Session 27 Do Now
Open your book to the periodic table.
1. Find five elements with symbols that match
(oxygen, O) and list the names and symbols
2. Find five elements with symbols that don’t
match (potassium, K) and list the names and
symbols
3. What do you think? Which elements were
discovered earlier (matching or unmatching)
Why?
Session 28 Do Now
Give examples of the following and label
each one:
1.
2.
3.
4.
5.
6.
7.
8.
Element
Compound
Solution
Heterogeneous mixture
Physical property
Chemical property
Physical change
Chemical change
Part A—Types of Matter
Matter can be classified
Matter
Pure
Substances
Element
Compound
Mixtures
Homogeneous
(Solutions)
Heterogeneous
Matter
Anything that has mass and takes up
space
Anything made from atoms
Examples:
Molecules
Cells
People
Air
Water
Pure Substances versus Mixtures
Matter is classified as either a pure substance or a mixture
Pure Substances
Mixtures
Every piece of
matter is the same
More than one type
of matter mixed
together
Elements versus Compounds
Pure substances are either elements or compounds
Elements
Compound
Every atom is the
same type of atom
More than one type
of atom chemically
bonded together.
Every molecule is
the same.
Elements
Single Atom
Element
Cannot be separated by
chemical or physical
processes
Pure substance
Every atom is the same
Elements can be found on the periodic table!
Compounds
Single Molecule
Made of more than one type of
atom bonded together
Compound
Pure substance
Every molecule is the same
Can be separated by chemical
reactions only
Mixtures
Mixtures can be classified as homogeneous or heterogeneous
Homogeneous
(aka “solution”)
Heterogeneous
It looks the same
throughout
Different matter can
be seen (chunks,
bubbles, floaties,
layers, etc.)
Mixtures
>1 different
type of matter
Can be separated
physically
Mixture
Not a pure substance
Physical combination of more
than 1 type of pure substance
Let’s Practice
Example:
Determine if
each is
element,
compound,
homogeneous
or
heterogeneous
mixtures
Tin foil
Copper pipe
Concrete
Carbon tetrachloride
Sports drink
Let’s Practice
Example:
Determine if
each is
element,
compound,
homogeneous
or
heterogeneous
mixtures
Tin foil
Element
Copper pipe
Element
Concrete
Heterogeneous mix
Carbon tetrachloride
Compound
Sports drink
Homogenous mix
Part B —States of Matter
Solid
 Closely packed together particles
 Vibrate in place
 Can’t switch places
 Definite shape
 Definite volume
Liquid
 Particles more spread out than solid
 Particles are free to move past each other
 Not compressible
 Definite volume
 No definite shape – take shape of container
Gas
 Particles very spread out
 Rapid, random motion
 Highly compressible
 No definite volume—they will fill container
 No definite shape—take shape of container
Increasing molecular motion (temperature)
Changes in State
Sublimation
Boiling or
Evaporating
Liquid
Melting
Gas
Condensing
Freezing
Solid
Deposition
Temperature of state changes
Freezing point = melting point
Boiling point = condensation point
What’s between the particles?
?
Nothing! There is absolutely nothing between the particles!
Part C—Properties of Matter
Physical versus Chemical Properties
Physical Property
Chemical Property
Can be observed
or tested without
changing the
atoms or molecules
In the process of
observing or
testing, the atoms
or molecules are
changed into
different
substance(s)
Let’s Practice
Flammability
Example:
Are the
following
properties are
physical or
chemical?
Boiling point
Solubility
Malleability
Reactivity with oxygen
Let’s Practice
Example:
Are the
following
properties are
physical or
chemical?
Flammability
Chemical
Boiling point
Physical
Solubility
Physical
Malleability
Physical
Reactivity with oxygen Chemical
Part D—Density
Definitions
Density- the ratio of mass to volume of
a sample
How heavy is it for its size?
