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Learning objects Check your ions


Explore how a smoke detector works in a home. Make smoke in a kitchen to trigger the beeping sound of a smoke alarm. Look at a circuit diagram and magnified view to see how an isotope interacts with ionised gases within a circuit gap. Test a range of isotopes to see which will work in the smoke detector. This learning object is one in a series of three learning objects.

Educational details

Key learning objectives
  • Students explore the movement of ions in a smoke detector.
  • Students identify isotopes suitable for use in a smoke detector.
Educational value
  • Enables students to explore how a smoke detector works.
  • Provides an animated molecular view of the charged plates in a smoke detector circuit accompanied by a key to molecule types.
  • Explains how the radioactive isotope ionises oxygen and nitrogen, releasing electrons, and why smoke triggers the alarm.
  • Allows students to test the smoke detector with different types of radioactive isotope, with and without smoke, to find out which isotopes are effective.
  • Provides a sample results table to print out.
  • Provides a glossary and topics for further research.
Year level


Learning area
  • science
  • Science/Science understanding
    • Science/Electric circuits
    • Science/Simple experiments
    • Science/Heat
    • Science/Physical properties
    • Science/Safety
    • Analysis;
    • Application;
    • Comprehension;
    • Knowledge
    Student activity
    • Interactives;
    • Experiment;
    • Modelling
    Learning design
    • Experiential learning;
    • Independent learning;
    • Problem solving;
    • Visual learning

    Other details

    • Subject matter expert
    • Organisation: Australian Science Teachers Association
    • Address: Canberra ACT 2600 Australia
    • URL:
    • Technical implementer
    • Publisher
    • Date of contribution: 28 Jan 2014
    • Organisation: Education Services Australia
    • Address: Melbourne VIC 3000 Australia
    • URL:
    Access profile
    • Colour independence
    • Device independence
    • Hearing independence
    Learning resource type
    • Interactive Resource
    • Microsoft Internet Explorer - minimum version: 8.0 (MS-Windows) - maximum version: 9.0 (MS-Windows)
    • Firefox - minimum version: (MS-Windows)
    • Safari - minimum version: 5.1 (MacOS)
    Operating systems
    • MacOS - minimum version: 10.6
    • MS-Windows - minimum version: XP - maximum version: 7
    • © Education Services Australia Ltd, 2013, except where indicated under Acknowledgements.