chemical reactions

• Rules for writing ionic compounds
• Writing ionic compounds

  • Combine a positive ion with a negative ion
  • Write the positive ion first
  • Write the negative ion second
  • Balance the charges to total zero
• Writing ionic compound formulae

  1. Write ions next to each other

  2. Remove +/- signs

  3. Cross over charges

  4. Write subscripts as needed
• Monatomic ions


  Ions made of one atom
• Polyatomic ions


  Ions made of more than one atom
• In a physical change, no new substance is formed
• Physical changes

  • Changing shape
  • Dissolving sugar in tea
  • Changing state
• In a chemical change, a new substance is formed
• Signs of a chemical change

  • Permanent color change
  • Gas production
  • Formation of a precipitate
  • Temperature change
• A precipitate is a solid that forms from two solutions mixing
• Exothermic reactions

  Reactions that release energy
• Endothermic reactions


  Reactions that absorb energy
• Chemical reactions occur when compounds or elements react to form different substances
• The substances you start with are reactants and those that form are products
• Writing and balancing chemical equations


  1. Write a chemical equation

  2. Place coefficients to balance

  3. Check each atom on both sides
• There are 5 basic types of chemical reactions
• Types of chemical reactions

  • Combination reaction
  • Breaking down reaction
  • Precipitation reaction
  • Combustion reaction
  • Corrosion reaction
• Combination reaction

  Two or more substances combine to form one new substance
• Breaking down reaction

  One substance breaks down into smaller substances
• Precipitation reaction


  Two solutions mix to form a solid
• Combustion reaction

  A reaction with oxygen that produces energy
• Corrosion reaction

  A reaction that breaks metals down to form other compounds
• Acids are chemical substances that donate hydrogen ions
• Properties of acids

  • Have a low pH
  • Turn blue litmus paper red
  • Taste sour
  • Conduct electricity
• Bases are chemical substances that accept hydrogen ions
• Properties of bases

  • Have a high pH
  • Taste bitter
  • Feel slippery
  • Turn red litmus paper blue
• Acids and metals reaction

  Acid reacts with metal to produce salt and hydrogen gas
• Acids and bases reaction

  Acid and base neutralise each other to form salt and water
• Acids and carbonates reaction

  Acid reacts with carbonate to produce salt, water, and carbon dioxide