Year 9 Science
Mrs Dover
 There
are over 100 known elements that
make up all matter
 These elements are arranged in a Periodic
Table so that similar elements are in the
same column (group)
 Scientists can refer to individual elements
by their characteristic symbols. For
example:
 Carbon C
 Hydrogen
H
 Oxygen
O
MATTER: The elements
The Elements song by Tom Lehrer
http://www.youtube.com/watch?v=DYW50F42ss8
Mrs Dover
9 Science
Scientists classify changes in materials as
either A physical change (eg. water boiling
and turning into steam)
 A chemical reaction (eg. iron
rusting)
 A nuclear reaction (eg. the formation
of helium from hydrogen on the sun)
A combination of the following observations:
A
new substance is formed
 Bubbles
(gas is produced)
 Change
in temperature- warmer or
colder (without the substances being
heated or cooled)
 Change
A
in colour
precipitate (solid) forms
It destroyed the
Hindenburg
airship on May 6,
1937
Meet O2
You need me.
I’m important.
Meet H2
B-b-b-b-b
He’s light.
He’s fast.
He’s crazy!
One day…
Hey!
Quit it!
Chemical Reactions
Bonds are broken and
new bonds are formed.
Bonds in H2 & O2 break.
Chemical Reactions
Bonds are broken and
new bonds are formed.
New bonds form.
Chemical Reactions
New substances
are formed.
2 gases react
Water is formed
Parts of a Reaction
Reactants:
The chemicals you have before the reaction
That’d be us.
Tbtbbhth!
Tbtbbhth!
H2
O2
H2
Parts of a Reaction
Products:
The substances formed in the reaction
H2 O
H2 O
Chemical Equation
Reactants
Products
Chemical Reactions
During chemical reactions atoms are not
created or destroyed. They’re just rearranged.
2 oxygen atoms
4 hydrogen atoms
2 oxygen atoms
4 hydrogen atoms
 Solid
copper carbonate decomposes to
form carbon dioxide and copper oxide.
copper carbonate  carbon dioxide + copper oxide
 Sodium
hydroxide is used to neutralise
some hydrochloric acid. Harmless water
and sodium chloride is produced.
sodium hydroxide + hydrochloric acid  water + sodium chloride

When lead nitrate is mixed with potassium chloride,
a yellow precipitate (lead chloride) forms in a
solution of potassium nitrate.
lead nitrate + potassium chloride  lead chloride + potassium nitrate

A piece of magnesium ribbon is placed in some
copper sulfate solution. As the magnesium
dissolves, the solution loses its blue colour showing
that magnesium sulfate is forming. A brown
coloured solid appears at the bottom of the test
tube. This is copper metal.
magnesium + copper sulfate  magnesium sulfate + copper
 Exothermic
reactions produce energy as
heat. The test tube will feel warm / hot.
 Endothermic reactions absorb heat
energy from the surroundings. The test tube
will feel cold.
http://www.jce.divched.org/JCESoft/CCA/pirelli/p
ages/cca3glycerin.html video
http://www.youtube.com/profile?user=robertburkottawa#p/u/3/5RJLvQXc
e4A video
 Rules:
reactants
products
Types of
elements
Types of
elements
Numbers of
each type of
element
Numbers of
each type of
element
1. Write the equation using the
provided chemical formulas
for each reactant and product.
2. Check that the same
elements are shown on both
the reactants side and the
products side of the equation.
3. Balance the equation by only
placing coefficients
(numbers) IN FRONT OF a
reactant or product formula.
 At
year 9 level, you will always be given
the correct formulas for the reactants and
products.
 Precipitation
reaction
http://www.jce.divched.org/JCESoft/CCA/pirelli/pages/cca1NaIHgCl2.html
http://www.jce.divched.org/JCESoft/CCA/pirelli/pages/cca4CdNO3Na2S.html