2.1 Definitions
Pure
substance
Solution
Element
Atom
suspension
colloid
Qualitative
Quantitative Miscible
Compound
Heterogeneous
mixture
Homogeneous
mixture
Immiscible
Matter - anything that has mass is made up of matter.
Pure Substance - A sample of matter (stuff) that consists of only one component material
with physical and chemical properties that are the same with all matching materials.
Examples: water, wood, sand, sugar salt.
Atom- the smallest particle of an element. Matter is composed of atoms in various
combinations.
Atoms can be considered the building block of all matter.
From: http://education.jlab.org/qa/history_01.html
Around 2,500 years ago this Greek philosopher named Democritus was sitting around just
thinking. He was thinking about cutting stuff up and came up with the idea that there must be a
point where you could no longer cut something any smaller. He named the atom after the
Greek word atomos, which means that which can't be split. The cool part is that he was right,
well 90% right.
We can split atoms, but if you split an atom it becomes something else. An atom is the
smallest unit of a particular kind of material. For example if you cut a gold block into smaller
and smaller pieces you would eventually be left with one gold atom. If you cut that atom into
pieces you don't get smaller pieces of gold, you get protons, neutrons and electrons, which can
be rearranged into something completely different.
Democritis was mostly correct and well ahead of his time.
What does an atom look like?
This is an image of silicon
atoms arranged on a face of
a crystal. It is impossible to
"see" atoms this way using
ordinary light. The image
was made by a Scanning
Tunneling Microscope, a
device that "feels" the cloud
of electrons that form the
outer surface of atoms,
rather as a phonograph
needle feels the grooves in a
record.
It had long been suspected that crystals are made of atoms lined up in neat arrays. But
at the start of the 20th century there was no way to actually see them. Some scientists
thought the "atom" in physics theories might be merely a sort of abstract device useful
for computations. Einstein's paper gave one of the first convincing proofs that atoms
do exist as real objects.
From: http://www.aip.org/history/einstein/atoms.htm
Element- a substance whose atoms are all the same.
This means they react the same. They look the same.
There are about 100 known elements. They are all listed in the Periodic Table of Elements.
Example: Atoms of gold are the same as all atoms of gold. However, atoms of gold are
different than atoms of silver or lead. Gold, silver and lead are all elements.
Symbols for the Elements:
3
Li
6.941
The names were originally from Latin which is why some of them do not seem
to make sense.
For this unit you should k now the first 20 elements. Identify the ones that do
not seem to match their names.
Compound- a composition of various elements.
Example: Water is a compound made up of 2 atoms of the element Hydrogen and 1 atom of the
element Oxygen atom.
Types of Mixtures:
Heterogeneous mixture– a mixture which is not the same throughout.
 Chocolate chip cookies are heterogeneous because you can take
two samples at different places and they may not be the same,
one sample may not include a chip.
 Ice cream with raisins
 Brownies with nuts.
Homogeneous mixture– a mixture which is the same throughout. A sample taken at any
place will be the same.
Examples: Vanilla ice cream, plain bread.
Types of mixtures including a liquid:
Solutions – the homogeneous mixture of a liquid and dissolved solid or two liquids.
Examples:
 sugar and water – most drinks are mostly sugar dissolved in water
 alcohol in water – alcoholic drinks are mostly water with sugar and alcohol dissolved
 gasoline and Styrofoam – will mix to create a homogeneous liquid
Suspensions – this type of heterogeneous mixture will separate into its components unless
continually stirred or shaken. The components don’t like to mix and separate.
Examples:
 Sand and water
 Water and oil.
Here you see Liquids which have separated on the left and liquids that do not separate on the right.
From: http://chemistry.tutorvista.com/physical-chemistry/dilute-solution.html
Miscible – two liquids that will mix and stay mixed.
Immiscible – two liquids that will not mix but will separate if left alone.
Colloids - a homogeneous substance consisting of large molecules or ultramicroscopic particles of one
substance dispersed through a second substance. Colloids include gels and emulsions; the particles do not settle
and cannot be separated easily.
Types of observations:
Quantitative – assigning a numerical value to describe an observation
Qualitative – describing an observation with a description
Example: Length of a trip:
Quantitative: 150 miles
Qualitative: Longer than from here to New York City.
Qualitative only: Scent, Taste,
When measuring scents or tastes it is very difficult to assign a number. These measurements are almost strictly
qualitative.
People that do this for a living might taste test ice cream, wine, beer, or any food type item.
Testing Wine
Testing Beer
Can you tell the difference between the tea?
Smell Testing for Deodorant.