Elements in the periodic table can be classified in a number of ways. One of those ways is based on their physical states. While there are numerous solids, there are only some gases and just a few liquids. Regardless, all of them can be further classified and distinguished by their appearance. Apart from that, they can also be distinguished by some very basic chemical reactivity to some standard reagents, such as air, water and acid.


Discrepant Event

(The following task appears in IGCSE Form 4 chemistry as well.)

This is a simple deductive reasoning exercise involving a chemical reaction.

The video below demonstrates an explosive reaction between two gaseous elements. Mixtures of the two gases are contained in different plastic bottle with a rubber bung at the mouth. The reaction is initiated by introducing a lit match next to a small hole on the side of the bottle covered with a small cello (scotch) tape. Watch the video to see and hear the results.

Here is the question:

  1. The two gases in the plastic bottles are colorless and odorless. Deduce the identities of the gases. (All you are being asked to do is use your knowledge of the periodic table and some basic properties about the elements on it.)

Concept involved:

  • periodic table, reactive gases, physical properties, color, odor.

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