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Grade 10 Advanced About 20 min Version 1 Awaiting review Premium

Testing the properties of acids and bases

Acids and bases have typical properties that chemists use to recognise them. Acids turn blue litmus red, react with reactive metals such as zinc to give hydrogen gas, and react with carbonates such as marble to give carbon dioxide. Bases (alkalis) turn red litmus blue and turn phenolphthalein pink. In this experiment you test one solution of each with several reagents.

What you will learn

  • Describe the reactions of dilute acids with metals and carbonates.
  • Use litmus and phenolphthalein to tell acids and bases apart.
  • Name the gases produced when acids react with zinc and with marble.

Before you start

  • Know the pH scale. Try "How acidic is it? The pH scale" first.

Materials

  • Dilute hydrochloric acid
  • Dilute sodium hydroxide solution
  • Zinc granules and marble chips
  • Blue litmus, red litmus and phenolphthalein indicator

Equipment

  • 6 test tubes in a rack

Procedure

  1. Put dilute hydrochloric acid in three test tubes and sodium hydroxide solution in the other three.
  2. Add a different test reagent to each tube: zinc granules, marble chips, litmus or phenolphthalein.
  3. Observe each tube and record whether gas is given off or the colour changes.

How this simulation is simplified

  • Each reaction is shown straight away. Real reactions take a few seconds to start.
  • Litmus is shown as a few drops of litmus solution instead of litmus paper.