8.4 Reactions of Metals with Water

• Reactions of sodium and potassium with water

  • some metals are too reactive for you to test in water
  • sodium and potassium react very vigorously
  • metal reacted with water to produce hydrogen and metal hydroxide
  • word equation: metal + water - metal + hydroxide + hydrogen
  • potassium is slightly more reactive than sodium. The hydrogen gas is ignited (catches fire) in an instant
• Reactions of other Metals with Water

  • some metals react less vigorously with water
  • ex: calcium and magnesium
  • in an experiment, the hydrogen gas given off is collected in an inverted tube by the method of displacement of water
  • to improve the experiment to obtain measurable results, the test tube can be replaced with a measuring cylinder
• Reactions of other Metals with Water

  • some metals react with steam
  • magnesium will react more rapidly with steam than with water
  • the magnesium ribbon and soaked cotton wool are heated. Magnesium reacts with water in gas. Hydrogen gas is produced and can be ignited
  • Word equation: magnesium + water(g) - magnesium oxide + hydrogen
  • however, some metals, such as copper, platinum, gold, and diamond, do not react with water at all as they are inert to water
• Reaction between steam and magnesium than between water and magnesium (using particle theory)

  1. steam (gas) has a higher temperature than the water, so it has a higher thermal energy
  2. the gas particles have more kinetic energy than liquid particles
  3. the gas particles collides with magnesium (solid) more often than the liquid particles