Transcript year 9 chemistry revision

YEAR 9 CHEMISTRY
REVISION
GOOD LUCK!
Structure of Atom
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In the cloud : Electrons (negative)
In the Nucleus: Protons (positive)
Neutrons (neutral)
Subatomic Particles
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In an atom: The Protons = the Electrons
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If 20 protons are present in an atom then 20
electrons are there to balance the overall
charge of the atom—atoms are neutral
The neutrons have no charge; therefore
they do not have to equal the number of
protons or electrons
Atomic Number
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Atomic number: this number indicates
the number of protons (and electrons)
in an atom
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Ex: Hydrogen’s atomic number is 1
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So hydrogen has 1 proton and 1 electron
Ex: Carbon’s atomic number is 6
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So carbon has 6 protons and 6 electrons
Physical Change
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A changes in certain properties such as:
Shape
State (Solid, liquid, gas)
NO NEW SUBSTANCES ARE CREATED
Examples: dissolving sugar, melting ice
Chemical Change
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Chemical changes produce new
substances
Heat
Gas
Bubbles
Light
Examples: making toast, burning wood
Metals
React with acids
They are more of them than non-metals and are on
the left side
Conducts electricity
Glows quickly and cools quickly
Generally sink
Shiny and strong
Non Metals
On the right side of the periodic table
Generally float
Gases at room temperature
Don't conduct electricity and so they are
insulators
Really slow to heat up or cool down
Very brittle- which means they break easily
Very dull looking
Acids
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pH 1-6
React with Metals
turn blue litmus paper red
corrosive
sour taste
red/pink in universal indicator
Common examples: Milk, HCL, Citric Acid
Bases
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pH 8-9
Turns red litmus paper blue
bitter
blue/ purple in universal indicator
common examples: soap, detergent,
cleaning products
Neutrals
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pH 7
No reaction to litmus paper
Green in universal indicator
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ACID + BASE = Neutralisation
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Common Examples: Water
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Acid and Metal Reactions
1. Acid + Metal -> Salt + Hydrogen Gas
Acid + Metal Carbonate -> Salt + water + Carbon
Dioxide
Acid + Base -> Salt + Water