2.2.1

Chemical Reactions

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Chemical Reactions

A chemical reaction is when the atoms in an element or compound are rearranged and connected together in a different way.

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Chemical reactions

  • In a reaction, the substances you have at the start are called the reactants.
  • The reactants' atoms are broken apart and then reconnected in a different order to make something new.
  • The new substances are called the products.
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Equations

  • Each element or compound can be represented either by a word or a formula (symbols).
  • There are two types of chemical equations: word equations and symbol equations.
  • A chemical equation is always shown with the reactants on the left of an arrow and the products on the right.
    • E.g. reactants → products
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Equations

  • If there is more than one reactant or product, then they are written with '+' signs between them.
  • There can be any number of reactants or products - it all depends on the chemicals involved.
  • It is important to remember that the little number in a formula tells you how many of each atom you have and that the little number goes on the right of an atom.
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Examples

  • Water:
    • Word equation: oxygen + hydrogen → water
    • Symbol equation: O2 + 2H2 → 2H2O
  • Burning methane:
    • Word equation: methane + oxygen → water + carbon dioxide
    • Symbol equation: CH4 + 2O2 → H2O + CO2

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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