126.96.36.199 Neutron--------------------1------------------ no charge
188.8.131.52 electron--1/1840(or almost nothing so usually ignored-- 1-(negative)
2.1.2 Because they make up the atom, protons,
neutrons and electrons are called subatomic
2.1.3 Nucleon number
184.108.40.206 Proton and neutron form the nucleus and so are called
nucleons. Nucleon number is total number of protons and
neutrons. Nucleon number= mass number
2.1.4 Proton number
220.127.116.11 Number of electrons= number of protons= proton number
18.104.22.168 Elements in the Periodic table are in
order of their periodic number
22.214.171.124 Isotopes are atoms with the same proton
number but different nucleon number.
126.96.36.199 Radio isotopes are
unstable atoms, which
break down giving
188.8.131.52.1 cancer treatment (radiotherapy) –rays kill
cancer cells using cobalt-60.
184.108.40.206.2 to check for leaks – radioisotopes called tracers are added to oil
or gas. At the leaks radiation is detected using a Geiger counter
2.2 Bonding: the structure of matter
2.2.1 Element contains only one type of atom, compound
contains more than one type of atom, held together by
chemical bonds and mixture can contain any different
number of different substances which are not
chemically bonded but are just mixed
2.2.2 Alloy: a mixture where at least one other substance is
added to a metal, to improve its properties
220.127.116.11 brass (70% copper and 30% zinc) is harder than copper,
does not corrode, used in musical instruments.
18.104.22.168 Stainless steel (70% iron, 20% chromium and 10% nickel) unlike iron does
not corrode, used in car part and cutlery
2.2.3 Ionic Bonding
22.214.171.124 An ionic compound (in solid state) has a regular
arrangement (lattice) of alternating positive and
126.96.36.199 The bond formed between ions of opposite charge. Also between
metal and non-metal
2.2.4 Covalent Bonding and macromolecules
188.8.131.52 A covalent bond forms between two atoms and is the attraction of
two atoms to a shared pair of electrons. Small groups of covalent
bonded atoms can join together to form molecules
184.108.40.206 Silicon (IV) oxide (SiO2 ) has a structure with each
Si joined to 4 O and each O joined to 2 Si. It is the
main ingredient in glass. It is also sand
220.127.116.11 Silicon (used in microchips for computers) has the
same structure as a diamond
18.104.22.168 Diamond: The covalent bonds are very strong.
Diamond is the hardest naturally occurring
material. It does not conduct electricity.
22.214.171.124 Graphite: Each layer is itself a giant molecule with very strong covalent bonds.
Between the layers is delocalised (it is a free electron). Between the layers the bonds
are weak. Free electrons between the layers allows graphite to conduct electricity and
heat. The layers can easily slide over each other making graphite soft and slippery
and an excellent lubricant (like oil)
2.2.5 Metallic Bonding
126.96.36.199 lattice of tightly packed positive ions in a sea of electrons,
resulting in crystals, therefore: 1. Metals are malleable and ductile
– the layers of ions can slide over each other 2. Metals are good
conductors– free electrons take energy
3 Chemical energetics
3.1 Exothermic reaction: gives out energy to the surroundings
Bond making is exothermic
3.1.1 Combustion of fuels
3.1.3 Adding water to anhydrous
3.1.4 Adding concentrated
sulfuric acid to water
3.2 Endothermic reaction: takes in energy from the surroundings.
Bond breaking is endothermic
3.2.2 Thermal Decomposition
188.8.131.52 Metal carbonates such as calcium
carbonate break down when heated
3.2.3 ethanoic acid with sodium carbonate
3.2.4 Melting, boiling and evaporation. These
are endothermic processes, not reactions
184.108.40.206 Natural gas is burned in homes for cooking
and eating. Also in gas-fired power stations;
the heat is used to boil water to make steam,
which spins turbines for generating electricity
220.127.116.11 Produces carbon dioxide which is linked to global warming
3.3.2 Nuclear fuels: Radioisotopes such as uranium-235;
these are unstable atoms which break down
18.104.22.168 Nuclear fuels are not burned; instead the atoms are
broken down by bombarding them with neutrons.
