Matter
Anything that takes up space (has a
volume) and has mass!
Substances
A substance has a uniform and definite
composition.
• Elements are the simplest form of matter
which cannot be broken down chemically.
• Compounds are made up of two or more
elements that are chemically combined in a
fixed ratio.
Elements
It is the simplest form of matter that can exist under
lab conditions.
• Elements cannot be separated into simpler
substances.
• They are represented by a symbol; ONE Capital
Letter. (Each capital letter represents one
element.) Sometimes a lowercase letter is used as
well.
• Elements are shown on the Periodic Table
• There are some elements that exist in nature only
as diatomic elements. Br2, I2, N2, Cl2, H2, O2, F2
Compounds
Two or more elements chemically combined with each other.
• Compounds can be separated into simpler substances.
• A compound has a fixed composition. It is always the same.
• Formulas for compounds are written in a certain way.
EXAMPLES: H2O
CO2
NaCl
• The little numbers directly following an element symbol are
called subscripts. This tells you how many atoms of that
element are in the compound.
• EXAMPLES: H2O
CO2
NaCl
(2 H’s and 1 O)
(1 C and 2 O’s)
(1 Na and 1 Cl)
Mixtures
A mixture is comprised of two or more
substances.
• Homogeneous: a uniform mixture also known
as a solution. You can not see its parts.
Sometimes gets the symbol (aq) for aqueous.
• Heterogeneous: non uniform mixture. You can
see the parts.
Homogeneous or Heterogeneous?
Element, Compound or Mixture?
Iron
Air
Water (tap)
Water (purified)
Gold
Methane
Sand
Sugar
Iced tea
Steel
Chlorine
Salt
Soap
Brass
Sodium
Calcium carbonate
Separating Mixtures
• There are many ways to separate a mixture. If it is
heterogeneous, you many be able to just sort them
with your hands. If not, you can use:
1. Decanting: The least accurate way to separate; you
can pour off the top layer of liquid from the bottom
layer. (You have probably done this at the beach with
water and sand mixtures.)
2. Filtering: To separate a solid from a liquid, filter it
using a funnel and filter paper. The solid stays on top,
liquids pour through. (What happens if the solid is
completely dissolved in the liquid?)
Decant/ Filter
Separating Mixtures
3. Distillation: When two or more liquids are
mixed homogeneously, you can boil off each
liquid separately using the following
This is how
apparatus:
many water
bottling
companies
clean their
water.
Solids Liquids and Gases
Solids
•
•
•
•
Definite shape
Definite volume
Constant vibration
Molecules are packed
tightly in a geometric
(crystalline) pattern
Liquids
•
•
•
•
•
No definite shape
Definite volume
Constant motion
No arrangement
Molecules are closer
together than a gas but
further than a solid
Gases
•
•
•
•
•
No definite shape
No definite volume
No arrangement
Spread out
Compressable
Pressure
• Gases exert a pressure on
surrounding substances
because they are constantly
moving and colliding with
other surfaces.
• Only in a vacuum, where
there are no molecules,
there is no pressure.
• Gas pressure can be
measured in atmospheres
or kilopascals, according to
reference table A.
1.
2.
3.
4.
5.
6.
7.
Which represents a liquid? Solid? Gas?
Which has the highest melting point?
Which has the weakest IMF?
Which has the lowest boiling point?
Which has the strongest IMF?
Which has a definite shape?
Which have a definite volume?
What is a vapor?
• Vapors are the gaseous form of a substance
that is normally a liquid or solid at room
temperature.
Heat
• Endothermic reaction require you to
put heat in.
• Exothermic reactions require you to
take heat out; heat exits.
Phase Changes
Identify the phase change and if it’s
endothermic or exothermic:
• Evaporation
Liquid to gas
endothermic
• Condensation
Gas to liquid
exothermic
• Melting
Solid to liquid endothermic
• Freezing
Liquid to solid exothermic
• Sublimation
Solid to gas
endothermic
• Deposition
gas to solid
exothermic
Describe the following:
• Melting point
• Boiling Point
• Freezing Point
Thermochemistry
• The study of energy changes that occur in
chemical reactions.
– Kinetic energy refers to energy of motion.
(Temperature)
– Potential Energy refers to stored energy.
Phase Change Diagrams
Where is the KE increasing? Where is the PE increasing? Where is
KE stable? Where is the melting and boiling point?
D
B
A
C
E
1. Which line segment
represents a liquid? A
solid?
2. What is the boiling point?
3. What is the freezing point?
4. On what line segments is
the PE increasing?
5. What is PE doing when it is
not increasing?
6. Describe KE and PE.
7. Where is the solid/liquid
equilibrium?
8. What would happen if it
was heated further?
Cooling Curve
A
C
B
E
D
F
Identify the lines for solid, liquid and gas.
Where is the KE decreasing? Where is the PE decreasing? Where is
PE stable? Where is the melting and boiling point?
A student heats an unknown pure
solid until it remains a gas and
obtains the following data:
1. Draw and label a graph with time on
the x axis and temperature on the y
axis.
2. What is the freezing point?
3. What is the boiling point?
4. At what time do you first see a sign of
the liquid phase?
5. At what time do you last see a sign of
the liquid phase?
6. Explain what would happen if the
student continued heating for another
30s.
Time
(s)
Temp (C)
0
0
30
10
60
20
90
20
120
20
150
30
180
40
210
50
240
50
270
50
300
50
330
50
360
60
Changes in the Lab
• Physical Changes require that the chemical
not change composition. (Breaking, grinding,
etc.)
• Chemical Changes require that the chemical
changes into a new substance. (Burning,
reacting, etc.)
Physical or Chemical Changes?