Composition of
Matter
Composition of Matter
Substance (pure substance) –
• Matter that is either an element or a
compound
• A substance cannot be separated by
physical means.
Elements
• Substance in which all atoms are identical.
• Substance that cannot be separated into
simpler substances by physical or chemical
means
• There are 118 known elements.
Composition of Matter
• Atoms - The smallest unit of an
element that maintains the properties
of that element.
• Molecules – composed of two or
more elements that are joined by
chemical bonds. Smallest amount of a
compound that you can have.
Composition of Matter
• Compound - two or more elements
that are chemically combined.
Compounds
The ratio of the different atoms in a compound is
always the same.
Example:
H2O – 1 molecule of water has 2 H and 1 O
If you change the ratio, you no longer have water!
C6H12O6 - 1 molecule of glucose has
6 carbons, 12 hydrogens and 6 oxygens.
Compounds
Usually have a different appearance and properties
from the elements that make them up.
Elements
Compound
carbon
oxygen
C6H12O6
hydrogen
Elements and compounds
Cannot be reduced to more
basic components by physical
processes.
Mixtures
Material made up of 2 or more substances that can
be separated by physical means such as evaporation
or filtration.
Example – salt water, chocolate milk
Mixtures
Unlike compounds, mixtures do
not contain the same amounts of
the different substances that make
them up.
Mixtures - 2 Types
1. Homogeneous mixture – material in
which 2 or more substances are uniformly
spread out.
• Particles are so small that they cannot
be seen, even with a microscope.
• Also known as a solution
Solutions - Characteristics
• Never settle
• Remain constantly and uniformly
mixed
Examples – soda, vinegar, syrup
Mixtures
2. Heterogeneous mixtures – a mixture in which
different materials can be easily observed by the
naked eye or with a microscope.
• Will often settle if left to stand.
Examples – granite, chocolate milk, M&Ms
Suspension
• A heterogeneous mixture containing a liquid
in which visible particles settle.
• Made up of large particles that are too
heavy to stay suspended in a liquid
Examples – muddy water, glacial meltwater,
chicken soup, chocolate milk
Colloids
• A heterogeneous mixture that, like a
solution, never settles.
• Made up of medium sized particles
Colloid Examples
Colloid - How is it different than a
Solution?
A colloid scatters light – This is known as the
Tyndall effect. A beam of light will scatter when
pointed through a colloid.
Solution
Homogeneous
Colloid
Suspension
Heterogeneous Heterogeneous
Size of
particles
small
medium
large
Settle
upon
standing
No
No
Yes
Separate
with filter
paper
No
No
Yes
No
Yes
Yes
Scatter
light