Chemistry is the study of
matter
Learning objectives
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Describe the three states of matter
Distinguish among the three states based on given
properties
Describe features of pure substance, mixture, element and
compound
Distinguish among pure substances, mixtures, elements
and compounds
Describe essential meaning of physical and chemical when
applied to properties and changes in chemistry
Identify whether change is physical or chemical based on
observations
The Nature of Matter
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All matter is made of something, even if it
looks like nothing.
 We make classifications according to its
properties, both chemical and physical
Three States of Matter
Solid: strong interactions
•Fixed shape
•Not compressible
•Rigid
•Dense
Liquid: medium interactions
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Liquid
Not rigid
Assumes shape of
container
Not compressible
Dense
Gas: no interactions
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Not rigid
 Completely fills
container
 Compressible
 Low density
All matter is either pure or impure
Matter
Pure
Impure
(>1 pure substance)
•Pure matter cannot be separated by physical means
•Impure matter can be separated by physical means
•Another word for impure matter is mixture – a
solution is a common example of a mixture
What are physical means?
Any process that doesn’t change
composition
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Filtration and centrifuge
(liquids and solids)
Crystallization (solutions)
Distillation (solutions of
liquids)
Magnetism (magnetic
from non-magnetic)
Chromatography (gases
and liquids)
Mixtures are either homogeneous
or heterogeneous
Matter
Pure
Homogeneous
(uniform even on molecular scale)
Impure
Heterogeneous
(non-uniform)
Pure materials are also divided
Matter
Pure
Element
(not divisible by chemical means
Impure
Compound
(divisible by chemical means)
Compounds are not mixtures
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Compounds have specific compositions
(ratio of elements always the same - NaCl)
 Mixtures have variable composition
 Compounds have properties different from
those of elements
 Mixtures have similar properties to those of
constituents
Sodium chloride is made from
sodium and chlorine
•ELEMENTS:
•Sodium: metal,
very reactive
•Chlorine: gas,
very reactive,
highly toxic
•COMPOUND
•Sodium chloride:
salt, unreactive,
harmless
Chemical and Physical
Properties
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Physical properties: things that we can measure
about a substance without changing its
composition (always the same for a pure substance)
o
o
o
o
o
o
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Melting point
Boiling point
Density
Electrical conductivity
Thermal conductivity
Colour
Chemical properties: how substances behave in
chemical reactions (always involves change in composition)
Chemical and Physical Change
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Physical change: changes where ultimately
no change in the chemical composition
occurs – easily reversible
o Change of state (melting, boiling etc.)
o Dissolving
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Chemical change: a change where a
chemical reaction occurs
Decide for yourself:
Chemical or physical?
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Grape juice turns to wine
 Wood burns to ashes
 Water boils
 Leaves turn yellow in Fall
 Rock is crushed to powder
 Salt dissolves in water