Chemistry Unit 1
Key Ideas
Atomic Structure
Columns in periodic table are called groups + the groups have similar properties
Protons have positive charge, Neutrons have no charge + Electrons have negative charge
Number of protons + electrons is equal so atoms have no charge
Atomic Number - number of protons/electrons in element + elements are arranged in order of atomic number in periodic table
Mass Number - total number of particles in nucleus in atom (protons + neutrons)
Electron Arrangement
Elements with lowest energy level had the outer shell close to nucleus
Electrons in each shell - 2, 8, 8, 8
Group 1 - have 1 electron in outer shell + react fast with water + oxygen
Noble Gases (Group 0) - unreactive + have full outer shells
Forming Bonds
When a metal reacts with non-metal --metal atoms lose electrons - positively charged + non-metal atoms gain electrons - negatively charged - they are now clled ions
Ionic Bonding - oppositely charged ions attract each other to form a compound that has ionic bonds
Covalent Bonding - non-metals - atoms share electrons + molecules are formed
Rocks + Building Materials
Limestone
used to makes cement + calcium oxide
it is mainly made of calcium carbonate (CaCO3)
Thermal Decomposition
CaCO3 is heated strongly producing Calcium Oxide + Carbon Dioxide
Water is added producing calcium Hydroxide
Add Carbon Dioxide producing CaCO3 + process repeats
Reactions of Carbonates
Metal carbonates decompose to metal oxide + CO2 when heated strongly enough
All carbonates react with acids producing a salt, water + CO2
Limestone is damaged by acid rain as CaCO3 reacts with the acids
Calcium Hyrdoxide = Limewater - turns cloudy if CO2 is present
Cement - limestone + clay is heated in a kiln - it is ground up + mixed with sand + water to make mortar
Concrete - cement + crushed rocks
Transporting limestone can effect environment + quarries affect landscape + appearance
Uses of Metals
Extracting Metals
Ore - rock that contains a large amount of a metal/metal compound
Metals can be extracted by displacement using more reactive element - metals less reactive than carbon are extracted by heating with carbon
Reduction reaction - carbon removes oxygen from the oxide to produce the metal
Iron + Steels
Cast Iron - iron with about 4% impurities - from blast furnace - makes it hard + brittle
Steel - alloy of iron with impurities like carbon
low-carbon steels - easily shaped + high-carbon steels - hard
Stainless steels - have large amounts of other metals in - resist corrosion
Aluminium + Titanium
Aluminium
Titanium
Aluminium - low density, high in reactivity series + resists corrosion
Has to be extracted through electrolysis
Pure aluminium - not strong - aluminium alloys are stronger + harder
Titanium - Resistant to corrosion + strong - low density
Titanium Oxide - reduced by carbon but reacts with carbon - becomes brittle
Extracted from ore - process is expensive - so metal is expensive
Extracting copper
Phytomining - plants absorb copper compound from ground - plants are burned - copper extracted from ash
Bioleaching - uses bacteria to produce solutions containing copper compounds
Electrolysis used to purify it - requires a lot of electricity + heating
Copper compounds can be displaced with metal that is more reactive than copper eg scrap iron
Extracted through smelting - heating ore strongly in furnace - producing impure copper
Useful Metals
Transition Metals
in centre of periodic table - all good conductors of heat + electricity
Many are strong but are malleable - useful in buildings, wiring + vehicles
Copper - good conductor - doesn't react with water - malluable but doesn't stay in shape - good for pipes + water tanks
Copper, Pure iron, Gold + aluminium are soft - often mixed to make alloys
Copper alloys include bronze + brass
Fossil fuels are needed to mine metal ores + it is expensive + uses up limited resources
Crude Oil + Fuel
Fractional Distillation
Bigger molecules at the bottom + smaller ones at the top
Gasoline, Kerosene, Diesel, Fuel Oil, Bitumen - differrent fractions
It condenses at different levels depending on boiling point - higher at the bottom + lower at the top
Oil heated + evaporates - vapour goes up the column
Hydrocarbons - only made of hydrogen + Carbon - alkanes - saturated - single bonds
Burning Fuels
Incomplete combustion - due to oxidisation can produce carbon monoxide + some hydrocarbons might not burn
Oxidisation - Any Fuel + Oxygen = Carbon Dioxide + Water
Fossil fuels contain sulfur compounds - when burnt they produce acid rain (sulfur dioxide)
Cleaner Fuel
Burning any fuel containing carbon produces CO2 + incomplete combustion causes CO - causing global dimming
converters are fitted to car engines to remove CO + NO
Sulfur can be removed from fuels before burning them
Biofuel - made from animal + plant products - renewable + Biodiesel - made from vegetable oils from plants
Products from Oil
Cracking
Breaking down a long chain of hyrdocarbons into smaller molecules
