Transcript Chemistry a material science!

Chemistry is a material
science!
Define Chemistry
Definition
Chemistry is the study of
matter: its composition, the
changes matter undergoes,
and the energy associated
with these changes.
Matter Defined
Matter is anything that has
mass and takes up space, or
has volume.
Density: a spin-off
This fundamental definition of
matter leads to a common
property of matter, namely,
density. Density is equal to
the mass divided by the
volume.
Composition
The “makeup” of matter is its
composition. This answers the
question what kind of atoms
and molecules are present in
this matter.
Substances
Matter composed of only one
kind of particle such as an
atom or molecule is a pure
substance or simply a
substance.
Substances are made of only
one kind of element or
compound.
Physical Properties
Substances have physical
properties such as melting and
boiling temperature, solubility
and density.
Physical properties can be
observed without changing the
composition of matter. For
example, copper wire can
conduct electricity and remain
copper.
Chemical properties deals with
how a substance will react
with another substance.
Neon gas is non reactive with
all substances. Sodium metal
is highly reactive and must
kept under oil to prevent
reaction with air or water.
The chemical property of a
substance is basically its
reactivity.
Physical properties that are
the same regardless of the
sample size are called
intensive properties.
Intensive properties such as
density and melting
temperature can be used to
identify the substance.
Extensive properties such as
mass or volume will vary with
the sample size.
Elements are composed of the
same type of atom (same
element e.g. Ne) or molecules
of the same type of atom
(element e.g. N2).
Compounds are composed of
atoms of different elements in
definite ratios. Carbon dioxide
is CO2 and carbon monoxide
is CO.
Mixtures are a combination of
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An element with element or
Element with a compound or
Compound with other compounds
Mixtures are a combination of
substances with variable mass
ratios.
Changes in matter can be
classified as a physical
change, a chemical change
or a nuclear change.
Substances undergoing a
physical change may have an
alternate state of matter or
change in shape, but never
change in composition of the
substance itself.
When H2O(l) as a liquid
freezes it is H2O(s) as a solid,
but there is no change is the
fixed ratio of H:O in H2O.
Thereby there is not change in
the composition.
Chemical changes are called
chemical reactions and are
more difficult to reverse than
physical changes.
In a chemical reaction new
substances (called products)
are formed with a new and
different set of physical and
chemical properties.
For example, when H2 and O2
react to form H2O. The H2O
that extinguishes flames was
produced from O2 that supports
combustion and H2 that is
highly flammable
Likewise the freezing and
boiling temperature of both H2
and O2 is much lower than the
corresponding freezing and
boiling temperature of H2O.
A nuclear change releases the
most of energy of all the
changes. In nuclear reactions
atoms of one element are
often changed into atoms of
different element.
Energy associated with changes.
Type of change in
matter
Change in Energy
Physical Change
H2O(s) H2O(l)
Chemical Change
334 joules needed
endothermic
285.8 kJ
exothermic
1.7 x 109 kJ
exothermic
2H2(g) +O2(g)  2H2O(l)
Nuclear Fusion
3H + 2H4He + 1n