Download The science of chemistry

THE SCIENCE OF
CHEMISTRY
1.1 What is Chemistry?
1. Are there “good” chemicals and
“bad” chemicals?
2. Are there any chemicals that you can
never have too much of?
What is matter?
• Matter is anything that has
volume and mass
What is a chemical?
• Any substance with a definite
composition – can be a single
atom or a large molecule
Physical properties
Examples:
Mass
Density
Color
Physical properties can
be measured or seen
through direct observations.
PHYSICAL CHANGES
 Words
such as boil, freeze, melt, and condense are
used to describe physical changes.
 So
are words such as break, split, grind, cut, and
crush.
 There
is a difference between these two sets of
words. Each set describes a different type of
physical change.
PHYSICAL CHANGES
Physical
changes can be classified as reversible or
irreversible.

Melting is an example of a reversible physical
change.
PHYSICAL CHANGES
All
physical changes that involve a change
from one state to another are reversible.
 Cutting
hair, filing nails, and cracking an
egg are examples of irreversible physical
changes.
Chemical properties
are observed when
a substance changes into
a different substance.
Iron
Chemical change
Rust
The Law of Conservation of Matter
Matter can neither be created nor destroyed….WHAT GOES
IN MUST COME OUT!!!
a. The Evolution of a Gas The production of a gas is often observed by
bubbling, or by a change in odor.
b. The Formation of a Precipitate When two clear solutions are mixed and
become cloudy, a precipitate has formed, as shown in.
c. The Release or Absorption of Energy A change in temperature or the
giving off of light energy are signs of an energy
transfer.
d. A Color Change in the Reaction System Look for a different color
Signs that a chemical change has occurred