Lead = high density…small size is very heavy
Air = low density…large sample has very little mass
Density
Mass
Density
In grams (g)
In g/L or g/mL
D=
m
V
Volume
In liters (L) or mL
Don’t try to cancel out the units…density has “2 units” – a
mass unit over a volume unit!
Example 1—Solving for Density
D =?
Example:
What is the
density of a
sample with a
mass of 2.50 g
and a volume
of 1.7 mL?
m
D
V
m = 2.50 g
V = 1.7 mL
2.50 g
D
1.7 mL
g
D  1.5
mL
Example 2—Solving for Mass
m=?
V = 2.34 mL
Example:
What is the
mass of a 2.34
mL sample with
a density of
2.78 g/mL?
D = 2.78 g/mL
2.34 mL ×
2.78 g
m
D
V
m

mL 2.34mL
m  6.51g
× 2.34 mL
Example 3—Solving for Volume
m = 45.4 g
Example:
A sample is
45.4 g and has
a density of
0.87 g/mL.
What is the
volume?
V  0.87 g
0.87 g/mL
m
D
V
D = 0.87 g/mL
V=?
V×
mL
0.87 g
 45.4 g
0.87 g/mL
mL

45.4 g
V
×V
V  52mL
Floating
Objects float when they are less dense
than the substance they are in!
Fewer particles in the
same space = less
dense
More particles in the
same space = More
dense
Let’s Practice 1
m = 22.7 g
Example:
If a 22.7 g
sample has a
volume of 47.8
mL, will it float
in water?
m
D
V
V = 47.8 mL
D=?
22.7 g
D
47.8mL
D  0.475 g
mL
The density of water is 1 g/mL. This sample’s density is lower. It will float.
Part E—Changes in Matter
Definition
Physical Change - n. Change in which
the chemical structure of the
substances is not changed.
Chemical Change - n. Change in which
the chemical structures of the
substances are changed.
Physical & Chemical Changes
Physical changes do not produce new
substances
breaking, dissolving, distilling, cutting, etc.
Changes in state are physical changes (boiling,
condensing, melting and freezing)
Chemical changes do produce new
substances
rusting, burning, metabolizing food, oxidation or
reduction, reacting with oxygen, etc.
Possible Signs of Chemical Changes
Gas production (bubbling)
Energy change (getting hot or cold)
Color change
Light given off
Formation of a solid
Physical & Chemical Changes
Also…if a change can be un-done by a physical change,
then the original change was physical as well.
If salt is dissolved in water, it seems to disappear…
many people think this is a chemical change.
But if the water is evaporated (a physical change), the salt
is left in the container.
Since the original change was un-done with a physical
change, then the original change (the dissolving) was a
physical change as well.
Confusing changes
People often use the following terms incorrectly.
Term
Definition
Type of
Change
Melting
Changes a solid into a
liquid
Physical
Burning
Reacting with oxygen to
produce CO2 and H2O
Chemical
Dissolving
Adding one substance
to another to form a
homogeneous mixture
Heating a sample to
evaporate the water
Physical
Drying
Physical
Part F—Endothermic and
Exothermic
Endothermic & Exothermic
When the system absorbs energy from the
surroundings, it’s an endothermic process
When the system releases energy to the
surroundings, it’s an exothermic process
Exothermic & You
You touch the beaker and it feels
hot
Energy is being transferred TO YOU
You are the surroundings
When energy moves from system to
surroundings, it’s exothermic
Exothermic
If the container feels hot to you, energy is
being transferred TO YOU (the
surroundings) from the system—
exothermic
Endothermic
The opposite is also true
If the container feels cold to you, energy is
being transferred FROM YOU (the
surroundings) into the system—
endothermic
Let’s Practice
Example:
Identify the system
and surroundings
when you hold an
ice cube while it
melts. Is this endoor exothermic?
System: Water molecules in the form of ice
Surroundings: You and the air
It feels cold to you…so energy is leaving you (surroundings)
When energy goes from surroundings to system it’s endothermic