www.knowledgescroll.com After Viewing This Presentation You Should Be Able to: Distinguish between pure substances, mixtures and compounds. Show examples common mixtures. Discuss the various separation techniques of mixtures based on the different properties of the components.

1. CSEC CHEMISTRY REVIEW
2 - Separation of Mixtures and Compounds

2. OBJECTIVES
• Distinguish between pure
substances, mixtures and
compounds.
• Show examples common
mixtures.
• Discuss the various separation
techniques of mixtures based on
the different properties of the
components.
• Answer CSEC Chemistry
Questions.

3. • A pure substance is defined as any substance that is made
up of only one type of atom or molecule.
• When talking about pure substances consisting of single
atoms, we often refer to the word “Element”.
• Any matter which cannot be split into a simpler form by a
chemical process is known as an element.
• A list [118] of known and predicted elements can be found
in the Periodic Table of Elements.
WHAT IS A PURE SUBSTANCE ?

6. TABLE SHOWINGTHE NAMES OF ELEMENTS

7. Common Elements in the Earth’s Crust Common Elements Found in Organisms Common Elements Found in the Universe
oxygen (O) carbon (C) hydrogen (H)
silicon (Si) hydrogen (H) helium (He)
aluminium (Al) oxygen (O) oxygen (O)
iron (Fe) nitrogen (N) carbon (C)
calcium (Ca) phosphorus (P)
sodium (Na) sulfur (S)
potassium (K)
magnesium (Mg)
hydrogen (H)
TABLE SHOWING A LIST OF COMMON ELEMENTS IN NATURE

8. • There are very few, pure elements, that exist naturally
in our every day lives, what we usually interact with
are compounds.
• A compound is formed when two or more elements
are combined together chemically.
• For Example:
• Compounds can also be considered as pure
substances, when they are made up of just one kind
of molecule.

11. NB. Pure substances can be identified based on their well defined melting and
boiling points. Impure substances that may be contaminated, typically have lower
M.p. and B.p. than their pure equivalent.
TABLE SHOWING A LIST OF COMMON COMPOUNDS

12. WHAT IS A MIXTURE ?
• A mixture is a physical blend of two or more
substances (elements or compounds) in the same
space.
• There is no chemical interactions taking place in a
mixture and therefore the components of a
mixture may retain their original properties.
• In a mixture only physical properties like: colour,
size, density and state may be changed.

13. A mixture can be a combination of substances in
any two phases of matter. What do I mean?
Mixture Example Made Of Image
Solid in Solid Brass
Zinc + Copper
(Metal Alloy)
liquid in Liquid Rum Ethanol in Water
Gas in Liquid
Carbonated
Beverages (Coke)
Carbon dioxide in
Water
Gas is Gas Air
Nitrogen (78%)
and Oxygen (20%)

14. SUMMARY MIXTURESVS COMPOUNDS
No. Mixture Compound
1
The composition (mass) can
vary. It contains two or more
substances.
The composition (mass) is
always the same.A single
substance is formed.
2
Retains the properties of the
individual components.
The properties are very
different from the original
components.
3
No chemical change occurs.
Only physical changes.
A new substance is formed
through a chemical change.
4
Mixtures can be separated
quite easily by physical means.
Compounds are very hard
to separate and this can only
be done by chemical means.

15. • Mixtures can be separated in a number of ways and it is important
to know the various separation techniques.
• You may be asked to identify industrial scale separations of mixtures.
Like:
1. Separating the components of crude oil.
2. Separation of pure water from that stored in reservoirs or rain
water collectors.
3. Separation of useful gases such as oxygen (O2) and Nitrogen (N2)
from the atmosphere.
SEPARATION OF MIXTURES

16. Decantation is one process used for separating a liquid from an insoluble solid.
It is simple the pouring off of a liquid from a solid that has settled at the bottom of
the container (Precipitate).
We use this method quite other in cooking. Lets say you are washing vegetables or
rice in a bowl of water, when your finished you simple pour off the water.
1. DECANTATION

17. Filtration is used to separate a liquid from a suspended or settled
solid e.g. soil or chalk from water.
2. FILTRATION

18. Used for obtaining a solid from a mixture of a solid dissolved in a liquid, e.g. the sodium
chloride (salt) from its solution in sea water can be recovered by exporting all of the water
from the solution leaving the less volatile sodium chloride behind.This process is limited to
substances that do not decompose on heating, and those that do not retain water.
3. EVAPORATION

19. Crystallisation is used to separate and retain the solid solute from a solution
especially if the solid contains water of crystallisation, e.g. copper sulphate from
copper sulphate solution.
4. CRYSTALLISATION

20. To separate a pair of immiscible liquids (liquids that do not dissolve in each other), a
separating funnel can be used.This is a funnel with a stop-cork at the end. E.g.An oil
and water mixture,These two liquids occupy separate layers with the lighter oil on top.
The water is allowed to run out completely and then the oil can then be removed.
5. SEPARATING FUNNEL

21. This is a widely used method of separation and it is used to separate several solutes
present in a solution. E.g. dyes, inks, amino acids, sugars and pigments in chlorophyll
There are a few different forms of chromatography but the one that we will focus on
is paper chromatography.
6. CHROMATOGRAPHY

22. This is a process used to separate and retain a pure solvent from a solution.The
solution is boil and the liquid with lower boiling point vaporises, and travels into the
condenser.The vapour then cools and condenses back into a liquid where it is
collected.
7. DISTILLATION

23. There are other separation techniques that have not been mentioned
that you will need to know about such as:
1. Fractional Distillation (Industrial)
2. Solvent Extraction (Industrial)
3. Centrifuge Separation (Biological & Medical)
OTHER SEPARATIONTECHNIQUES

24. REFERENCES
• (Building Blocks of the World) https://
www.open2study.com/courses/chemistry
• Introduction to Solutions, Solute, and Solvent https://
www.youtube.com/watch?v=SaNZAyqOeT0
• A Concise Revision Course For CXC - AnneTindale
• CXC Revision for Chemistry - Comptom Mahase