Transcript Composition of Matter

Composition of Matter
Chapter 17 section 1
Substances
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A substance is something that can not be
broken down and still maintain its original
characteristics/properties
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Elements are examples of a substance
Compounds are examples of a substance
Difference Between Element and
Compound
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Element-Combination of like atoms
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Entire substance is made of the same type of
atom
Example-aluminum foil
Compound-A substance in which two or
more atoms are combined in a fixed
proportion to become stable
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Example-H2O
Mixtures
 A material made up of 2 or more
substances
 Mixtures do not always combine the same
proportions
 Example-Saltwater
 Mixtures can be separated
 Example/Question-What happens when you boil
salt water
 As the water evaporates the salt is left behind
Types of Mixtures
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There are 3 different types of mixtures
1. Homogenous mixture-contains 2 or more
gaseous, liquid, or solid substances that are
evenly blended
– Examples
– Coffee with milk and sugar (that has been dissolved)
– Shows diffusion of molecules
– Sugar and salt mixture that is mixed up evenly
– Homogenous mixtures create a solution
– Solution-particles so small that they cant be seen without
the use of tools (microscope)
Types of Mixtures (continued)
2. Heterogeneous mixture-A mixture in which
materials are not evenly blended
–
Sometimes they can be easily separated (not always)
– Example-a pizza is made up of crust, sauce,
cheese and pepperoni
– Certain types of cereal-Raisin bran or Lucky
charms
– Some heterogeneous mixtures will separate over
time
– Heterogeneous mixtures that will settle = suspension
– Example-River carrying dirt or sand
Types of Mixtures (continued)
3. Colloids-contains particles in varying
proportions (heterogeneous) but particles will
not settle over time
– Examples–Fog (water particles suspended in air),
hair gel, and some shampoos
– Test for colloids using the Tyndall effect
– Tyndall effect is the scattering of light as it passes through
a colloid
– You can see the beam because the particles in the
mixture are big enough to cause the light to scatter