How does a student know that a chemical reaction has occurred?

Md Ariful Islam

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Md Ariful Islam

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And typically chemical change is accompanied by a colour change, or by the formation of an insoluble precipitate or by the evolution of a gas. Some chemical reactions are more obvious than others.

You won't be asked to interrogate a process to which you haven't been introduced. Most of the time, designation of a reaction as chemical or physical is pretty clear:

$CO_2(s) rarrCO_2(g)$

$CH_4(g) + 2O_2(g) rarr CO_2(g) +2H_2O(l)+Delta$

In general chemical change is characterized by the formation of new substances and the making and breaking of strong chemical bonds. Physical changes are largely .

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