Atoms, Elements and Compounds
- all substances are made from them
- 100 different types
- combine to make substances
- made up of tiny central nucleus with electrons around it
- a substance made up with one type of atom
- elements can have different properties (e.g. gas, solid, liquid)
- a substance made up with 2 or more different type of atoms
Limestone and its uses
- made up of calcium carbonate (CaCo3)
- formed by the remains of tiny animals and plants
- Cement - Limestone is mixed with clay and heated strongly, the product is powdered.
- Glass - Made from Limestone, sand and sodium carbonate
- Concrete - Mixing cement with sand, stones and crushed rock then adding water.
- Mortar - Made with cement and sand (will set in wet conditions)
- To neautralise acidic soil
A rotary lime kiln
A rotary lime kilm produces QUICK LIME - hence the name lime kiln
calcium carbonate ----> calcium oxide (quicklime) + carbon dioxide
- metals are found in the Earths crust
- a metal ore is when there is enough of a metal or metal compound in the rock to make it worth extracting
- some metals can be found in their native state (as the metals themselves)
- The reactivity series is useful when deciding the best way of extracting each metal from its ore
the reactivity series
- we extract iron from its iron ore by reducing it with carbon in a blast furnace
- the materials needed to make iron, are iron ore, coke and limestone - another use
- hot air is blown into the blast furnace --> coke burns which heats the furnace and forms carbon dioxide C+O2 ---> CO2
- as the temperature increases in the blast furnace, this carbon dioxide reacts again with the coke to form carbon monoxide gas CO2+C ---> 2CO
- the carbon monoxide reacts with the iron oxide, removing it oxygen, and reducing it to molten iron. htis then flows to the bottom of the iron furnace Fe2O3 + 3CO---> 2Fe+3CO2
The iron Furnace
Properties of Irons and Steels
Pure iron is a soft metal that mends easily because of the alignment of atoms which are in layers and able to slide over each other
- Steel is an alloy of Iron - they are mixtures that contain other compounds
- its other elements change the regular structure and so changing its properties
- the simplest steels are the carbon steels
- Carbon Steels contain small amounts of carbon in steel; this makes it harder but more brittle
- high carbon steel , with a relativeley high carbon content , is strong but brittle.
- low carbon steel is soft and easily shaped (maluable) however less likeley to shatter
brittle - Likely to break, snap, or crack, as when subjected to pressure but its usually hard
Low and High alloy steels
Low alloy steels
- are more expensive than carbon steels
- examples are nickel and titanium (always best to know a few incase asked in a question)
- each low alloy steel is altered to suit a particular use
High alloy steels
- MORE expensive than low alloy steels because they contain a much higher percentage of other metals
- an example - chronium-nickel steels or more commenly known as stainless steel (they do not rust)
in alloys the layers cannot slide over eachother easily because atoms of other elements change their regular structure
alloy= a metal that contains other elements
- they are found in the center of the periodic table in groups 2 and 3 - many of them have similar properties
- they are good conductors, hard, tough, strong and malleable
- their strength makes them good construction materials
- their conduction makes them useful for electric wireing
- an example is copper
- there are 2 main methods of extracting copper from its ore : 1 - we use sulphuric acid to produce copper sulphate solution, before extracting the copper, 2. smelting
Smelting - heat the copper ore very strongly in air to produce crude copper. then we use the inpure copper as anodes in electrolysis cells to make pure copper.
prosessing copper ore uses huge amounts of enegy and costs a lot of money. the heat in smelting requires a large amount of energy
Aluminium and Titanium
- both have low densisties compared to other metals
- they resist corrosion
- tiitanium is strong at high temperatures
- Aluminium is a good conductor of heat and can be shaped or drawn into a wire.
- Aluminium is not strong but it can be used in alloys to improve its strength
- Extracting these are expensive because it involves electrolysis and high temperatures; Titanium: Displaced by sodium
- Recycling aluminium saves resources and energy needed to extract the metal from its ore.
Contains different compounds that boil at different temperatures
Distillation is used to separate liquids with different boiling points
Most of the compounds in crude oil are hydrocarbons; many of these are alkanes with the general formula CnH2n+2
- examples : CH4 (methane) C2H6 (ethane) C4H10 (propane)
Alkanes contain as many hydrogen atoms as possible in each molecule so we call them saturated hydrocarbons.
You need to know these fro the exam
- Crude oil is separated at refineries by fractional distillation
- Crude oil is vaporised and fed into a fractionating column. This is a tall tower that is hot at the bottom and cooler at the top
- Hydrocarbons with the smallest molecule have the lowest boiling points and so are collects as the top of the tower and the fractions collected at the bottom have the highest boiling points
- Fractions with low boiling points burn more easily, more useful as fuels.
Refinery - 50 (oc)
Diesel Oil then at the bottom is residue
- Burning hydrocarbons in air produces carbon dioxide and water
- In a limited supply of air, carbon monoxide and particles may be produced because not all the hydrocarbons will burn
- Fossil Fuels contain sulfur compounds when the fuel burns it produces sulfur dioxide.
- high temperatures allows nitrogen and oxygen to react making nitrogen oxides. they are poisonous and can trigger some peoples athsma and cause acid rain.
- hydrocarbons with big molecules hen burnt make particulates as not all of the long hydrocarbon molecule cannot be burnt