22.214.171.124 Uranium breaks down to give
smaller atoms such as
lanthanum and bromine atoms:
U-235 → la-145 + Br-88 +
126.96.36.199 Atomic energy is released as heat
188.8.131.52 Nuclear power stations use the heat generated by fission
of a fuel (either uranium or plutonium) to boil water to
make steam. The steam is used to turn a turbine to
184.108.40.206 Harmful radiation is given out when nuclear fuels
break down. The products are also radioactive.
3.3.3 Hydrogen as a fuel
220.127.116.11 Hydrogen reacts with oxygen to produce water plus energy. hydrogen + oxygen → water + energy
2H2(g) + O2(g) → 2H2O(l)
18.104.22.168 Hydrogen can be made from the electrolysis of water. If
the electricity used during electrolysis comes from a
renewable resource (solar power for example) then the
hydrogen fuel produced is also renewable.
22.214.171.124 Hydrogen used as a fuel does not produce pollution or
contribute to global warming because the only product of
combustion is water
126.96.36.199 Hydrogen is explosive and difficult to store.
188.8.131.52 If the hydrogen does not come from a renewable resource but is
made from methane, then the hydrogen fuel produced is also not
184.108.40.206 Fuel cells
220.127.116.11.1 A fuel cell needs to be continuously supplied with both a fuel and oxygen,
which react together to produce electricity.
18.104.22.168.2 A hydrogen fuel cell is made from an anode
and a cathode with an electrolyte contained
between them. The fuel cell generates
electricity. It is not the same as an electrolysis
cell which needs to be supplied with electricity.
22.214.171.124.3 Electrolyte: Potassium hydroxide
Anode and Cathode: Platinum catalyst
126.96.36.199.4 2H2(g) + O2(g) → 2H2O(g)
188.8.131.52.5 Electricity is produced in a form of electric current
3.3.4 Simple cell
184.108.40.206 consists of a negative pole (the more reactive metal) and a positive
pole (less reactive metal) and an electrolyte. The greater the difference
in reactivity of the two metals, the greater the voltage will be. The
electrons flow because one metal is more reactive, so it has a stronger
drive to give up its electrons. The atoms give up electrons and enter the
solution as ions.
3.4 Rate of reactions
3.4.1 Rate of reaction = amount of reactant used ÷ time.
Rate of reaction = amount of product formed ÷ time.
3.4.2 Fill a gas jar with a mixture of hydrogen and oxygen, and cover it. Even if you
leave it for hours, no reaction will happen. Then dip a platinum wire into the mouth
of the jar. The gas mixture explodes immediately with a pop, producing water.
3.4.3 Reactions with different sized particles (e.g. magnesium powder vs. ribbon + acid, marble chips vs. smaller chips).
Time taken for a certain amount of gas to be produced is measured, or change in mass, because the gas escapes
(e.g. hydrogen for Mg + acid reaction, carbon dioxide for marble chip + acid experiment.
3.4.4 Hydrochloric acid and sodium thiosulphate solution are mixed in a flask,
and a stopwatch starts. They react forming sulphur which is insoluble
in water so precipitates. The flask is on top of a cross drawn on a
piece of paper. You measure the amount of time taken for the cross to
not be visible because there is enough sulphur. The diameter of the
cylinder should be kept constant
3.4.5 Large surface area can mean danger: Flour dust, wood dust, custard powder, instant coffee, sugar,
and dried milk have large surface areas, and are combustible. A spark from a machine, or a lit
match, can cause an explosion, this also applies to gases from mines
3.4.6 Increasing the concentration of a substance in solution means that there will be more particles
per dm3 of the substance. The more particles that there are in the same volume, the closer to
each other the particles will be. This means that the particles collide more frequently with each
other and the rate of the reaction increases.
3.4.7 Raising the temperature makes the particles move faster. This means that the particles collide more
frequently with each other and the rate of the reaction increases. Also, the faster the particles are traveling, the
greater is the proportion of them which will have the required activation energy for the reaction to occur.
3.4.8 Increasing the pressure of a reaction where the reactant is a gas is similar to increasing the concentration of a
reactant in a solution. The gas particles (usually molecules) will be closer together when the pressure
increases. This means that the particles collide more frequently with each other and the rate of the reaction