Balanced chemical equations

• What do chemists use to represent elements and compounds?

  Symbols and formulae
• What do word equations and balanced chemical equations represent?

  The changes that happen in chemical reactions
• What is a balanced chemical equation?

  • A chemical equation using symbols and formulae
  • Shows equal number of units of each element on both sides of the arrow
• What is a reactant in a chemical reaction?

  A substance that reacts with another to form products
• What is a product in a chemical reaction?

  A substance formed in a chemical reaction
• What are state symbols in chemical equations?

  • Symbols indicating the physical state of a substance
  • (s) for solid, (l) for liquid, (g) for gas, (aq) for aqueous solution
• What does the state symbol (aq) represent?

  An aqueous solution formed when a substance dissolves in water
• How does H₂O differ in its states?

  H₂O(l) is liquid water, H₂O(g) is steam, and H₂O(s) is ice
• What does the law of conservation of mass state?

  The total mass of reactants equals the total mass of products in a reaction
• What is an atom?

  The smallest part of an element that can exist
• How is mass measured?

  In kilograms (kg) or grams (g)
• What does a balanced symbol equation indicate?

  It has the same number of atoms of each element on both sides of the arrow
• How do you balance a chemical equation?

  1. Check the number of atoms of each element on both sides
  2. Add balancing numbers to the left of the formulae
  3. Ensure equal numbers of each element on both sides
  4. Add state symbols if required
• What is the balanced equation for the reaction between nitrogen and hydrogen to form ammonia?

  N₂ + 3H₂ → 2NH₃
• What do balancing numbers in a chemical equation do?

  They multiply all the atoms in the substance next to them
• What is the key fact about balanced chemical equations?

  • They only show formulae, not names
  • They represent the conservation of mass