Conservation of Mass

• Decomposition reaction


  A reactant is broken down into multiple products
• Decomposition of water into hydrogen and oxygen


  Water --> hydrogen and oxygen
• Ways to tell a chemical reaction is taking place

  • Fizzing
  • Smell
  • Popping noise
  • Colour change
  • Temperature change
  • Seeing sparks or flames
• For any chemical reaction, the total mass of all the reactants will equal the total mass of all the products. Mass is not created or destroyed in chemical reactions. This is the law of conservation of mass.
• Magnesium (0.4g) + Oxygen (?) --> Magnesium oxide (0.8g)
• Hydrogen (?) + Oxygen (0.6g) --> Water (0.9g)
• Sodium chloride (?) --> Sodium (1g) + Chlorine (1.3g)
• Carbon (0.55g) + Hydrogen (?) --> Methane (0.75g)
• Balanced symbol equations show 1. The formulae of the reactants and products, 2. How the atoms are rearranged, 3. The relative amounts of reactants and products.
• In a decomposition reaction, the product is broken down into more than 1 reactant.
• Mass is conserved in all chemical reactions.
• One indication that a chemical reaction is occurring is a fizzing or popping noise.
• 2H2 + O2 → 2H2O is NOT a balanced chemical symbol equation.
• In a combustion reaction, a substance burns in oxygen.