ANYTHING WITH MASS AND VOLUME
Elements
Pure
Substances
Compounds
Matter
Homogeneous
Mixtures
Heterogeneous
Mixtures and Pure
Substances
• Matter that consists of two or more
substances mixed together but not
chemically combined is called a mixture.
• A pure substance is made of only one
kind of material and has definite
properties.
Elements
• Elements are the simplest pure
substance.
– Examples: hydrogen, carbon, and
oxygen.
• The smallest particle of an element
that has the properties of that
element is called an atom.
Compounds
• A molecule is formed when two or more
atoms combine.
• Compounds are pure substances that are
made of more than one element bound
together.
– Examples: water, table salt, and carbon
dioxide.
MIXTURES
Heterogeneous vs. Homogeneous
• Homogeneous matter: matter that has
identical properties throughout.
– Examples: Sugar, salt, water, and whipped
cream
• Heterogeneous matter: matter that has
parts with different properties.
– Examples: granite, soil, potpourri
Conservation
• Law of Conservation of Matter
(Mass): matter cannot be created or
destroyed.
• Law of Conservation of Energy:
Energy cannot be created or
destroyed; it may only change from
one form to another.
Matter and energy MUST be
conserved; it’s the LAW!
Virtually everything that is, is made up of
atoms.
From the very large...
To the very small...
We are all made of atoms…and only
atoms.
This includes
you and me!
Currently we
have about 115
kinds of atoms. In
the natural world
there exists 88
different kinds of
atoms.
The others have
been artificially
produced in
laboratories.
The Elements Song
Making stuff nature
never dreamed of.
We call each kind of atom an element,
and give it a specific name and symbol.
Copper
Gold
Cu
Au
Periodic Table
Abundance of
the elements, by
weight
The Earth’s interior is
rich in iron
Sand is made of
Silicon & Oxygen
The ocean
waters are made
of oxygen &
hydrogen
Atoms are made up of protons,
Of course real atoms
neutrons, and electrons.
don’t look anything like
this!
Protons and neutrons are found in
the nucleus of atoms -- roughly
at the center
Electrons
travel around
the nucleus.
Different kinds of atoms, or elements, are
different because they have different numbers of
protons.
They don’t look
anything like this
either!
We list the elements by
their atomic numbers the number of protons
they have.
Hydrogen, number 1
Helium, number 2
Physical Properties
• Physical properties: characteristics that
can be observed without changing the
identity of the substance.
• Examples:
–
–
–
–
–
–
mass
volume
color
shape
texture
density
Physical Changes
• Physical change: a change in the physical
form or properties of a substance that
occurs without a change in composition.
• Examples:
–
–
–
–
melting
freezing
grinding
dissolving
Chemical Properties
• Chemical property: describes a
substance’s ability to change into a
different substance.
• Examples:
– flammability
– reactivity
Chemical Changes
• Chemical change: occurs when a
substance changes composition by
forming one or more new
substances. (bonds are broken
and bonds are formed)
• Example:
– HCl + NaOH  NaCl + H2O
Indications of a Chemical Change…
Flames
Gas is given off (not to be confused with
boiling)
Color Change
Evaporation is a
physical change
Breaking is a physical
change.
Boiling is a change of
state, and therefore a
physical change!
Rusting is a Chemical
Change
Burning is a Chemical Change
Kinetic Theory
• All matter is made of atoms and
molecules that act like tiny particles.
• These tiny particles are always in
motion. The higher the temp., the
faster the particles move.
• At the same temp., more massive
(heavier) particles move slower than
less massive (lighter) particles.
SOLIDS
• Definite shape?
• YES
• Definite volume?
• YES
• Molecules in a solid are tightly packed and
constantly vibrating.
LIQUIDS
• Definite shape?
• NO
• Definite volume?
• YES
• Some liquids flow more easily than others.
The resistance of a liquid to flow is called
viscosity.
– Honey has a high viscosity compared to water.
GASES
• Definite shape?
• NO
• Definite volume?
• NO
• The particles in a gas are spread very far
apart, but can be compressed by pumping
them into a restricted volume.
Phase Changes
• Changes in phase are examples of physical
changes.
•
•
•
•
•
Melting: solid  liquid
Freezing: liquid  solid
Vaporization: liquid  gas
Condensation: gas  liquid
Sublimation: solid  gas
Changes of State
GAS
Vaporization
Sublimation
Condensation
Deposition
Melting
LIQUID
Melting
Freezing
SOLID
• ENERGY is the ability to change or move
matter.
• Energy is ABSORBED when substances
melt or evaporate.
– NOTE: our bodies cool down when our sweat
evaporates.
• Energy is RELEASED when substances
freeze or condense.
Melting
• The change of state from solid to liquid.
• Energy (heat) is absorbed by the
substance that is melting.
Freezing
• The change of state from liquid to solid.
Opposite of melting. Energy (heat) is
released by the substance undergoing
freezing.
•
Evaporation
The change of state at the surface of a liquid as it passes to a vapor.
This results from the random motion of molecules that occasionally
escape from the liquid surface.
– Energy (heat) is released by the liquid (Cooling of the liquid results)
– Can happen at any temperature
Condensation
• The change of state from gas to liquid. The opposite of
evaporation.
– Energy (heat) is absorbed by the liquid (Warming of the liquid
results)
Boiling
• Change from state from a liquid to a gas.
• Occurs throughout the liquid.
– boiling point/temperature is determined by pressure
– Energy (heat) is released by the liquid.
*Boiling & freezing points depend on the pressure.
Water at normal pressure (1 atm):
• For water at normal (every day) pressures:
• Melting/freezing point:
0 oC (32oF)
• Condensing/boiling point:
100 oC (212oF)
Label the points & temperatures on your graph.
Change the pressure  Change
the Boiling Point
Phase Diagrams
• a phase diagram shows the equilibria pressuretemperature relationship among the different
phases of a given substance
WATER
Carbon Dioxide
C
AB =
AC =
AD =
C
melting
AB =
curve
AC =
AD =
C
melting
AB =
curve
sublimation AD =
AC =
curve
C
melting
AB =
curve
vapor
sublimation AD = pressure
AC =
curve
curve
C
A
triple point = Point ______
The point at which all 3 phases of a substance (solid, liquid, gas) can
coexist at equilibrium.
D
critical point = Point ______
The combination of critical temperature and critical pressure.
critical temp = temp. above which a gas cannot be liquefied. (H2O=374ºC)
critical pressure = press. required to liquefy a gas at its critical temperature. (H2O=218
atm)
Conditions for H2O on other planets…