Physical and Chemical Changes
Pure Substances
Mixtures
States of Matter
Everything that has mass and
volume is called matter.
There is no observable change
in the quantity of matter
during a chemical reaction or a
physical change.
In other words, matter cannot
be created nor destroyed. It is
just converted from one form
to another
•Have a definite shape
•Have a definite volume
•Particles of solids are
tightly packed, vibrating
about a fixed position.
Have an indefinite shape
Have a definite volume
Particles of liquids are tightly
packed, but are far enough apart to
slide over one another.
•Have an indefinite shape
•Have an indefinite volume
Particles of gases are very far apart and move
freely.
Changing States of Matter
Boiling point and melting point
 The melting point is the temperature at which a solid
turns into a liquid. This is also the freezing point. Ex.
At 0ºC ice melts into water and water freezes into ice.
 The boiling point is the temperature at which a liquid
turns into a vapor. This is also the condensation point.
Ex. At 100ºC, water boils and becomes vapor and water
vapor condenses into liquid.
Added heat
What are phase changes
called?
All matter, regardless of state,
undergoes physical and
chemical changes. These
changes can be microscopic or
macroscopic.
Measuring Matter
 How can we measure matter?
 What equipment would we need?
Mass and Weight
 Are they the same?
 What happens to our mass and weight if we were to go
to the moon?
 If two substances have the same weight, do they have
the same mass?
Measuring Mass
 Mass: Amount of substance
 How can we measure mass?
 Scale or balance
 What are the units of mass?
 Grams (or pounds)
Measuring Volume
 Volume: Amount of space a substance takes up
 How can we measure (or calculate) volume?
 measuring cup, graduated cylinder, (ruler)
 What are the units of volume?
 mL, L, cm3, in3
Water Displacement
• Volume = change in water level
• Volume of water with object − volume of water alone
 If two substances have the same volume, will they
displace the same amount of water?
Do We Have Gold?
 How could we use mass and volume to prove if our
golden penny is really gold?
Discover Density
 Density: How much stuff is in a certain space
 D= m/V
m
D
V
To determine the density of a substance, divide its
mass by its volume.
To solve for volume, divide mass by density.
To solve for mass, multiply density by volume.
A substance changes
state but does not change
its chemical composition.
•For example: water freezing,
cutting a piece of wood
• The form or appearance
has changed, but the
properties of that
substance are the same
A substance changes into something new.
Occurs due to heating/chemical
reaction
 The common signs of a chemical change
are:
Bubbles forming
Heat is given off, or taken in
Mass changed
Color change
http://www.brainpop.com/science/matterandch
emistry/propertychanges/
Physical and chemical
properties may be intensive
or extensive.
 intensive properties do not depend on
the size of the sample of matter and
can be used to identify substances.
 Density
 Color
 Boiling Point
 Melting Point
extensive properties DO depend
on the quantity of the sample.
Mass
volume
 Physical properties are those that we can
determine/observe without changing the
identity of the substance we are studying.
 Examples: Hardness, color, density,
melting/boiling point
 Chemical properties describe the way a substance
can change or react to form other substances.
 Any of a material’s properties that become evident
during a chemical reaction
 In other words, we have to define chemical
properties of a substance by the chemical changes
it undergoes…the substance’s internal structure
must be altered for these properties to be observed
 Ex: Heat of combustion, reactivity w/ water
Substances can be identified as either
an element, compound, or a mixture.
Compounds
Elements
 Can be decomposed into
simpler substances by
chemical changes, always
in a definite ratio (combo
of two or more elements)
 H2O ; H2O2  Hydrogen ;
Oxygen
 Cannot be decomposed
into simpler substances
by chemical changes
 Fixed composition
 Cannot be separated into simpler
substances by physical methods
Ex: You can’t separate the H from the O in
H2O2 without a chemical change
 Can only be changed in identity
and properties by chemical
methods
 Properties do not vary
Mixtures are two or more substances that are NOT chemically
combined – Can be separated by physical means or chemical
means (sometimes) ; i.e. Sieve (physical) or Column
Chromatography (chemical)
Mixtures do not:

Have constant boiling points

Have constant melting points
 Have variable composition
 Components retain their individual
characteristic properties (i.e. Sand/Salt
Mixture: sand and salt retain their individual BPs,
MPs, etc.)
 May be separated into pure substances by
physical or chemical methods – Mostly
PHYSICAL
 Mixtures of different compositions may
have widely different properties
EX: imagine a handful of M&Ms as an examples – or … a
handful of different types of beans:
 Have the same composition throughout
 Components are indistinguishable
 Liquid: Looks like a single, uniform liquid
 Solid: An Alloy – Stainless steel(Iron, Chromium, others…)
 May or may not scatter light
Examples: Kool-Aid, shampoo, etc.
Solutions are homogeneous mixtures that do not
scatter light. (exception: COLLOIDS)
Created when something is completely dissolved in pure
water. Therefore, they are easily separated by distillation
or evaporation.
Examples: Kool-Aid, salt water
Colloids are solutions.
Substance that is microscopically dispersed in
another substance
They can be described as a substance trapped inside
another substance
They can be identified by their characteristic
scattering of light.
For example: jello, fog, smoke, milk, vanilla
yogurt
Milk  a colloid of liquid butterfat globules
dispersed within a water-based solution
 Do not have same composition
throughout
 Components are distinguishable
Examples: fruit salad, vegetable soup,
etc.
 Suspensions are mixtures that do not stay mixed
 The solute settles or can be filtered out
 Examples: lava lamp, snow globes
Table 2.1 (pg 40)
Substance
State
Color
M.P. (°C)
B. P. (°C)
Neon
Gas
colorless
-249
-246
Oxygen
Gas
Colorless
-218
-183
Chlorine
Gas
Greenish-yellow
-101
-34
Ethanol
Liquid
Colorless
-117
78
Mercury
Liquid
Silvery-white
-39
357
Bromine
Liquid
Reddish-brown
-7
59
Water
Liquid
Colorless
0
100
Sulfur
Solid
Yellow
115
445
Sodium chloride
Solid
White
801
1413
Gold
Solid
Yellow
1064
2856
Copper
Solid
Reddish-yellow
1084
2562