Question

How can we determine that a chemical reaction is taking place?

Answer 1

This can be determined by evolution of gases as in the case of reaction of an acid with a metal where H2 is released.
Evolution of some new smell and light is one way, as in case of burning.

Answer 2

Any of the following observations helps us to determine whether a chemical reaction is taking place-

1) Change in State
2) Change in colour
3) evolution of gas
4) Change in temperature



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