C1 Revision
Atomic structure
• Atoms consist of a central nucleus which contains protons and neutrons
• The nucleus is surrounded by shells of electrons
Electron Structure
• The atomic number of an element gives the number of electrons
• The max number of electrons in each shell is 2,8,8
Electrons and the periodic table
• Groups = the columns (up and down) the table
• Periods = the rows (going across) the table
• Number of electrons in outer shell = group number
• Number of shells = period number
Mendeleev
• Developed the modern Periodic table
• Arranged the elements in order of their atomic mass
• Left gaps for undiscovered elements
• Predicted properties for elements in gaps
• When discovered, properties of the new elements matched the predictions
Group 1 reactions
• Group 1 – lithium, sodium, potassium• Group 1 react with oxygen to form oxides• Eg. Lithium + oxygen Lithium oxide
• Group 1 react with water to form hydroxides and hydrogen gas
• Eg. Sodium + water Sodium hydroxide + hydrogen
• Reactivity of group 1 increases going down the group
Group 7 displacement reactions
• Group 7 reactivity decreases down the group
• A more reactive halogen can displace a less reactive halogen from a compound
• Chlorine + sodium bromide Bromine + Sodium chloride
Flame tests and silver nitrate tests
• Flame tests can be used to identify sodium or potassium in a compound
• Sodium – orange yellow flame• Potassium – lilac flame
• Silver nitrate can be used to identify chloride or iodide in a compound
• Chloride – white precipitate• Iodide – yellow precipitate
Chemical formulae
• Each element in a formula has a capital letter
• The number of atoms is written after the symbol
Combining ions
• To work out a formula from the table of ions,
• Write down the positive and negative ions
• “Swap and drop” the numbers
• eg. Al3+ and Cl- becomes AlCl3
Acid reactions
• Acids react with metals to form a salt and hydrogen
• Eg. Magnesium reacts with sulphuric acid to form magnesium sulphate (salt) and hydrogen
Acid reactions
• Acids react with metal oxides to form salt and water
• Eg. Copper oxide reacts with sulphuric acid to form copper sulphate (salt) and water
Acid reactions
• An alkali is a metal hydroxide
• Acids react with alkalis to form a salt and water
• eg. Sodium hydroxide reacts with hydrochloric acid to form sodium chloride (salt) and water
Acid reactions
• Acids react with metal carbonates to form a salt, carbon dioxide and water
• Eg. Calcium carbonate reacts with sulphuric acid to make calcium sulphate, carbon dioxide and water
Signs of a chemical change
• Colour change
• Precipitate
• Temperature change
• Produces a gas
Exothermic and Endothermic
• An exothermic reaction is a reaction which gives out heat
• An endothermic reaction is a reaction which takes in heat
Rates of reaction
• Factors which affect rate of reaction are:– Temperature (higher temperature increases
rate)– Concentration (more concentrated acids
react faster)– Surface area (crushing up solid into a powder
makes it react faster)– Adding a catalyst (a substance added to the
reaction to make it faster)
Nanoscience
• A nanometre is 1 thousand millionth of a metre • A nanoparticle is a particle that has a size in
the range 1 to 100nm• Nanoparticles have new and different
properties to the same material in bulk form• Eg. Nanosilver which is antibacterial and is
used in sterilising sprays in hospitals and self cleaning fridges
• Some people concerned – may pass through the skin as so small. Long term effects on health not known.
Crude oil
• Mixture of hydrocarbons
• Hydrocarbon = compound of carbon and hydrogen only
• Each fraction in crude oil has a different boiling point
• Larger molecules – higher the boiling point
• Separated by fractional distillation
Fractional distillation
• Crude oil is heated and enters fractionating column
• Vapours cool down as they rise up the column
• High boiling point fractions (large molecules) condense at the bottom of the column
• Low boiling point fractions (small molecules) condense at the top of the column
Fuels
• Hydrocarbons can be burned to produce energy (react with oxygen) - combustion
• Products are carbon dioxide and water
• Carbon dioxide contributes to global warming – greenhouse gas
• Some fuels contain sulphur as an impurity
• Sulphur burns to make sulphur dioxide which contributes to acid rain
Atmosphere
• Early atmosphere came from volcanoes• Atmosphere has changed over geological time (millions
of years)• Evolution of life has had a massive impact on the
atmosphere• Plants – photosynthesis – use up carbon dioxide and
make oxygen• All living things – respiration – use up oxygen and
produce carbon dioxide• Combustion of fuels – uses up oxygen and produces
carbon dioxide• All three processes keep the levels of oxygen and
carbon dioxide the same
Global warming
• Increase in CO2 due to burning hydrocarbon fuels
• Earth radiates heat which is then trapped by the atmosphere, the more CO2 there is the more heat is trapped
• Greenhouse effect
Continental drift
• Alfred Wegener – theory of continental drift
• Continents were once joined and have split up and moved apart
• Evidence – closely fitting coastlines, matching fossils and rocks in different continents
• Why not accepted in Wegener’s time? He couldn’t explain how continents move
Plate tectonics
• Explains Wegeners theory• Earth’s crust is broken up into pieces called
tectonic plates• Plates are moving – this is how continents have
moved apart• Some plates move apart – magma rises to fill
the gap forming new igneous rock• Plates move together, one plate sinks beneath
the other and melts to form magma• Earthquakes and volcanoes occur on plate
boundaries