Chemical Equation

Chemical changes are shown using chemical equations

  • One way to show a chemical reaction is to write a word equation.
  • It’s not as quick as using chemical symbols and you can’t tell straight away what’s happened to each of the atoms, but it’s dead easy.
    • Here’s an example-you’re told that methane burns in oxygen giving carbon dioxide and water
    • Methane + Oxygen - Carbon Dioxide + Water
    • The molecules on the left-hand side of the equation are called reactants(because they react with each other)
    • The molecules on the right-hand side are called the products(because they’ve been produced from the reactants

\

Symbol equations show the atoms on both sides

  • Chemical changes can be shown in a kind of shorthand using symbol equations.
  • Symbol equations just show the symbols or formulas of the reactants and products
    • Magnesium + Oxygen - Magnesium Oxide
    • 2Mg + 02 - 2Mg0

Symbol equations need to be balanced

  • There must always be the same number of atoms on both sides-they can’t just disappear
  • You balance the equation by putting numbers in front of the formulas where needed.
    • Take this equation for reacting sulfuric acid with sodium hydroxide:
    • H2S04 + Na0H - Na2S04 + H20
  • The formulas are all correct but the numbers of some atoms don’t match up on both sides
  • You can’t change formulas like H2SO4 to H2SO5. You can only put numbers in front of them.
  • The more you practise, the quicker you get, but all you do is this:
    • Find an element that doesn’t balance and pencil in a number to try and sort it out
    • See where it gets you. It may create another imbalance, but if so, pencil in another number and see where that gets you
    • Carry on chasing unbalanced elements and it’ll sort itself out pretty quickly

\