TutorForAll

Science 7–10 · Year 10

Metals competing for salts: building a reactivity series on a spotting tile

Reactions

PracticalLow risk

The idea

A more reactive metal displaces a less reactive metal from a solution of its salt, so a grid of metal-against-salt tests orders the metals.

Safety card

Low riskAn adult supervises

Hazards

  • copper(II) sulfate causes eye damage and is toxic to aquatic life
  • magnesium and zinc are flammable
  • sharp metal edges

Controls

  • eye protection
  • metal pieces issued by the teacher; no flames
  • tile rinsed into the labelled metal-waste beaker

Note

NSW Department of Education, Chemical Safety in Schools (CSIS) 2021 Technical Update: Section 1.7 (risk assessment before use) and Volume 2 Appendix D (generic assessment advice, user codes and DoE categories). Complete a RiskAssess or CSIS site-specific risk assessment before the lesson.

What you need

  • metal samples about 1 cm each, four of each: copper turnings, magnesium ribbon, iron filings or small nails, zinc granules
  • salt solutions 0.1 mol/L, about 5 mL each: copper(II) sulfate, magnesium sulfate, iron(II) sulfate (fresh), zinc sulfate
  • spotting tile (4 by 4), dropping pipettes, hand lens, stop clock

How to do it

  1. Label the rows with the four metals and the columns with the four salt solutions.
  2. Add 5 drops of each solution to the wells of its column, then one piece of the row metal to each well of its row.
  3. Observe for 5 minutes with the hand lens; record a reaction as a coating forming on the metal or the solution colour fading, and record no change as a dash. Bubbles do not count: some of the solutions are slightly acidic, so hydrogen bubbles can appear on magnesium without any metal being displaced (RSC).
  4. Count the reactions for each metal and order the metals from most to least reactive; check that the order is the same read by rows and by columns.

What you should see

Magnesium reacts in the copper, iron and zinc solutions (3 reactions); zinc reacts in copper and iron solutions (2); iron reacts only in copper sulfate (1); copper reacts in none (0). Copper appears as a brown-pink coating and the blue of copper sulfate fades where copper is displaced. No metal reacts with a solution of its own salt. The learner knows it worked when the grid is a clean staircase: magnesium, zinc, iron, copper.

What changes

What you change
metal and salt solution pairing
What you measure
whether a reaction is observed
What you keep the same
  • solution concentration and volume
  • metal size
  • time watched
  • temperature

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • The metal dissolves rather than swaps places with another metal.
  • A reaction happens between any metal and any salt.
  • The blue colour fading means the solution is being used up like a fuel.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Sources

The pages the author read to write this activity.

  1. curriculum.nsw.edu.au/learning-areas/science/science-7-10-2023/outcomes
  2. edu.rsc.org/experiments/displacement-reactions-between-metals-and-their-salts/720.article
  3. edu.rsc.org/ideas/5-ways-to-teach-displacement-reactions-effectively/4017712.article
  4. education.nsw.gov.au/content/dam/main-education/asset-management/chemical-safety/5._Volume_2_Appendices.pdf

All Concept Studio activities