Compounds

• What is a chemical bond?

  An attraction between atoms that holds them together to form compounds
• How do the properties of compounds compare to the properties of the elements that make them up?

  The properties of compounds are completely different from the properties of the elements that make up the compound
• What is required to form a compound from elements?

  A chemical reaction
• Give an example of a compound.

  Hydrogen chloride gas
• What happens when iron reacts with sulfur?

  A new compound, iron sulfide, is formed
• What is the characteristic of the melting points of compounds?

  The melting points of a compound are all fixed
• What does a formula represent in chemistry?

  A formula shows the number and type of atoms that make up a compound
• What is the formula for carbon dioxide?

  CO₂
• How many oxygen atoms are in sulfuric acid (H₂SO₄)?

  4 oxygen atoms
• What does the little number outside a bracket in a formula indicate?

  It multiplies everything inside the brackets
• What are some examples of chemical formulas for compounds?

  1. Carbon dioxide – CO₂
  2. Carbon monoxide – CO
  3. Water – H₂O
  4. Sodium chloride – NaCl
  5. Hydrochloric acid – HCl
  6. Carbonic acid – H₂CO₃
  7. Calcium chloride – CaCl₂
  8. Sodium carbonate – Na₂CO₃
  9. Sulfuric acid – H₂SO₄
• How many atoms are in one particle of Na₂CO₃?

  6 atoms (2 sodium, 1 carbon, 3 oxygen)
• What elements are represented in the formula Al₂(SO₄)₃ and how many atoms of each?

  Aluminum (2), Sulfur (3), Oxygen (12)
• What is a symbol equation?

  A representation of chemical changes using symbols or formulae of substances
• What must always be included in a symbol equation?

  There must always be an arrow in a symbol equation
• What is the importance of balancing a symbol equation?

  It ensures that the number of atoms is conserved in a chemical reaction
• Can you change the formulae to balance a symbol equation?

  No, you can’t change the formulae to balance the equation
• What is the first step in finding an element on the periodic table?

  Find an element
• What is the significance of revision in chemistry?

  Revision is important for understanding and retaining chemical concepts
• What is the process for balancing equations?

  Practice balancing equations to improve your skills
• What happens when hydrogen and oxygen react?

  They react to form water
• What are the steps to balance a chemical equation?

  1. Write the unbalanced equation
  2. Count the number of atoms of each element
  3. Adjust coefficients to balance the atoms
  4. Ensure the formulae are correct
  5. Check that the equation is balanced