PDP Chemistry
Chemical reactions
Topic 1: Chemical reactions
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Atoms
Chemical reactions are atoms rearranging
Equations
Signs of a chemical reaction
Balancing chemical equations
Types of chemical reaction
Measuring chemical quantities
How are you going to take notes?
Atoms
What is everything made of?
In Six Easy Pieces, Richard Feynman said:
If, in some cataclysm, all of scientific knowledge were to be
destroyed, and only one sentence passed on to the next
generation of creatures, what statement would contain the
most information in the fewest words?
I believe it is the atomic hypothesis that all things are made of
atoms.
(Almost) everything is made of atoms
Images:http://en.wikipedia.org/wiki/Rock_(geology),
http://en.wikipedia.org/wiki/Tree ,
http://en.wikipedia.org/wiki/Human, http://en.wikipedia.org/wiki/Star
How big is an atom? about 10-10m
 if an atom was the size of a grain of sand, humans would be
the size of a planet.
Image: http://en.wikipedia.org/wiki/Earth, http://en.wikipedia.org/wiki/Sand
The periodic table lists the elements in
order of atomic number
Image: http://en.wikipedia.org/wiki/File:Periodic_table.svg
Chemistry is atoms
rearranging
Describing chemical changes
Liquid oxygen and
liquid hydrogen fuel
Launch of Apollo 11
(from 6 min)
Image: http://en.wikipedia.org/wiki/Saturn_V
Some changes are only changes of phase,
not chemical changes
Image:
https://commons.wikimedia.org/wiki/Categor
y:States_of_aggregation
Atoms are rearranged to make new
substances in chemical reactions.
Hydrogen + Oxygen  Water
2 H2 + O2  2 H2O
Image: http://labspace.open.ac.uk/mod/resource/view.php?id=438900
Equations describe
chemical reactions
reactants  products
Hydrogen + Oxygen  Water
2 H2 + O2  2 H2O
State symbols
(s)
(l)
(g)
(aq)
Signs of a chemical change
How do we know a chemical reaction is occurring?
Sodium reacts with water
Dilute sulphuric acid reacts with
potassium hydroxide solution
Lead nitrate solution reacts with
potassium iodide solution
Magnesium and hydrochloric acid
Signs of a chemical change
Elements, compounds,
atoms, molecules, ions
Molecules
 Build a molecule PhET
http://phet.colorado.edu/en/simulation/build-a-molecule
 States of matter: Basics
http://phet.colorado.edu/en/simulation/states-of-matterbasics
What is an atom?
Symbols and formulae
Ethane, C2H6
Naming compounds
Ionic compounds (usually metal + non-metal)
 NaCl
 KI
 LiF
 CaCl2
 MgSO4
 CaCO3
 H2SO4
 H2O
Common Cations
Common Name Formula Alternative
name
Simple Cations
Aluminium
Al3+
Calcium
Ca2+
Copper(II)
Cu2+
cupric
Hydrogen
H+
Iron(II)
Fe2+
ferrous
Iron(III)
Fe3+
ferric
Magnesium
Mg2+
Mercury(II)
Hg2+
mercuric
Potassium
K+
kalic
Silver
Ag+
Sodium
Na+
natric
Polyatomic Cations
Ammonium
NH4+
Hydronium
H3O+
Common Anions
Common Name Formula
Simple Anions
Chloride
Cl−
Fluoride
F−
Bromide
Br−
Oxide
O2−
Polyatomic anions
Carbonate
CO32Hydrogen
HCO3−
carbonate
Hydroxide
OH−
Nitrate
NO32Phosphate
PO43Sulfate
SO42Anions from Organic Acids
Ethanoate
CH3COO−
Methanoate
HCOO−
Ethandioate
C2O4−2
Cyanide
CN-
Alternative
name
bicarbonate
acetate
formate
oxalate
Covalent compounds (usually non-metals)
 CO2
 H2O
 CO
 NH3
 SO2
 SO3
 CH4
Equations for lab
Balancing chemical
equations
Balanced equations show the mole ratio
of reactants and products
Hydrogen + Oxygen  Water
2 H2 + O2  2 H2O
Image: http://labspace.open.ac.uk/mod/resource/view.php?id=438900
2 H2 + O2  2 H2O
green numbers = subscripts
cannot be changed (a compound has one formulachanging the formula changes the compound)
red numbers = coefficients
changes to balance the reaction (coefficients valid only
for a specific reaction)
Balancing a chemical equation
Propane + oxygen  carbon dioxide + water
_ C3H8(g) + _ O2(g)  _ CO2(g) + _ H2O(l)
C3H8(g) + 5 O2(g)  3 CO2(g) + 4 H2O(l)
What does an equation tell us about molecules in the reaction?
 you need 5 oxygen molecules for 1 molecule of propane
 1 propane molecule will produce 3 carbon dioxide molecules
and 4 Water molecules
 2 molecules of propane produce 6 molecules of carbon
dioxide
 1 mole of propane produces 3 moles of carbon dioxide
Measuring chemical quantities
Measuring chemical quantities: solids
 in grams
 using a balance (precision ±0.01g or ±0.001g)
Image: http://en.wikipedia.org/wiki/Weighing_scale
Measuring chemical quantities: liquids
 in litres (L) or decimetres cubed (dm3)
1L = 1dm3
 In mL or centimetres cubed (cm3)
1mL = 1cm3
 1000 mL = 1L
Images: http://commons.wikimedia.org/wiki/Category:Laboratory_glassware
Converting mass to volume
 volume = mass x density
 volume of pure water is 1.0 gcm-3
Solutions
 a solute dissolved in a solvent gives a solution
 units of concentration grams per litre (gL-1)
 or moles per decimetre cubed (moldm-3, M)
Types of chemical reaction
 -synthesis
 -decomposition
 -displacement
 -double displacement (special type acid-base)
 -combustion
Links
 Powers of ten http://www.powersof10.com/
 hydrogen explosion
http://www.youtube.com/watch?v=DjcztiNGg_8
 states of matter phet
http://phet.colorado.edu/en/simulation/states-of-matter