Chemistry
Working scientifically
Scientific developments
economic
social
personal
environmental
Atomic Structure
Compounds
bonds
Mixtures
Chromotography
filtration
crystalisation
distillation
Atoms
Protons
Neutrons
Electrons
elements = atomic number
isotope - more neutrons
different atomic form of the same element
Na 23 - mass, 11 atomic number
Electronic structure
outer shell filled or removed
Periodic table
Atomic weight was incorrect way of sorting
helps see patterns in properties
Metals and non-metals
most elements are metal
most metals are transition metals
have different physical properties
Transition metals
can have more than one ion
often coloured
make good catalysts
copper, gold, palladium
Group 1 elements
alkali metals
easily broken
try to get rid of their electrons
Higher up the periodic table, the electrons are further away from the protons
lithium, potassium
Group 7 elements
react with non-metals (including oxygen)
halogens are all non-metals with colored vapors
they are all toxic
chorine, bromine, fluorine
as you go down group 7 the halogens are less reactive
higher melting points as they go up
Group 0 elements
nobel gases
don't have space to take electrons or give them away
helium, radon, argon
Bonding, Structure and Properties of Matter
Ions
Bondings
States of matter
made when electrons are transferred
are charged particles
if a metal and a non-metal react together, the metal looses electrons to become positively charged. The non-metal gains them to become negatively charged
Group 1, 2, 6 and 7 are the most likely to form ions
Group 1 and 2 are metals and they loose electrons to form positive ions (cations)
Group 6 and 7 are non metals, they gain electrons to form negative ions (anions)
Dot and cross diagrams
show how share electrons
ionic compounds
have a structure called a giant ionic lattice
all have similar properties
high melting points
high boiling points
when soild can't conduct electricity
when liquid - the ions are free to move to can conduct
Covalent bonding
means sharing electrons
when non-metal atoms bond together they share pairs of electrons to make these
Metalic bondings
polymers
lots of small units are linked together to form a long molecule that has repeating sections
all of the atoms in a polymer are joined by covalent bonds
giant covalent structures
high melting and boiling points
don't conduct electricity
Allotropes of carbon
all kept together by covalent bonds
are different structural forms of the same element in the same physical state
are no bonds in the layers, they are held together weakly
involves delocalised electrons
very conductive
alloys are harder than pure metals
Nanoparticles
large surface area to volume ratio
diameter between 2.5 x10(-6)m - 1x10(-5),
Quantitative Chemistry
Relative formula mass
percentage mass of an element in a compound = A(R) x number of atoms of the element / M(R) of the compound x 100
The mole and mass
The avogadro constant = 6.02x10(pr of 23)
The mole and equations
volume of gas = mass of gas / m(r) of gas x24
Solutions
concentration = number of moles in solute / volume of solute
Atom economy and percentage yield
atom economy = relative formula mass of desired product / relative formula mass of reactants x 100
percentage yield = mass of product actually made / maximum theoretical mass of product x 100
Chemical Changes
Acids and bases
PH goes from 0-14
Acids and bases neutralise each other
Titrations
allow you to find exactly how much acid is needed to neutralise a measure volume of alkaline
Acids
Acids can be strong or weak
Acid + metal carbonate -> salt + water + carbon dioxide
Metals and their reactivity
Acid + metal -> salt and hydrogen
Metal + water -> metal hydroxide + hydrogen
Redox reactions
Electrolysis
means splitting up with electricity
metals can be extracted from their ores using electrolysis
Electrolysis and aqueous solutions
Energy Changes
Exothermic and endothermic reactions
Bond energies
Cells
Fuel cells
factors affecting the rate of reaction
hydrogen-oxygen fuel cells involve a redox reaction
cathode produces heat for the equation and water
annode uses the hydrogen to fuel the reaction
temperature
concentration of a solution or the pressure of the gass
surface area
the presence of a catalyst
they decrease the activation energy
can be used multiple times
enzymes are biological catalysts
Reversible reactions
if you change one thing the reaction does that to the other side
Organic Chemistry
Uses and cracking of crude oil
Alkanes and their reactions
Fractional distillation
Addition polymers
Hydrocarbons
alkanes have all C-C single bonds
C(n)H(2n+2)
are homologous series
first four alkanes methane, ethane, propane and butane
long chain hydrocarbons are hard to crack
alkane bonds c=c
burn with a smokey flame
addition of hydrogen is known as hydrogenation
alkanes turn bromine water colourless
steam can react with alkanes to form alcohol
plastics are made up of long chain molecules called polymers
Alcohols
Have a 'OH' functional group and end in -ol
ethanal can be made by fermentation
Carboxylic acids
esters can be made from these
they have the functional group COO
condensation polymers
for each new bond that forms a small molecule is lost
naturally occurring polymers
amino acids have an amino group and a carboxyl group
proteins are polymers of amino acids
DNA molecules are made from nucleotide polymers
simple sugars can form polymers
Chemistry of the atmosphere
Chemical Analysis
Using resources
Materials and their properties
composites are generally made of two different materials
Alloys
Pure metals don't always have the properities needed
alloys are typically a mixture of two different metals
Corrosion
Iron and steel corrode much more than aluminum
Both air and water are needed for iron to rust
if a nail is put in with boiled water and oil on top - will not rust
Two main ways to prevent rusting
Painting / coating
Electroplating - uses electrolysis
The Haber process
produces ammonia from nitrogen and hyrdrogen
reacting gases are passed over a iron catalyst
at above 450 degrees Celsius and at high pressure
The more atmospheres the more yield