atoms and elements
- is in the middle of the atom.
- contains protons and neutrons.
- protons are positively charged and neutrons have no charge.
- is extreemely small compared to the whole atom, however makes up almost the whole mass of the atom.
- These move around the nucleus within the shells.
- They are very small and is around 1/2000 of a proton.
- they circle the nucleus, protons and neutrons on a very long journey for their size.
- these consists of only one type of atom
- are the number of protons in the nucleus and this decides what atom it is.
compounds and mixtures
Compounds are two or more elements chemically bonded together and mixtures are elements which are not chemically bonded.
- When different elements react atoms form chemical bonds with each other to form compounds.
- Making bonds involve atoms giving away, taking or sharing electrons, this makes it very difficult to separate atoms.
- The properties of compounds are totally different from the properties of the original elements.
- compounds can be small molecules like water or large lattices like sodium chloride.
- there is no chemical bond between the different part of a mixture.
- the parts can be separated physically like: water in sand.
CaCO3 Limestone is mainly calcium carbonate •CaCO3 → CaO + CO2 when heated it thermally decomposes to make calcium oxide (quick lime) and carbon dioxide •CaO + H20 → Ca(OH)2 quicklime reacts with water to produce calcium hydroxide (slaked lime)
Slaked lime is an alkali and can be used to neutralize things Limestone is a grey/white colour and is often formed from sea shells. It’s quarried out of the ground. It is great for making into blocks for building with, carving into statues, heating in a kiln with powdered clay to make cement and crushing into chippings used in road surfacing. Limestone is virtually insoluble in plain water, but acid rain reacts with it and dissolves it away.
advantages and disadvantages of limestone
- widely available and cheap
- products are used to neutralize acidic soils, lakes and rivers
- used in power station chimneys to neutralize sulphur dioxide
- quarrying provides jobs
- crushed up into chippings and used in road surfacing
- heated in a kiln with powdered clay to make cement
- mixed with sand and water to make mortar
- mixed with sand, water and gravel to make concrete
- heated with sand and sodium carbonate then melts to make glass
- quarrying destroys the habitat.
- quarrying makes a very very large hole which destroys landscape and takes thousands of years to recover.
- making things from limestone causes pollution.
properties of metals
- metals consists of a giant structure of atoms held together with metallic bonds.
- the metallic bonds allow the outer electrons of each atom to move freely.
- this creates a sea of free electrons throughout the metal which causes it to be good conductors or heat and electricity.
- strong and hard to break.
- can be bent or changed into different shapes.
- good heat conductor.
- good electricity conductor.
- the strength and the ability to be shaped make them good for buildings and structures.
- good heat conductor so can be used in saucepans etc....
- used in electrical wires because they are good at conducting electricity.
metals from rocks
rocks are made of minerals, they are solid elements and compounds. a metal ore is a mineral which contains enough metal to make it worth wile for it to be extracted.
•Iron ore – haematite (iron oxide) Fe2O3
•Aluminium ore – bauxite (aluminium oxide) Al2O3
•Copper ore – chalcopyrite (copper iron sulfide) CuFeS2
useful products can be made and provides jobs so brings money to the area.
causes noise pollution, scarring of landscape and loss of habitats.
deep mine shafts are dangerous for a long time after the mine has been abandoned.
• Crude oil if formed from the buried remains of plants and animals, it’s a fossil fuel. • Crude oil is a mixture of different sized hydrocarbon molecules. • Hydrocarbons are fuels, they are made of just carbon and hydrogen. As it is a mixture the different molecules aren’t chemically bonded so they keep their original properties like their condensing points. This means crude oil can be split up into its separate fractions by fractional distillation. Each fraction contains compounds of carbon chains with a similar length and condensing point.