Process - heating a mix of hydrocarbon + steam high OR passing hydrocarbon vapours over hot catalyst
Thermal decomposition in cracking produces a mix of small molecules - some are alkanes + some are alkenes
Alkenes - CnH2n - unsaturated - double bonds - more reactive than alkanes - they react with bromine water turning it colourless
Polymers
Polymers are long chains of monomers - polymerisation is the process forming polymers
Ethene monomers joined together creates the polymer Polythene - double bond in ethene becomes a single bond + the other bonds join together with more monomers
Shape-memory polymers - change back to original shape when conditions change - (Smart Polymer)
Plastic Waste
most plastics aren't biodegradable - wasting landfill space + harming environment
Synthetic Material - Manmade Material
Natural polymers include wool, silk + wood
Ethanol
Fermentation
Sugar from plant material + enzymes in yeast is converted into ethanol and carbon dioxide
Yeast, sugar + water in a conical flask connected to test tube containing lime water with tube
Yeast - living creature - anerobic respiration
Shouldn't be done on mass scale - slow process + lots of fuel required
renewable process
Hydration - Ethene reacted with steam at high temp with catalyst
Plant Oil
Cold Pressing
The liquid produced in filtered to remove any solids
The water + impurities are also removed
oils extracted through crushing plant material (nuts + seeds)
Begins with low temp + pressure applied to the materials
Vegetable Oils - provide nutrients + energy for fuel - steam distillation sometimes used to extract it
Steam Distillation - water is heated + evaporates + mixes with lavender or any other plant + then enter condensation chamber producing water + lavender oil.
Hydrogenation/Hardening - unsaturated oils reacted with hydrogen so they become single bonds - have higher melting points - solid are room temp
Emulsions
Emulsion - tiny droplets of one liquid spread through the other liquid (oil + water) - thicker than either of the liquids
Examples - Milk, cream + ice cream
Oil is always on top as it is less dense than water
Emulsifiers
Hydrophilic head - attracted to water - negative charge + Hydrophobic tail - attracted to oil
Hydrophobic ends always in oil so the oil droplets become surrounded by hydrophillic parts
Emulsifier - substances that help stop oil + water from separating into layers
This stops oil droplets mixing + water + oil sperating
Changing Planet
Plate Tectonics
Earth Structure
From the centre out - Inner + Outer Core, Mantle, Crust, Atmosphere
Crust - thin solid - about 5km to 70km thick - raw materials we need are here, atmosphere + oceans
Mantle - about 3000km thick - almost completely solid - move about 2cm/year
Core - very thick - contains iron + nickel - liquid outer core - solid inner part - extremely hot
Earth has diameter of 12,800km
Crust is in 7 different plates - they move a few cm/year due to convection currents in mantle
Convection caused by energy released by decay of radioactive elements heating in mantle
Magma in mantle heated by core + becomes less dense + rises - gets more dense + drops to get heated by heat from radioactive activites
Subduction - Oceanic crust goes under Continental crust (causing earthquakes) - rock can melt + rise to form volcano
Alfred Wegener - created idea of continental drift in 1915 - not accepted (didn't know why it happened) - Plate Tectonics developed in 1960s.
Atmosphere in Past
Originally Earth was covered in volcanoes releasing CO2, water vapour + nitrogen
When Earth cooled water vapour condensed forming oceans
Early atmosphere was mostly CO2 and some water vapour
Next 2 billion years - algae + plants evelved - used CO2 for photosynthesis + released oxygen - plants increased so less CO2 + more Oxygen
Life on Earth
Nobody knows for sure how plants evolved/where they evolved from - not enough evidence
Miller-Urey Experiment
Used a mix of water, ammonia, methane + hydrogen + high voltage spark to simulate what early life on earth would be like
After a week - amino acids had been produced - building blocks for proteins
Other Theories
The organic molecules produced a Primordial Soup + amino acids combined to make the proteins from which life began
There is no evidene that proves any theory
Scientists have been able to produce amino acids from other mixes of gases
Gases in Atmosphere
Plants used the CO2 + animals ate them so the carbon ended up in sedimentary rock as their remains
Modern composition of atmosphere - Oxygen 21% - Nitrogen 78% CO2 0.04% and Other 0.6%
Fractional Distillation of liquid air - separates gases in air - each have different boiling points - cooled to below -200°C
Carbon Cycle
Plants + animals die - through sedimentation turn into fossil fuels
These fuels are burnt by humans so more CO2 in atmosphere
Animals feed of them + we breath producing more CO2
Decay + respiration by decomposers creates more CO2
CO2 used in photosynthesis
Because of these constant processes the amount of CO2 in atmosphere has stayed the same for past 200 million years