Physical and Chemical Changes
Chem 8
Physical Properties
Any characteristic of a material that you can
observe without changing the substances
that make up the material
• EX: shape, size, texture, phase of
matter, density, BP, MP
Physical Change
change in the size, shape, or state of matter
EX: melting iron, water
freezing, crumpling
paper, smashing a rock
Chemical Properties
A characteristic of a substance that indicates
whether it can undergo a certain chemical
change
• EX: Flammability, radioactivity,
new substances can be formed
Chemical Change
A change of one substance in a material to a
different substance
• EX: foaming of antacid tablet
• What in the picture is chemically
changing?
Chemical Reactions
• When a chemical reaction occurs,
there is always a change in the
properties and energy content of the
substances involved. There is a
change in both the physical and
chemical properties as substances are
changed into new substances. Most of
the time, at least one of the following
will be obvious when a chemical
reaction takes place:
6 indications of a chemical change
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•
•
•
•
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1. Color change
2. precipitate - cloudy
3. formation on light
4. heat given off
5. gas given off – bubbles/ fizzes
6. new substance with new properties
Phase Change
The physical change of matter from one phase to another.
A phase change takes place because the particles of a substance
gain or lose energy, causing them to change their motion
Names for phase changes
– Melting - Solid changes to Liquid
– Freezing - Liquid changes to Solid
– Sublimation - Solid changes to Gas
– Snow - Gas changes to Solid
– Vaporization - Liquid changes to Gas
• Evaporation - vaporization that takes
place at the surface of a liquid.
– Condensation - Gas to Liquid
Draw the following graph into your notes:
Boiling Point Temperature
The temperature at which a liquid boils
• Water boils at 100 oC, 212 oF
• Table salt boils at 1413 oC
• Diamond boils at 4200 oC
Freezing Point Temperature
The temperature at
which a liquid
changes to a solid
• Water freezes at
0 oC, 32 oF
• Table salt freezes
at 801 oC
• Diamond freezes
at 3700 oC
Melting Point Temperature
The temperature at which a solid changes to a
liquid
• Water (ice) melts at 0 oC, 32 oF
• Table salt melts at 801 oC
• Diamond melts at 3700 oC
LAW OF CONSERVATION OF MATTER & ENERGY
States that Mass cannot be
created or destroyed only
conserved
IT ONLY CHANGES FORMS
Law of Conservation of Mass