OCR Gateway C1
Atoms, Molecules and Compounds
Atoms
Displayed and Molecular Formula
A molecular formula is written as H2O, and represents the number and type of atoms in a molecule.
A displayed formula shows the atoms and bonds in a molecule in a visual form.
If a formula has brackets around it, and a number after, it means x lots of that molecule.
You can construct molecular formulas from displayed formulas, and sometimes displayed from molecular.
Chemical Equations
Word equations represent reactions using words, whereas symbol equations show the atomic equations. Symbol equations MUST BE BALANCED
Emuslifiers, Cooking and Chemical Change
Emulsifiers
Hydrophilic head - likes water, hydrophobic tail - hates water
Tail in oil, head in water, additionally they keep a oil droplet seperate from the others.
Additive, helps keep oils together with water in a emulsion.
Cooking #
Different foods are cooked for different reasons, digestion, remove poison, improved taste/texture etc.
Chemical Changes
Mostly cannot be reversed.
Thermal Decomposition: Breaking down of a substance into simpler substances when heated.
Baking powder: 2NaHCO₃ -> Na₂CO₃ + CO₂ + H₂O
Carbon Dioxide Test: Limewater turns cloudy.
Perfumes, Kinetic Theory and Forces between Particles
Perfume
Contains Esters, made by acid+alcohol with a side product of water
Perfumes need properties such as easily evaporating, not being toxic, and being unable to react or dissolve in water
Need testing before use, to make sure they are safe to be used.
Solids, liquids and Gases
Strong attraction between particles in a solid, medium in a liquid and littlle to no in a gas. Solids keep a shape, liquids fill the bottom of a container, and gases fill an entire container no matter what
Volatility (ease of evaporation) is key to smelling something, the more volatile it is the more we smell.
Solutions
Mix of Solvent (Liquid) and Solute (Solid)
Some materials can be soluble in one solvent but not in another, based upon force of attraction between molecules of eachother, and itself.
Paints and Pigments
Colloids, mixture of really small particles dispersed in a liquid
Pigments give paints color, binding medium carrys pigment and holds it to the material, solvent thins paint
Oil paints have 2 stages of drying, solvent evaporates and then oil is oxidised. Emulsion just has evaporation
Thermochromic pigments change color based on tempurature, Phosphorescent pigments glow in the dark
Monomers and Polymers
Polymers are formed when unsaturated monomers join together into a chain, called addition polymerisation.
Plastics are an example of polymers
Polymers have different properties, and can be used for different purposes
GORETEX is breathable but waterproof, so is useful, uses laminated PTFE etc
Hydrocarbons
Alkanes/Alkenes
Alkanes are all saturated, with no double bonds, and have hydrogen and carbon atoms, in the formula C(n)H(2+2n)
ONLY CONTAIN HYDROGEN AND CARBON ATOMS
Alkenes have a double bond between carbon atoms, so are unsaturated.
Bromine Water can be used to test, if it turns colorless an unsaturated alkene is present.
Fractional Distilation
Longer hydrocarbon chains have a higher boiling point, are less flamable, more viscous and less volatile.
Fractional Distillation involves the boiling of crude oil, then letting it cool as they rise, seperating them into the relevant fractions.
70+: Bitumen, ~40: Oil, ~20: Diesel, ~15: Kerosene, ~10: Naphtha, ~8: Petrol, ~3: LPG
Cracking
Using a catalyst, and a very high temperature, you can crack a hydrocarbon and you can get a shorter Alkane molecule, and a alkene molecule
Helps to meet the supply and demand of different fractions
Carbon Chemistry
Fossil fuels
Limited supply, enviromental impact, political and enviromental problems, crude oil is at the core of most of these fuels.
Complete and incomplete combustion
Complete produces water and carbon dioxide from a hydrocarbon and water
Incomplete also releases carbon monoxide and carbon, and happens if there is not enough oxygen to go round.
Tested with limewater turning milky
Atmosphere changes, volcanoes gave carbon dioxide, then plants produced oxygen, then ozone allowed complex animals to evolve
Carbon Cycle / Pollution - Biology mind map