Chemistry
Ms. Piela

A property of a substance that can be
measured or observed without
changing its composition
◦ Examples
 Size/Shape
 Density
 Mass
 Melting point/Boiling point/
Freezing point

Any change that occurs to a substance
that does not change its chemical
composition
◦ Examples
 Cutting
 Breaking
 Melting
 Boiling

Intensive: does NOT depend on how much
substance there is
◦ Density
◦ Color

Extensive: DOES depend on how much
substance there is
◦ Weight
◦ Length
 Example
◦ Which of the following are
physical changes? (Circle all that
apply)
a) Making caramel from sugar
b) Carving a wooden figure
c) Freezing mercury
d) dissolving salt in water

A property of a substance that can be
measured or observed and changes its
composition
◦ Examples
 Reactivity
 Water
 Oxygen
 pH
 For
chemical changes to occur, a
chemical reaction must take place
 Chemical
reactions are the
rearrangement of atoms and
molecules that forms new
substances
 Example:
CH4 + 2 O2 → CO2 + 2 H2O

Demo Example: Burning Magnesium
2 Mg + O2
→ 2 MgO
◦ Reactants are the initial substances before a
reaction
◦ Products are substance formed in a reaction

Chemical change is any change in
chemical composition that forms a new
substance
◦ Examples
 Rusting
 Decomposing compost
 Evolution
of a gas
 Formation of a precipitate
◦ Precipitates are solids that form in a
solution
 Release
or absorption of energy
◦ i.e. heat released, light given off,
sound
 Color
change in a reaction system
 Practice
Problem #1
◦ Which of the following are
chemical changes and which are
physical changes?
a) Cracking an egg
b)Removing a stain with bleach
c) Burning a candle
d)Melting butter

Practice Problem #2
◦ For the following, identify them as
chemical property, chemical change,
physical property, or physical change:
a) Decomposition of mercury (II) oxide
b) Iron reacts with oxygen, while gold
does not
c) Oxygen is colorless, odorless, and
soluble (dissolves) in water
d) Under extreme pressures, oxygen will
liquefy
Chemical Changes
•Any change that forms a new substance
•Example: Burning, Decomposing
Physical Changes
•Any change that does not change the
chemical makeup of the substance
•Example: Cutting, Melting
 What
is matter?
◦ Anything that has mass and takes up
space
◦ Examples:
 Desks
 Air
 Lazy Students
 Insane Science Teachers

Solids
◦ have definite shape and definite volume
 Example
 Diamonds
◦ Particles are slow and will vibrate in place

Liquids
◦ have indefinite shape and definite volume
 Example
 Water
◦ Particles move faster and slide past one another

Gases
◦ Have indefinite
shape and
indefinite volume
◦ Example
 Air
◦ Particles move
fast with large
spaces in between
Solids
Liquids
Gases
Definite
Shape
Indefinite
Shape
Indefinite
Shape
Definite
Volume
Definite
Volume
Indefinite
Volume
Particles
vibrate in
place
Particles
slide past
one another
Particles
move freely
Matter
Pure
Substances
Element
Compound
Mixtures
Homogeneous
Heterogeneous

Pure substances are substances that
contain only one kind of matter
◦ Example
 Water (H2O), Oxygen (O2), Iron (Fe)

Mixtures are physical blends of one or
more pure substances
◦ Example
 Salad, Soup
Matter
Pure
Substances
Element
Compound
Mixture
Homogeneous
Heterogeneous

Homogeneous mixtures are mixtures
with uniform composition
◦ Examples: Milk, Gas, Air

Heterogeneous mixtures are mixtures
that do not have uniform composition
◦ Examples: Salad, Soup
Matter
Pure Substances
Element
Compound
Mixture
Homogeneous
Heterogeneous
 Example
Problem
◦ Determine whether the following
examples are heterogeneous
mixtures or homogeneous mixtures
a) Stainless steel
b) Italian Dressing
c) Maple syrup
d) Chocolate chip cookie

Elements are the simplest form of
matter
◦ Examples: Carbon (C), Gold (Au), Mercury (Hg)

Compounds are two or more elements
chemically combined
◦ Examples:
Water (H2O), Sugar (C6H12O6)
(not O2, N2)
Matter
Pure
Substances
Element
Compound
Mixture
Homogeneous
Heterogeneous

Practice #1
a)
b)
c)
d)
e)
f)

CH4 Compound
S8 Element
Concrete Heterogeneous
Distilled water Compound
Salt water Homogeneous
CH2O Compound
Practice #2
◦ Mixture. A physical blend of two substances

Practice #3
◦ Blue solid is compound. Can’t determine others