Transcript Physical or Chemical Change? - Mrs. Storer Science Website

Physical
and Chemical
Properties and
Changes
Mrs. Storer
Chemistry
Physical versus
Chemical Properties
MATTER
• Matter: anything that has mass and takes up
space
• Mass – the amount of matter in something
• Volume – the amount of space something occupies
• Which of the following is matter?
• A car?
• A box?
• You?
What is a property?
• Property: a
characteristic of
a substance
that can be
observed.
Physical Property
Physical property: a property that can be
observed without chemically changing the
matter. These are usually physical
descriptions of the material, but they can
also include some behaviors.
•
Physical properties can be
used to separate mixtures!
Physical Properties
Examples:
Color
Shape
Size (volume)
Texture
Melting point
Boiling point
Mass
Weight
Luster
Specific heat
Solubility
Elasticity
Phase
Density (more on this
later)
Physical Properties Behaviors
Examples:
Malleability: the ability to Ductility: the ability to be
be hammered into a thin stretched into a wire
sheet
Magnetic = attraction of a Viscosity: the resistance
magnet to iron
of a fluid to flow
Buoyancy: ability of a
substance to float
Extensive vs Intensive Properties
Physical properties can be described as:
•Extensive – dependent on the amount
of the substance
• Examples: mass, length, volume
•Intensive – independent on the amount
• Examples: density, scent
Demo: float two pieces of wood of different lengths
Special Physical Properties
• Melting point: the temperature at which
a substance changes from a solid to a
liquid at a given pressure
water = 0oC
• Boiling point: the temperature at which
a substance changes from a liquid to a
gas at a given pressure
water = 100oC
Chemical Properties
• Chemical property: describes how a
substance interacts with other
substances.
Examples:
Flammabilty
Ability to rust
Reactivity
Combustability
Acidity
Basicity
FLAMMABILITY: A material’s ability
to BURN in the presence of OXYGEN
REACTIVITY:
How readily (easily) a substance
combines chemically with other
substances.
Which has higher reactivity?
A 14 karat gold ring or a cheap metal
ring from the vending machine at the
grocery store?
What is your evidence?
Physical and Chemical Change
Matter can change in two
different ways
1. Physical Change
2. Chemical Change
(1) Physical Change
Physical changes are those
changes that do not result in
the production of a new
substance.
If you melt a block of ice, you
still have H2O at the end of the
change.
(1) Physical Change
Signs of physical change include:
• Changing the shape or size
• Dissolving
• State change
Phases of Matter
Phase
Solids
Shape
Volume
Definite shape
Definite volume
Particles packed together
Liquids
Indefinite shape
Definite volume
Particles have room to move around
Gases
Indefinite shape
Particles far apart
Indefinite volume
Common examples of physical
changes are:
melting
freezing
condensing
breaking
crushing
cutting
bending
Some, but not all physical
changes can be reversed. You
could refreeze the water into
ice, but you cannot put your
hair back together if you don’t
like your haircut!
(2) Chemical Change
Chemical changes, or
chemical reactions, are
changes that result in the
production of one or more
new substances.
Chemical Change
Signs of a chemical change
include:
•gas bubbles
•color change - leaves turning colors in
the fall, rust appearing
•disappearance of color – fading fabric
•heat or light
When you burn a log in a fireplace,
you are carrying out a chemical
reaction that releases
carbon. When you light your
Bunsen burner in lab, you are
carrying out a chemical reaction
that produces water and carbon
dioxide.
Common examples of
chemical changes:
digestion
photosynthesis
decomposition
rusting
respiration
burning
tarnishing
Light
6CO2 + 6H2O  C6H12O6 + 6O2
Light Energy
CO2 + H2O
Chloroplast
Sugars + O2
Chemical Change:
Cleaning tarnished silver
Tarnish is silver sulfides that form from sulfur
compounds in the air

Only sure proof that a new substance is
produced is a rapid release of energy –
heat, light, and sound
WEATHERING – CHEMICAL OR PHYSICAL CHANGE?
= BOTH
Forces of nature reshape Earth’s surface
Physical:
Large rocks split when water freezes
Doesn’t change the rock
Streams cut through softer rock
Canyons
Chemical:
Solid Calcium Carbonate, found in limestone,
doesn’t dissolve easily
React with
acid (rain)
White Cliffs
of Dover
Changes to a new substance (Calcium Hydrogen Carbonate)
This does dissolve with water
Caves = stalactites and stalagmites
Law of Conservation of Mass
Amongst all of this change,
remember that
Mass cannot be created nor
destroyed.
Let’s practice
Number your paper from 115 and write if it is a
physical or chemical
change
Physical or Chemical Change?
1. Painting wood
2. Burning paper
3. Digestion of food
4. Sugar dissolving in water
5. Iron turning red when heated
6. Evaporation
7. Pond freezing in winter
Physical or Chemical Change?
8. Cutting wire
9. Painting fingernails
10.Cutting fabric
11.Baking muffins
12.Shattering glass
13.Decomposition of old leaves
14.Wrinkling of a shirt
15.Old nail rusting
Physical or Chemical Change?
•Painting Wood
•PHYSICAL
Physical or Chemical Change?
• Burning Paper
• CHEMICAL
Physical or Chemical Change?
• Digestion of food
• CHEMICAL
Physical or Chemical Change?
• Sugar dissolving in
water
• PHYSICAL
Physical or Chemical Change?
• Iron turning red when
heated
• PHYSICAL
Physical or Chemical Change?
• Evaporation
• PHYSICAL
Physical or Chemical Change?
• A pond freezing in
winter
• PHYSICAL
Physical or Chemical Change?
• Cutting wire
• PHYSICAL
Physical or Chemical Change?
• Painting fingernails
• PHYSICAL
Physical or Chemical Change?
• Cutting fabric
• PHYSICAL
Physical or Chemical Change?
• Baking muffins
• CHEMICAL
Physical or Chemical Change?
• Shattering glass
• PHYSICAL
Physical or Chemical Change?
• Decomposition of old
leaves
• CHEMICAL
Physical or Chemical Change?
• Wrinkling a shirt
• PHYSICAL
Physical or Chemical Change?
• An old nail rusting
• CHEMICAL
Physical or Chemical Property?
Combustibility
CP
Density
PP
Malleability
PP
CP
Weight
PP
Tendency to
corrode
Volume
Failure to react CP
Melting point
PP
Ductility
PP
Odor
PP
Texture
PP
Flammability
CP
PP
Physical or Chemical Change?
Digestion of food CC
Explosions
CC
Getting a haircut PP
Lighting a candle
CC
Evaporation
PC
Tarnishing silver
CP
Ice cube melting
PP
Formation of acid
rain
CP
Crushing rocks
PP
Dissolving salt in
water
PP