Download Chem 11, Notes – Unit 3 – Properties of Matter

Chemistry 11
Properties of Substances
Definitions in Science
What is the difference between a hypothesis, a
theory, and a law?
• A hypothesis is a statement that is unproven that
is yet to be tested
• A theory is a set of hypotheses that come from
observations from the natural world
o A theory has been repeatedly tested and is
widely accepted  explains phenomena
• A law will state the results of experiments and
state what will happen in specific situations
o A law will not explain phenomena
What is the difference between an observation and
an interpretation?
• When you observe, you are using your senses to
collect data
• When you make an interpretation, you are
putting meaning to your observations
Chemistry 11
Properties of Substances
Physical Properties of Matter
What is the difference between a physical and
chemical property?
• A physical property of a pure substance is
anything that can be observed without changing
the identity of the substance
o An intensive physical property depends
upon the nature of the substance
o An extensive physical property depends on
the amount of substance present
• A chemical property is a characteristic which is
exhibited as one substance is chemically
transformed into another
What is matter made up of?
• Matter consists of three states:
o Solid – particles that are very ordered and
are not able to compress
o Liquid – particles with greater kinetic
energy than solids and are not able to
compress
Chemistry 11
Properties of Substances
o Gas – particles with wide separation and are
able to compress
How can we classify matter?
• There are two classification schemes
o Classification by phase  see Hebden p. 50
o Classification by composition  see
Classification of Matter handout
How can we separate a mixture?
• We look at the property of each substance and
use those properties to separate substances
o Hand separation/filtration  particle size
o Evaporation/distillation  boiling point
o Solvent extraction/recrystallization 
differing solubilities
o Gravity separation  density
o Chromatography  differing solubilities
Chemistry 11
Properties of Substances
Phase Change Diagrams
What happens when a substance goes through a
physical change?
• In a chemical change, new substances are
formed
• In a physical change, the phase of a substance
changes
• When a substance changes phase, energy is
added (heating) or removed (cooling)
• When a substance cools, the substance exhibits
this behaviour
Temperature 
g
l
s
Time 
Chemistry 11
Properties of Substances
On the sloping portion of the graph  energy is
removed from the substance as it cools
• On the plateaus  energy removed is used to
change phase so temperature does not decrease
• On the plateau portions, the substance is in
transition phase between phases
•
What happens to the molecules through a phase
change?
• Molecules are constantly in motion
• As a substance is heated, the amount of energy
present in the molecules increase
• The three types of kinetic energy a molecule can
possess are
o Rotational energy – energy which causes a
molecule to rotate about an axis (frisbee)
o Vibrational energy – energy which causes
the length of a bond to change (slinky toy)
o Translational energy – energy which causes
a molecule to move about in space (thrown
ball)
Chemistry 11
Properties of Substances
• When a substance is heated, translational energy
causes bonds to break which hold a substance
together
• As a substance is continually heated, all three
types of energy increase, but it is the increase in
translational energy that allows for a phase
change
Chemistry 11
Properties of Substances
What occurs at the plateaus?
• When a substance is being heated or cooled,
there is a part of the curve that plateaus
• These plateaus indicates a constant temperature
where an intensive property of the substance is
displayed
• Boiling point: the temperature where a
substance changes from a liquid to a gas
• Freezing point: the temperature where a
substance changes from a liquid to a solid
• Melting point: the temperature where a
substance changes from solid to a liquid
Note: these changes and properties are applicable
only to physical changes  a chemical change
occurs when a new substance with new properties
results
Physical change: water is heated from liquid form to
form steam
Chemical change: water is electrolysed and
separated into oxygen gas and hydrogen gas