The bombardier beetle has an explosive chemical defence mechanism. The reaction that occurs in its abdomen is a catalysed exothermic reaction

This resource accompanies the Education in Chemistry article Wonder weapons where you can read about even more bugs with chemical superpowers.

  • Composite image showing a cartoon image of three insects and the superbugs and their chemical reactions student sheets and teacher notes.

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    Download the unscaffolded student worksheet as MS Word or PDF and the scaffolded student worksheet as MS Word or PDF.

    Download the teacher notes, including answers, as MS Word or PDF.

Learning objectives

  1. Draw an energy level diagram for both a catalysed and uncatalysed reaction.
  2. Explain the effect of catalysts on the profile of a reaction.


Energy changes in reactions can be described as exothermic and endothermic. Endothermic reactions absorb energy from the surroundings and exothermic reactions release energy to the surroundings.


Source: © Nature Production/Nature Picture Library

A bombardier beetle protecting itself by ejecting a boiling, noxious chemical spray, Japan

There are lots of examples of animals across nature which rely on chemicals or a mixture of chemicals to help them avoid being eaten. Some spray acid whereas some spray oils. However, the bombardier beetle is slightly different. In this activity learners will read an excerpt from the article Wonder weapons published in Education in Chemistry and then use their knowledge to answer questions on exothermic reactions, the effect of catalysts and balancing equations.


There are two differentiated versions of the student worksheet. In the unscaffolded version, learners are expected to be able to draw a sketch graph including their own axes. In the scaffolded version, the axes are already drawn, as are the start and end points. Learners will add labels to the axes and complete the reaction profiles. Further scaffolding includes fill-in-the-gap answers, while the unscaffolded worksheet requires learners to write their own sentences.

Answers covering both worksheets are provided in the teacher notes.

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