AQA SCIENCE C1A)

C1A 1.1 ATOMS, ELEMENTS AND COMPOUNDS

ATOMS

• everything is made of atoms
• there are over 100 types of atom which gives us millions of substances
• atoms are made up of a nucleus with electrons around it
  • the nucleus is made up of neutron and protons
  • protons have a positive charge and electrons have a negative charge
    • the number of protons = number of electrons so atoms have an overall neutral charge

ELEMENTS

• substances made of only one type of atom is called an element
• all elements have their own symbol
• element are put into order of size and grouped by properties in the periodic table

COMPOUNDS

• most substances are compounds
  • this means they are made up of more than one type of atom
• atoms in a compound have chemical bonds making them difficult to separate
  • with ionic, atoms lose or gain electrons to fill their outer shells so become charged which attracts them to oppositely charged atoms
  • with covalent, atoms share electrons to fill their outer shells

C1A 1.2 LIMESTONE AND ITS USES

• Limestone is a rock made mainly of calcium carbonate 
• its chemical formula is CaCO3 

USES

• building blocks - St Paul's Cathedral
• processed into glass
• processed into concrete and cement

PROCESSING

• Thermal Decomposition
  • CaCO3 >>> CaO + CO2
• Lime Kiln
  • this thermal decomposition can be done on a large scale in a rotary kiln

C1A 1.3 DECOMPOSING CARBONATES

• some other carbonates decompose like limestone in a Busen flame

BALANCING EQUATIONS

• Symbols are used in equations to make them simpler and easier to understand internationally
• the same amount of mass must be on either side of the equation
• sometimes numbers are put in front of a molecule's symbol to balance the equation

C1A 1.4 QUICKLIME AND SLAKED LIME

SLAKING LIME

• When limestone is thermally decomposed, one of the products is quicklime
• when water is added to quicklime it makes slaked lime
  • CaO + H2O >>> Ca(OH)2 
  • This reaction is very exothermic
• Dissolving slaked lime in water makes lime water

MORTAR

• made by adding water and sand to slaked lime
• used to hold buildings together because the lime water reacts with the carbon dioxide in the air, turning it to stone

C1A 1.5 CEMENT, CONCRETE AND GLASS

CEMENT

• heating limestone with clay makes cement
• this sets even underwater, unlike mortar
• this makes it much more useful

CONCRETE

• adding crushed stones or rocks to water, sand and cement makes concrete
• concrete is a very strong stone-like material
• pouring it over steel rods makes it stronger and is called reinforced concrete

C1A 2.1 EXTRACTING METALS

• metals are…