Physical Properties
Physical Property :
Characteristic of a material that can be
observed or measured without changing the
composition of the substances in the material.

– Examples:
– Viscosity
– conductivity
– malleability
– hardness
– melting point
– boiling point
– density
Examples of Physical Properties
Viscosity –
Tendency of a liquid to
keep from flowing
Thick liquids  high
viscosity.
• Thin liquids  low
viscosity.
•
Examples of Physical Properties
Conductivity Ability to allow heat or electricity to flow
Materials that have a high conductivity, such
as metals, are called conductors.
• Good conductors of heat are usually also
good conductors of electricity.
•
Examples of Physical Properties
Malleability The ability of a solid to be hammered without
shattering
•

Most metals, such as gold, are malleable.
Solids that shatter when struck are brittle, not
malleable.
•
An ice cube or piece of glass breaks into small pieces
when struck with a hammer.
Examples of Physical Properties
Hardness - resistance to scratching
One material can scratch another material if it is
harder than the other material.
Examples:
• A kitchen knife can scratch a copper sheet
because stainless steel is harder than
copper.
• The material used to sharpen the knife
blade must be harder than stainless steel.
• Diamond is the hardest known material.
Examples of Physical Properties
Melting and Boiling Points Temperature at which material changes state
• Melting point (freezing is same temperature)
 Melting  solid to liquid
 Freezing  liquid to solid
•
Boiling point (condensing is same temperature)
 Boiling  liquid to gas
 Condensing  gas to liquid
Examples of Physical Properties
Density –
the ratio of the mass of a substance to its
volume (i.e. mass/volume)
Characteristic Property
• Density can be used to test the purity of a
substance.
• Silver has a density of 10.5 g/cm3. A coin with a
density of 9.9 g/cm3 is not made from silver, or
it contains substances in addition to silver.
•
Examples of Physical Properties
Physical properties are used to:
•Identify materials
•Choose materials for a specific purpose
•Separate the substances in mixtures.
Using Properties to Separate Mixtures
•

Filtration and distillation are
two common separation
methods.
Distillation – separates the
substances in a solution based
on their boiling points.
Examples: gasoline, moonshine
Recognizing Physical Changes
Physical change:
Substances in the material remain the same.
Some of the properties of a material change,
properties such as: Size, Shape, State of matter
(solid, liquid, or gas)
Examples include:
Water
going from a liquid to a gas during boiling
Melting butter in a pan
Crumpling a piece of paper
Slicing a tomato
Some but not all physical changes can be
reversed.
Braiding
hair is a reversible change.
Cutting hair cannot be reversed.
Both are physical changes.
Chemical Properties

As a candle burns, its compounds combine with
oxygen in the air to form water and carbon
dioxide.
Chemical property –
ability to produce a change in the
composition of matter.
Examples:
 Flammability
 Reactivity

Chemical Properties

Flammability


A material’s ability to burn in the presence of
oxygen.
 Materials that burn can be used as fuel.
Reactivity

How readily a substance combines chemically
with other substances
Chemical Change
Rust forms when oxygen reacts with iron and water.
Rust is a brittle, reddish-brown compound. Because
iron is highly reactive, you would not choose iron to
make jewelry or coins.
Recognizing Chemical Change
A
chemical change occurs when a substance
reacts and forms one or more new
substances.
Example:

The color change in a banana peel is caused by
chemical changes that are taking place in the
cells of the banana.
Recognizing Chemical Change
 3 common types of evidence for a
chemical change:
•Change in color
•Production of a gas
•Formation of a precipitate.
Recognizing Chemical Change
Change in Color – a clue that a chemical
change may have produced at least one new
substance.
Examples:
• A shiny silver bracelet that is exposed to air will
darken.
• As a match burns, it shrivels up and turns black.
• A new copper roof and an old copper roof have
different colors.
Recognizing Chemical Change


A new copper roof has a reddish color.
The green patina on an old copper roof
is a mixture of copper compounds.
Recognizing Chemical Change
Production of a Gas
Vinegar
+ Baking Soda  bubbles of carbon dioxide
form immediately.
A similar chemical change happens when you use
baking powder as an ingredient in a cake recipe.
 Bubbles of carbon dioxide expand and cause the
cake to rise.
Recognizing Chemical Change
Formation of a Precipitate


Precipitate – any solid that forms and separates
from a liquid mixture.
Example:

When an acid is added to milk, proteins in the milk
undergo a chemical change that causes them to stick
together in clumps and form a precipitate  cottage
cheese.
Chemical Changes

Color change, a gas, or a precipitate DO
NOT guarantee that a chemical change has
taken place.

When an iron horseshoe is heated, its color
changes from gray to red, but the iron is still
iron. That means the change is physical, not
chemical.
Chemical Changes
• Are different substances present after a change
takes place? If not, then the change is physical, not
chemical.
Chemical change:
 composition of the matter changes.
You got something NEW
Physical change:
 composition of the matter stays same.