GCSE Chemistry 1

These are some basic revision cards on GCSE Chemistry.

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Atoms 1:

  • All things are made of atoms
  • A substance made from only 1 atom is called an element
  • Atoms of each element are represented by a chemical symbol, for example oxygen is represented by an 'O', or Sodium is represented by 'Na'.
  • Atoms have a nucleus in the centre made up of protons and neutrons.
  • The protons and neutrons are surrounded by electrons.
  • The relative electrical charges are:

Protons: +1 Charge

Neutrons: 0 Charge

Electrons: -1 Charge

  • In an atom, the number of protons is equal to the number of electrons, and therefore each atom has a neutral charge (they cancel each other out).
  • All atoms of the same element have the same amount of protons.
  • The number of protons in an element is called the atomic number.
  • The sum of the protons and neutrons equal the element's mass number.
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Atoms 2:

  • Electrons occupy different 'shells' - each electron is in a particular shell.
  • Electrons occupy the innermost shells.
  • The shells can hold a specific amount of electrons:

1st Shell: 2 electrons

2nd Shell: 8 elctrons

3rd Shell: 8 electrons

4th Shell: 18 electrons

(no need for further knowledge for GCSE)

On the next page it is shown how electron shells are drawn for GCSE.

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Atoms 3:

Electron Shell Drawing - Potassium ('K'):

(http://www.gcsescience.com/Potassium-Atom.gif)

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Chemical Reactions 1

  • When elements react, they form a compound.
  • This reaction involves giving, taking, or sharing electrons to form ions or molecules.
  • Ions are compounds that are a mix of metals and non-metals.
  • Molecules are compounds that are made of non-metals.
  • Molecules are held together by covalent bonds.
  • Metals lose electrons to become positive ions.
  • Non-metals gain electrons to become negative ions.
  • These chemical reactions are represented by equations, such as:

CH4+ 2 O2\rightarrow (http://upload.wikimedia.org/wikipedia/en/math/8/3/e/83e37b7246fdfcb99b2754210ebeae27.png) CO2+ 2 H2O

  • No atoms are lost or created during a chemical reaction
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Limestone 1

  • Limestone is mainly composed of Calcium Carbonate (CaCO3)
  • Calcium Carbonate can be decomposed by thermal decomposition (heating)
  • The carbonates of zinc, magnesium, copper, sodium and calcium can be decomposed using the same method
  • Calcium oxide reacts with water to produce calcium hydroxide - an alkali used to neutralise acids
  • Calcium hydroxide then reacts with calcium dioxide to produce Calcium Carbonate
  • Limestone is damaged by acid rain
  • Limestone can be heated with clay to produce cement
  • Cement can be mixed with sand to make mortar, and aggregate and sand to produce concrete.
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