Chemistry Notes PDF

Chemistry Atom structure Atom- smallest part of an element 3 sub-atomic particles are: Electron mass- charge -1 mass 0 Neutron mass- charge 0 mass 1 Proton mass- charge 1 mass 1 Electrons have 2 in the first shell then 8 on the second Isotopes have the same atomic number but they hav...

Chemistry Atom structure Atom- smallest part of an element 3 sub-atomic particles are: Electron mass- charge -1 mass 0 Neutron mass- charge 0 mass 1 Proton mass- charge 1 mass 1 Electrons have 2 in the first shell then 8 on the second Isotopes have the same atomic number but they have different mass numbers. Compounds are formed during chemical reactions Oxygen + magnesium= mangnesiumoxide Ionic bonding is where a metal reacts with a non- metal Covalent bonding is where a non-metallic element reacts with a non-metal element Distillation- separation of two liquids with two different boiling points Evaporation- sperate solutes from solutions Chromatography-to separate solvents in a solution (different dyes in ink) History of the atom Dalton theory- tiny spheres Thomsons model-electrons, plum pudding Rutherford's model- charge at the nucleus Bohr's model- electrons orbit the nucleus Periodic table- according to their atomic weight Groups are in collum's Rows are periods Non-metals are on the right Metal is on the left Metals are: high melting and boiling points, high density, malleable, ductile Non-metals are: low density, low melting and boiling points, non-ductile, brittle Group 1 are alkali metals they increase in reactivity, low melting points, have 1 electron on the outer shell, Group 0 are noble gases they have a full shell of electrons and are unreactive their boiling point increases as you move down the column. Non- flammable and are colourless Group 7 are halogens and decrease in reactivity. They are non-metals they have 7 electrons on their outer shell. Low boiling and melting points. Poor conductors Ionic bonding is where you normally transfer electrons to another element to get 2 full shells Ionic compounds have high melting and boiling points and are brittle and conduct electricity. Thye have a giant ionic lattice structure. Covalent compounds contain non-metals bonded together Molecular substances form where two or more atoms are joined together by covalent bonds Giant covalent structures are diamond graphite and silicon dioxide Melting boiling/evaporation Sold liquid gas Freezing condensation Exothermic reactions where a chemical reaction occurs, energy is transferred to or from surroundings. E.g. bonfire Endothermic reactions where a chemical reaction occurs, they take in energy from the surroundings. E.g. photosynthesis Bond energy is like H=H 436 C=H 413 Crude oil is a fossil fuel and can form over millions of years from the remains of biomass that was buried in mud. Organisms die and fall to see bed They get covered in layers of mud Mud turns into rock and organisms' decay to form crude oil Alkanes contain a single covalent bond. End in any ane Properties: temperature at which the liquid boils Tendency turns into gas How easy it flows how easily it burns Low density Lighter than water No colour Combustible Fractional distillation- different hydrocarbons have different boiling points because they have different size molecules 40c- domestic cooking and heating 80c-petrol fuel for cars 150c-naptha 180c-keroscene fuel for aircraft 260c-diesel oil 340c-residue for roads Combustion of hydrocarbons is- Hydrocarbon+oxygen carbondioxide+carbonmonoxide+carbon+water Particles can be inhaled causing respiratory problems and can produce soot in the atmosphere and can block sunlight Cracking is breaking down a longer hydrocarbon chain a smaller one so the smaller one can be used for fuel Early atmosphere was formed 4.5 billion years ago Carbon dioxide, water, methane, ammonia spued out of volcanoes Carbon dioxide dissolved into oceans Plants photosynthesised and gave out oxygen Dead plants created fossil fuels and form coal Dead fish was made into crude oil and made into gas oil There was no oxygen in the early atmosphere but now there is 21% There was some ammonia in volcanoes in early atmosphere and now there is none There was lots of carbon dioxide in the early atmosphere in volcanoes and now there is 0.04% There was little nitrogen in the early atmosphere but now there is 78% There was some methane in volcanoes in the early atmosphere but now there is none There was lots of water in volcanoes in early atmosphere and now there is 1% Greenhouse gases are made out of carbon dioxide, methane and water vapour Gases in the earth's atmosphere that trap heat Sun emits short wavelengths infrared waves Most of these penetrate the atmosphere and reach the earth where they are either reflected or absorbed Reflected waves have a longer wavelength Longer wavelength radiation is trapped by the atmosphere, warming the earth Greenhouse gases rise by: Burning fossil fuels (release carbon dioxide, water vapour) Deforestation (carbon dioxide removed) Rice paddies (releases methane) Cattle farming (releases methane) Landfill (releases methane) Climate change: Change in snow Strong storms Damaged corals Rising sea levels Heat waves More wildfires Warmer oceans Reducing carbon footprints: Eating less red meat Switching to renewable resource Walking Recycling Carbon dioxide is used for a gas hob and complete combustion. Can cause global warming Carbon monoxide- produces by incomplete combustion. It is poisonous as it reduces ability of blood to carry oxygen Soot-produced by incomplete combustion and small particles of unburned carbons. Can cause global dimming and breathing problems. Lung cancer, asthma Sulfur dioxide- when fuels are burned it reacts with oxygen in the air. Can cause acid rain Nitrogen oxides- formed by the reaction of nitrogen and oxygen in the air inside hot engines can cause acid rain.