This document defines key chemistry concepts and differentiates between them. It explains that elements are substances that cannot be broken down further, and atoms are the smallest particles of elements. Compounds are formed by chemical combination of two or more elements. Mixtures contain two or more substances that are not chemically combined. The document outlines the differences between compounds and mixtures, noting that mixtures can be separated physically while compounds require chemical means to separate constituent elements. It also differentiates between pure substances and mixtures based on their composition and properties.

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