OCR Salters Chemistry, Chemistry For Life Notes

Used the spec and lesson notes- revision notes on developing fuels and elements for life. 

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Chemistry for Life
Elements of Life
Atomic number: number of protons in the nucleus.
Mass number: number of protons plus neutrons in the nucleus.
Isotope :Atoms of the same element which have different mass numbers.
Avogadro constant:One mole of any substance contains 6.02 x 1023 formula units.
Relative isotopic mass: Average of the masses of the isotopes taking into account their abundances.
Relative atomic mass (Ar): the mass of an elements atom relative to 12C=12.
Relative formula mass (Mr): the mass of a substances formula unit relative to 12C=12.
Relative molecular mass: sum of the relative atomic masses of the constituent atoms of a molecule.
Mass Charge
Proton 1 1
Neutron 1 0
Electron 0 -1
Atomic Emission Spectrum
1. Electrons get excited and move to a higher energy level
2. Electrons drop back to ground state by losing the amount of energy between the two energy
shells by emitting a photon of light.
3. The electromagnetic radiation emitted by an atom has a definite frequency related to the
difference in energy levels. E = hv
Lines get closer at a higher frequency
Atomic Absorption Spectrum
1. Electrons absorb light of the correct frequency to be excited up to a higher shell.
2. The electromagnetic radiation absorbed by each atom has a definite frequency related to the
difference in energy levels by E = hv
Similarities: both line spectra, lines in same position for a given element, lines become closer at
higher frequencies, sets of lines representing transitions to or from a particular level.
Differences: coloured lines on a black background or black lines on coloured background, the
relationship between the energy emitted or absorbed and the frequency of the line produced in
the spectra E = hv.

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Electron Structure
Element Atomic number 1st shell 2nd shell 3rd shell 4th shell
Hydrogen 1 1
Helium 2 2
Lithium 3 2 1
Berylium 4 2 2
Boron 5 2 3
Carbon 6 2 4
Nitrogen 7 2 5
Oxygen 8 2 6
Fluorine 9 2 7
Neon 10 2 8
Sodium 11 2 8 1
Magnesium 12 2 8 2
Aluminium 13 2 8 3
Silicon 14 2 8 4
Phosphorus 15 2 8 5
Sulfur 16 2 8 6
Chlorine 17 2 8…read more

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Unstable nuclei are radioactive.
Radiation What is it? Relative How does the Stopped by? Deflection in
charge nucleus change? electric field?
Alpha Helium nuclei +2 2 fewer protons Paper or skin Low
He 2 fewer neutrons
Beta Electrons -1 1 more proton Aluminium High
°e 1 fewer neutron foil
Gamma Electromagneti none No change Lead sheet None
c radiation
Half life: the time taken for half the radioactive nuclei in a sample to decay. It is fixed for any given
isotope.…read more

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Metallic lattice Metallic high insoluble Will conduct
Valence Shell Electron Repulsion Theory (around the central atom!)
6 groups of electrons ­ octahedral-90°
5 groups of electrons ­ trigonal bipyramidal-90°/120°
4 groups of electrons:
i. 4 bonding pairs ­ tetrahedral- 109°
ii. 3 bonding pairs and 1 lone pair ­
pyramidal- 109°
iii.…read more

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Mendeleev developed the Periodic Table by leaving gaps and rearranging some elements from their
atomic mass order. Subsequent research validated this knowledge.
Mass Spectrometer
Used to determine the mass of atoms or molecules.
Ionisation Chamber, acceleration area, drift region, ion detector.
a) Ionisation chamber: the atoms or molecules in the sample are bombarded with fast moving
electrons. His knocks and electron off each sample atom or molecule to form a 1+ ion.…read more

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Desorbed off surface. Important for the catalyst to
have a high surface area.
Homogenous catalysis: the catalyst and reactants are in the same physical state.
Catalyst poison: poison is strongly adsorbed onto the catalyst surface; the poison blocks the catalyst
surface, preventing reactants from bonding.
Cracking: a long alkane is broken into a shorter branched alkane and an alkene ­ zeolite is the
Reforming: alkanes are converted to cycloalkanes and hydrogen, cycloalkanes then are converted to
arenes and hydrogen ­ platinum is the catalyst.…read more

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Butane, Pentane, Hexane, Heptane, Octane, Nonane, Decane
Cycloalkanes: CnH2n, single bonds, aliphatic
Alkenes: CnH2n, unsaturated- double bond, aliphatic
Arenes: unsaturated, aromatic, simplest arene is C6H6 ­ benzene
Alcohols: have a hydroxylg group (OH), names end in OL, they react completely with oxygen to give
CO2 and water.
Ethers: have an alkoxy group (-OR) e.g OCH3 is methoxy and OC2H5 is ethoxy
Aliphatic: compounds that do not contain a benzene ring.
Aromatic: compounds that do contain a benzene ring.…read more

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Alkanes branched alkanes + branched alkenes
Alkanes smaller alkanes + cycloalkanes
Cycloalkanes alkenes + branched alkenes
Alkenes smaller alkenes
Anti knocking agents:
-Addition of additives (alkyl lead and oxygenates)
-interfere at different point in the pre-flame reactions
-oxygenates retard undesirable low temperature reaction
-alkyl lead compounds react in the intermediate temperature region to deactivate the major
undesirable chain branching sequence
Fuels containing oxygen in their molecules are called oxygenates. Blend with petrol- increase octane
number, cause less pollution.…read more

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Does not produce CO2, NOx, SO2. Risk of radioactive isotopes being released. Spent fuel rods highly
radioactive. Problems with decommissioning old nuclear power stations which use fission.
Renewable Sources:
Photovoltaic cells, windmills, hydroelectricity, solar thermal energy and wave/tidal barrages. No
harmful emissions. Unsightly. Problem of transporting the energy from where it is made to where it is
used. Currently unreliable.
Biodegradable. Living things absorb CO2 in the process. Less CO, CxHy, SO2 than a diesel engine. More
NOx emissions than a diesel engine.…read more


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