1. Made by: M. Fahd-Un-Nabi Khan
USMAN PUBLIC SCHOOL
XI-O

2. Elements
 An element is a substance which cannot be split into
two or more substances by chemical means
 The smallest possible particle of an Element that can
take part in a chemical change is called an ATOM.

3. Compounds containing 2 or more
 Compound is substance
elements chemically joined together.
 e.g. Magnesium is an element; oxygen is an
element – they can only be combusted to form
magnesium oxide (MgO) compound.
 Ions or molecules make up compounds
 Ions are atoms having electrical charge, e.g. NaCl
made up of 2 ions; positively charged Na, negatively
charged Cl.

4. Molecules
 Molecule is group of two or more atoms chemically
joined together, e.g. chlorine molecule has 2 chlorine
atoms.
 Molecules can be either ELEMENTS or
COMPOUNDS.
 E.g. MgO is a compound, but Cl2 is an element

5. Mixtures
 2 or more substances which are not chemically joined t
ogether e.g. Iron in Sulphur powder.
 Can consist of:
 Elements (Iron & Sulphur powder)
 Compounds (Salt in water - salt & water are both
compounds)
 Elements + Compounds (Air; N2, O2, H2O)

6. Difference between Compounds and Mixtures
MIXTURE COMPOUNDS
 Constituent substances can  Constituent substances can
be separated easily by be separated only by chemical
physical means means
 Its physical and chemical  Its physical and chemical
properties are an average of properties are individual and
substances in it not the result of its elements
 A mixture’s proportion can  A compound’s proportion
vary cannot vary
 Little or no energy is involved  Energy is usually involved
when Mixture is formed when a Compound is formed

7. Diffrentiation between Pure and
Mixtures
 Pure Substances (elements, compounds)
1) Fixed composition
2) Fixed Mp/Bp
3) Produces only 1 spot on chromatogram
4) All molecules same (equal)
 Mixture
1) Variable Composition
2) Variable Bp/Mp
3) 2 or more spots on Chromatogram
4) 2 or more different molecules