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Elementary,
My Dear Watson
Exam Review 2013
Matter
All matter is made up of tiny particles called
atoms.
These atoms are made up of even smaller
particles:
electrons (which have a negative charge)
protons (which have a positive charge)
neutrons (which have not charge)
Electron
Neutron
Proton
in the
nucleus
The Periodic Table
The rows are called periods and they are
arranged by atomic number. We use
numbers to identify them.
The columns are called families. Each
column contains elements that have
similar properties.
The elements are metals, non-metals or
metalloids (having both properties of
metals and non-metals).
Each square in the Periodic Table tells us
something about the element.
The atomic number is equal to the
number of protons.
atomic number
1
H
Hydrogen
chemical symbol
element’s name
If the chemical symbol is made up of one
letter, it is always a capital. For example:
H is hydrogen
C is carbon
If the chemical symbol is made up of two
letters, the first is a capital letter and the
second is a minuscule (small) letter. For
example:
Cl is chlorine
He is helium
How Many?
The number of protons = atomic number
Protons are found in the nucleus
The number under the chemical symbol is
the atomic mass (the mass of one atom of
that element)
4 9.012182
atomic
number
Be
Berylium
atomic mass
chemical symbol
element’s name
To find the number of neutrons, you need
to round the atomic mass to the nearest
whole number.
Then subtract the number of protons
from the atomic number and you will get the
number of neutrons found in the nucleus of
the atom, intermingled with the protons.
4 9.012182
Be
Berylium
Step 1. Round atomic mass: 9 amu
Step 2: 9 - 4
Step 3: 5 neutrons
Mysterious Molecules
When two or more atoms join together,
they form molecules.
A molecule could be made up of atoms of
the same kind. For example: O2 (oxygen)
and 03 (ozone).
A molecule could also be made up of
different atoms. We often call these
compounds. Here are some
examples: CO2,
H20,
C6H1206
The letters represent the elements that
are involved and the numbers tell us how
many atoms of each kind are involved.
For example, water (H20) is made up of
2 atoms of hydrogen and 1 atom of oxygen.
For example, carbon dioxide (CO2) is
made up of 1 atom of carbon and two
atoms of oxygen.
Whereas sulphur dioxide (SO2) is made up of 1
atom of sulphur and 2 atoms of oxygen.
We can draw molecules using Dalton’s
model. For example, if
= Carbon
= Oxygen
then we can draw CO2 as
and we can draw H2O as
= Hydrogen
Physical Changes
No new substances are being formed.
The product has the same chemical
formula as the reactants.
A physical change could involving
separating a mixture into its components.
Physical Changes
Physical changes involve a change in the
physical properties of the substances: state
of matter, shape, temperature, particles.
Physical changes are often (but not
necessarily) reversible.
Chemical Changes
In a chemical change, a new substance is
made.
The product has a different chemical
formula from the reactants.
A chemical change is usually accompanied
by one of the following signs:
Colour
Change
Light
Effervescence
(Bubbles)
Precipitate
Temperature
Change
Conservation of Matter
Lavoisier’s law states that the mass of
the reactors equals the mass of the
products
Examples:
a) CH4 + 2 O2 ---> CO2 + 2 H2O
5 g + 8 g ----> 7 g + ?
b) C3H8 + 5O2 ---> 3 CO2 + 4 H2O
10g + 4 g ---> ?
+ 9g
Answer: 6 g
Answer: 5 g
Conservation of Matter
Remember the vinegar and baking soda
lab we did:
the mass of the reactors (baking soda and
vinegar) was equal to the mass of the
product (fizz!) only when we placed a
balloon on top of the Erlenmeyer Flask to
catch the gas (CO2) that was produced.
Otherwise, the mass after the reaction
would have decreased because the
produced CO2 could have escaped.
Electrolysis
Water can be decomposed into its
original elements using electrolysis.
When water is split apart, there is twice
as much hydrogen as there is oxygen,
since the molecular formula for water is
H2O.
For example:
if we get 20 ml of hydrogen
we should get 10 ml of oxygen
Electrolysis
When you test the gases after
decomposing water, they produce the
following results:
oxygen bursts in flame (glowing splint test)
hydrogen makes a small pop (flaming splint
test)