The constituents (elements) in the compound are combined in definite amount.
e.g. To form one molecule of water, two atoms of Hydrogen and one atom of Oxygen is needed.
Has no fixed composition. The amount of constituents in a mixture can vary.
e.g. The amount of salt added into the water to make salt solution can vary and vice versa.

65. Difference between mixtures and compounds.
E.g.
Water H2O
Mixtures
Salt solution
Properties
The physical and chemical properties of the compound is different from the properties of its constituents.
e.g. Hydrogen and Oxygen are gases while water is a liquid at room temperature and pressure.
e.g. Water has a fixed melting and boiling point.
The mixture does not have its own properties. It has the average physical and chemical properties of the constituents that made it up. (Each constituents still retain its own properties)
e.g. The salt solution still retains its salt taste.
e.g. Salt solution does not have a fixed melting or boiling point, but rather over a range of temperature.

66. Difference between mixtures and compounds.
E.g.
Water H2O
Mixtures
Salt solution
Energy Change
Energy is usually given out or occasionally taken in when a compound is formed.
Normally little or no energy is given out or taken in when a mixture is formed.

67. Differences between mixtures and compounds
Laugh what? I know I am a little “bushy and hairy” than you…
*giggles*
HeE stupid… VS
Mr Messy
Little Miss Compound

68. Comparison between mixtures and compounds
Separation
/breakdown
Components can be separated by physical methods
Elements in a compound Cannot be separated by physical methods
Properties
(chemical / physical)
Same properties as its components
Properties are unique and different from its elements
Energy Change
No chemical change takes place when a mixture in formed
A chemical reaction takes place when a compound is formed
Mp / Bp
Variable
Fixed
Composition
Does not have a fixed composition
Has a fixed composition

69. Challenge Time
Is mineral water an element, mixture or compound?

70. Challenge Time
Are YOU an element, mixture or compound?

71. 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%)

72. The End……