Tala and maya are carrying out an investigation into the reactivity of different metals and dilute acids they place a small piece of each metal into a test tube of acid and observe the reaction how can they tell that that a reaction has taken a place

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Explanation:

Many, but not all, metals react with acids. Hydrogen gas forms as the metals react with the acid to form salts. This class experiment is often used in the introductory study of acids to establish that this behaviour is a characteristic property

The experiment is done first on a smaller scale using test tubes (lesson 1 below), with no attempt to recover the salts formed. This establishes that hydrogen production is a characteristic property of the reaction of metals and acids. It can then be done on a larger scale (lesson 2 below), and the salts formed can be recovered by crystallisation.

Lesson 1 is a series of test tube experiments in which each working group establishes as a common feature that hydrogen is given off as metals react with an acid – if the metal reacts at all. This should take around 40 minutes, and most classes should be able to do this version. Each working group needs a small selection of metals and acids to test.

The range of metals and acids tested can be extended to a teacher demonstration in the concluding part of this lesson.

Lesson 2, in which the salt formed is recovered by crystallisation, takes longer, and the class needs to be reliable enough in behaviour and manipulative skills to cope with the hazards involved in heating acidic solutions in beakers on tripods.

The time taken for the reaction depends on the particle size of the metal used. Using small granules helps to reduce the time taken.