Reacting metals with acids

Aims

In this practical students will:

  • react four different metals with an acid to decide which reacts most vigorously
  • make observations of the reactions to decide how vigorously the reactions are occurring.

Students will be working scientifically to:

  • interpret observations and data, including identifying patterns and using observations, measurements, and data to draw conclusions
  • present observations and data using appropriate methods, including tables and graphs
  • make and record observations and measurements using a range of methods for different investigations; and evaluate the reliability of methods and suggest possible improvements
  • use appropriate techniques, apparatus, and materials during fieldwork and laboratory work, paying attention to health and safety.

Students will be using the following literacy skills:

  • explaining observations in metal–acid reactions and suggesting relative reactivity of different metals.

Teacher notes

  • Students will need to have seen the test for hydrogen using a lit splint before attempting this practical.
  • Students will need to be familiar with what happens when metals react with acids before trying to answer the questions in this task, and should be aware of how to construct word equations.
  • Extending students will be required to construct formula equations for the reactions seen. They will not be required to work out the formulae for the salts, so these have been provided for them on the sheet.
  • Try and provide similarly sized pieces of all the metals so that students can make fair comparisons between the reactions they see.
  • The skill sheet Recording results is available on Kerboodle to support students with designing a table for their observations.

Answers

Hypothesis

Bubbles/fizzing will be seen, as hydrogen is a gas. Students may go on to state that this gas would produce a squeaky pop if lit with a splint.

Questions

1Bubbles/fizzing; temperature change (if the test tube was felt to get hot); the metal disappears or ‘gets used up’.

2lead, iron, zinc, and magnesium
The more reactive the metal with the acid, the more it bubbled.

3Place an empty test tube over the reaction and collect any gas produced. Then hold a lit splint to the mouth of the upturned tube. If hydrogen gas is present, a squeaky pop will be heard.

4magnesium + hydrochloric acid → magnesium chloride + hydrogen

zinc + hydrochloric acid → zinc chloride + hydrogen

lead + hydrochloric acid → lead chloride + hydrogen

iron + hydrochloric acid → iron chloride + hydrogen

Extension

1The heat of the lit splint causes hydrogen to react with oxygen.

hydrogen + oxygen → water

2H2 + O2→ 2H2O

2A large amount of hydrogen would be highly explosive, and therefore dangerous to ignite.

3Mg + 2HCl → MgCl2 + H2

Fe + 2HCl → FeCl2 + H2

Zn + 2HCl → ZnCl2 + H2

Pb + 2HCl → PbCl2 + H2

4Exothermic. Magnesium and hydrochloric acid. Magnesium reacts more vigorously with hydrochloric acid than zinc. It will release more energy, and hence get hotter, during the reaction.

Support sheet

The accompanying support sheet is contains a table for students to record their observations.

Technician notes

Safety

  • Hydrochloric acid is corrosive.
  • Iron filings can be irritating to eyes. Do not rub your eyes with your hands.
  • Lead is toxic. Wash hands after handling.
  • Eye protection should be worn.
  • Take care when handling test tubes as they can become hot and bubble during the experiment.

Equipment and materials

  • eye protection
  • 0.5 M hydrochloric acid (CLEAPSS Hazcard 47A)
  • pipettes
  • test tubes
  • zinc metal pieces
  • lead metal pieces (CLEAPSS Hazcard 56)
  • iron filings (CLEAPSS Hazcard 55A)
  • magnesium ribbon pieces, about 2cm in length
  • splints
  • heatproof mats
  • test-tube racks
  • optional: Bunsen burner (for testing for hydrogen gas)

© Oxford University Press 2014

This resource sheet may have been changed from the original.