MATTER
AND
CHANGE
Chemistry:
The study of matter and
the changes it
undergoes.
Matter
Anything that has mass
and takes up space
Alchemical view of matter
Matter
• Atoms are the building blocks of matter
Matter
“Space-filling” models of molecules
Matter
Oxygen
Hydrogen
Each element is made of the same kind of atom
Each element is made of the same kind of atom with
unique set of properties
Carbon
Uncut
diamond
Graphite
Uncut diamond
with impurities
STATES OF MATTER:
Solid, Liquid, Gas
(a) Particles in solid
(b) Particles in liquid
(c) Particles in gas
STATES OF MATTER
• SOLIDS
– Definite shape and
volume
– Particles of a solid
packed tightly together
– NOT easily
compressed
SOLIDS
STATES OF MATTER
• LIQUIDS
– Particles in close
contact but
arrangement is not
orderly or fixed
– Definite volume
– NOT easily
compressed
In a liquid
• molecules are in
constant motion
Liquid
• there are appreciable
intermolecular forces
• molecules are close
together
• Liquids are almost
incompressible
• Liquids do not fill the
container
H2O(l) Water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31
STATES OF MATTER
• GAS
– Particles NOT in close
contact and are
constantly moving
– No definite volume
Some Properties of Solids, Liquids, and Gases
Property
Solid
Liquid
Gas
Shape
Has definite shape
Takes the shape of
the container
Takes the shape
of its container
Volume
Has a definite volume
Has a definite volume Fills the volume of
the container
Arrangement of
Particles
Fixed, very close
Random, close
Random, far apart
Interactions between
particles
Very strong
Strong
Essentially none
How to describe matter…
• Extensive properties
– Depends on the
AMOUNT of matter in
a sample
• Mass
• Volume
• Intensive properties
– Depends on the TYPE
of matter in a sample
• Color
• Temperature
• Density
SUBSTANCE
• Matter that has a uniform and definite
composition
• Every sample of a given substance has
identical intensive properties because
every sample has the same composition
• Elements CANNOT be broken down into
simpler components
• Compounds CAN be broken down into
elements
Examples of pure substances
GOLD
ALUMINUM
Compounds
• Made of two or more different kinds of elements
chemically combined in a fixed proportion.
– for example:
• Common table salt is a one to one combination of sodium
atoms (Na) and chlorine atoms (Cl) = NaCl
What do we mean by
“chemically combined”?
• Elements in compounds are joined by
chemical bonds.
– Examples of chemical bonds:
• Ionic bond (electrostatic attraction that binds
oppositely charged ions)
– Usually composed of metal and nonmetal atoms
• Covalent bond (bond that forms by the sharing of
electrons between atoms)
– Usually composed of carbon atoms bonded to elements
such as hydrogen, oxygen, nitrogen and sulfur
Properties of Compounds
• Compounds can be broken down into
simpler substances by chemical means
but elements cannot.
• Compounds and the elements from which
they are formed have different properties
Examples of Compounds
• Sugar (sucrose)
– Composed of carbon, hydrogen and oxygen
• Sugar a sweet-tasting white solid but carbon is a
black, tasteless solid; Hydrogen and oxygen are
odorless gasses
Sugar
Carbon
+
Water
http://www.youtube.com/watch?v=A_jtOpAYG70
Sugar (sucrose)
Sugar (sucrose)
Properties of Matter
• Physical properties:
– Can be observed without changing a
substance into another substance
• Boiling point, density, mass, volume, magnetic
Properties of Matter
• Physical changes
– Changes in matter that do NOT change the
composition of a substance
• Changes of state (liquid to a gas), temperature
(melting point), volume, crush, grind
• Chemical changes
– Changes that result in a new substance
• Combustion, oxidation, decomposition
Mixtures
• Physical blend of two or more components
• Heterogeneous = composition is variable
throughout the sample
• Homogeneous = composition is uniform
throughout the sample
Classification of Matter