GSCE Science - Chemistry - C1

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Topics

Topics

  • Atoms, Elements, Compounds and Mixtures
  • Separating Mixtures
  • Atomic Model
  • Periodic Table
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Atoms, Elements, Compounds and Mixtures

Atoms, Elements, Compounds and Mixtures

All substances are composed and made up of atoms that cannot be chemically broken down because of their breaking point due to heat. 

  • Elements are made up of one type of atoms. Na - Sodium 
  • Compounds are made up of more than one type of atom. They are formed by chemical reactions, and can only be separated chemically. Hv2O - Water
  • Mixtures are also made up of more than one type of atom. They are formed by physical reactions and can only be separated physically, as they are not chemically joined. Sand and Water
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A - Separating Mixtures

Separating Mixtures

Mixtures can be split and sorted into their two or more elements/compounds as they are no chemical bonds combining them together. They are only physically combined.

  • Solvent - the liquid in which a solute dissolves
  • Solute - the substance that dissolves in a liquid to form a solution 
  • Solution - the mixture formed when a solute has dissolved in a solvent
  • Soluble - will dissolve 
  • Insoluble - will not dissolve 

Mixtures can be separated by filtration, crystallisation, simple distillation, fractional distillation and chromatography. 

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B - Separating Mixtures

Separating Mixtures

  • Filtration - separates substances - insoluble from soluble 
  • Crystallisation - separates soluble solution from a solvent - evaporation - sodium chloride from salt solution
  • Simple Distillation - separates a liquid from a mixture - evaporation followed by condensation - water from sea water
  • Fractional Distillation - separates a mixture - condensation - HBP at the bottom and LBP at the top - works because different substances in mixtures have different boiling points - ethanol from ethanol and water
  • Chromatography - substances - solvents along an absorbent piece of paper - different colours of ink 
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Atomic Model

Atomic Model

Name - Mass - Charge

  • Proton - 1 - +
  • Neutron - 1 - 0
  • Electron - Very Small - - 
  • Atom - 0 - No Overall Charge because the number of positive protons = number of negative electrons

Atoms of different elements have different numbers of protons. 

Electrons are found in the shells. But Neutrons and Protons are found in the nucleus and make it. Electrons orbit around the outside attracted to the positive protons.

Shells = 2, 8, 8

  • Mass Number/Top = Protons and Neutrons
  • Atomic Number/Bottom = Protons  
  • Protons = Atomic Number - Neurtons = Mass Number - Atomic Number - Electrons = Atomic Number
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A - Periodic Table

Periodic Table

Elements with similar properties are in columns known as groups. Rows are known as periods. The group is the number of electrons in the outer shell and the period is the number of shells.

The elements are divided by the staircase separating the metals and non-metals.

  • Metals - shiny, mostly solid, dense, strong, malleable, a good conductor of heat and electricity
  • Non-Metals - dull, low density, weak, brittle, poor conductor of heat and electricity
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B - Periodic Table

Periodic Table

  • Noble Gases - Group 0, Unreactive (because they have a stable arrangement of electrons, full outer shells), single atoms, do not react to form molecules, BP higher down the group
  • Alkali Metals - Group 1, Very Reactive, Low Densities, LMP and LBP (have just one electron in the outer shell, so only need to lose one), Reactivity increases down the group (elections less strongly attracted because of further distance, easier to lose
  • Halogens - Group 7, Reactivity decreases down the group, molecular
  • Transition Metals - Group 2/3, Reactivity decreases across the group, some exceptions, different properties
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