Chemistry GCSE Unit 1a
Atoms and formula
- Created by: Izzy Keighley
- Created on: 14-03-12 21:44
Atoms and formula
The formula of a compound show the number and type of atoms
Atoms and symbols used to represent substances in chemical reactions
E.g.
H2 = 2 x hydrogen atoms
AlCl3 = 1 x aluminium atom
3 x chloride atoms
Represent a chemical reaction using an equation
Shows how atoms are rearranged to make new products
Always have the same on each side of the arrow (balanced equation)
Thermal decomposition
Process of breaking something down into simpler substances by means of heating
Limewater test - if CO2 is given off the limewater will turn cloudy from clear
When we heat a metal carbonate a thermal decomposition reaction occurs
The same two products always made are a metal oxide and carbon dioxide
Limestone cycle
Thermal decomposition of limestone
Heated in kilns
Calcium carbonate decomposes into calcium oxide and carbon dioxide
Quicklime is vital in cement, concrete and glass
Add water to quicklime and calcium oxide changes to calcium hydroxide
Slaked lime is vital in building materials
Limestone found in the peak district and north of england
Kilns found on side of hills or mountains near a quarry so gravity is used to move the rocks through the ovens
Glass
Limestone is heared with sand and sodium carbonate to make glass
Made mainly from sand
First glass object dated around 4500BC
Raw materials are sand (SiO2), limestone (CaCO3), sodium carbonate (Na2CO3)
Recycled glass makes up to 30% of new glass
Many different types of glass
Windscreens made as thin plastic coated by glass called laminated glass
Types and uses of glass
- Soda lime - windows
- Boro silicate - test tubes, beakers
- Lead crystal - decorative glass, vases
- Glass fibres - fibre optics, fibre glass
- Optical glass - cameras, reading glasses
- Glass ceramic - opaque ovenwear
Uses of limestone
- Glass
- Buildings and roads
- Steel
- Paper
- Neutralisation
- Mortar
Quarrying
Pros
- Provides jobs
- Rock for local uses
- Boosts local economy
- Visitor attraction after use
- Use limestone for products e.g make up
Cons
- Noise pollution from explosions
- Dust ruining landscapes
- Visual pollution
- Puts tourists off
- Busy roads and lorries
- Wildlife affected
- Erosion
Metals and alloys
Solid at room temperature
High melting point
Good conductors of electricity and heat
Malleable; they can be shaped
Ductile; they can be drawn into wires
Strong and dense
Found in the earth's crust combined or uncombined as pure substances
Some unreactive metals found uncombined e.g. gold, silver, copper
Metals found in pure form said to occur as 'native'
Most metals found combined in ores so have to be extracted
Transition metals
Most common type of metals
Exhibit all common properties of metals
3/4 of periodic table is metals and 1/4 is gases
Uses of metals
Aluminium - low density and doesn't corrode
Used for cans and car bodies because it's lighter than steel
Gold - unreactive and malleable, doesn't tarnish or change appearance
Used for jewellery and electronics
Titanium - strong but light and doesn't corrode
Mixed with other metals and used for aerospace, watches and artificial joints
Iron - hard, strong, abundant and cheap
Used in building but rusts easily which changes appearance and safety issues
Copper - good electrical conductor and ductile
Used for electric and phone wires and plumbing as not corroded by water
Reactivity series
Metals above carbon extracted by electrolysis
Metals below carbon extracted by reduction using carbon (coke or charcoal)
Native metals do not need to be extracted
Blast furnaces
Metals have to be extracted from ores using electricity or heat
Metals collected from a blast furnace are impure
Alloys are a mixture of metals designed to improve the properties e.g strength
Atoms in pure iron arranged densly so layers can slide making if a soft metal
Other atoms are different sizes so when added the regular structure distorts
Blast furnaces
Aluminium and titanium
Aluminium - aeroplanes, foil, cans, window frames, cables, pans
99% obtained from the ore bauxite which contains aluminium oxide
Extracted by electrolysis
Andodes made from graphite
Titanium - aeroplanes, turbines, artificial joints
Titanium ore contains titanium oxide
Can't be reduced by carbon because it's too brittle
Firstly converted to titanium chloride
Reducing agent is usually sodium
Reaction carried out in an atmosphere of the noble gas argon
Purifying copper
Copper obtained by reduction is impure
Purified by electrolysis before it can be used in wiring
Related discussions on The Student Room
- Chemistry - How likely am I to receive an Imperial College London offer »
- A Level Exam Discussions 2023 »
- A-level Exam Discussions 2024 »
- Bangor University GCSE Revision guides? »
- GCSE Exam Discussions 2023 »
- Edexcel chemistry unit 2 mixed questions »
- Access course for Pharmacy »
- Urgent Edexcel IAL history help »
- Medicine with a BTEC? »
- Pharmacy/a levels »
Comments
No comments have yet been made