Chapter 17
Section 1—Composition of Matter
Section 1
• Pure Substances– Either an element or a compound that
cannot be broken down into simpler
components and still maintain the
properties of the original substance
ex: helium, aluminum, water, salt
Elementsa substance whose atoms are all alike
*there are 90 found in nature/20
others made in labs
• Compounds
– A substance in which the atoms of two
or more elements are combined in a
fixed proportion
• Ex: water, chalk, etc.
• Compounds usually look different from the
elements in them (salt—Na and Cl)
• Mixtures– A material made up of two or more
substances that can be easily
separated by physical means
– Heterogeneous Mixtures:
• A mixture in which different materials can
be distinguished easily
• Ex: granite, concrete, pizza
• Homogeneous Mixtures:
• Contains two or more gaseous, liquid or
solid substances blended evenly
throughout
• Ex: soft drinks, vinegar, etc
• Solution• A homogeneous mixture of
particles so small that they cannot
be seen with a microscope and will
never settle to the bottom of their
container
– Ex:
– Colloid:
– A type of mixture that never settles
– It’s particles are larger than those in
solutions but not heavy enough to
settle
– Ex: some paints, shampoos, hairgel,
• Tyndall Effect:
• The scattering of light by colloidal
particles
• A light beam is invisible as it passes
through a solution, but can be seen
readily as it passes through a
colloid
– Ex: pg. 523
• Suspensions:
• A heterogeneous mixture
containing a liquid in which visible
particles settle
– ex: muddy pond water (visible
particles settle out eventually)
SECTION 2—Properties of Matter
• Physical Properties• Any characteristic of a material
that can be observed without
changing the identity of the
substance
– Ex: color, shape, size, melting/boiling
pt, etc.
Physical Properties may be used to
separate substances (in a mixture)
• Physical change
a change in size, shape or state of
matter
(might involve energy changes but
element or compound itself does
not change)
*PHYSICAL CHANGES ARE PHASE
CHANGES!!
Distillationprocess for separating substances
in a mixture by evaporating a liquid
and recondensing its vapor
• Chemical properties
– A characteristic of a substance that
indicates whether it can undergo a
certain chemical change
– Ex: flammability, exposure to light
Chemical Change:
A change of one substance to another
Ex: foaming of antacid tablets, silver
tarnishing, etc.
*A NEW SUBSTANCE IS
FORMED BY A CHEMICAL
CHANGE!!!!
Weathering—Chemical or Physical?
• Some weathering changes are
physical and some are chemical
• Physical—rocks split, streams cut
through rock, etc.
• Chemical—calcium carbonate from
limestone changes to calcium
hydrogen carbonate
– Ex: White Cliffs of Dover
The Conservation of Mass
• Law of Conservation of Mass
Matter is neither created nor
destroyed (during a chemical
change)
The mass of all substances that are
present before a chemical change
EQUALS the mass of all the
substances that remain after the
change