Question

Define a chemical reaction . State foue obvservations which help us to determine that a chemical reaction has taken place.

Answer 1

A reaction in which two particles take place and form New substances by chemical method is know as chemical reaction.
1.Change in state
2.Change in Colour.
3.Evolution of gas.
4.Increasing or decreasing of temprature
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Answer 2

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a process in which two or more substances reacts to form some other new substances with new set of properties is called Chemical reaction. 1)change in colour. Zn+CuSO4------ZnSo4+Cu. the colour of cuso4 changes from blue to pale green. 2)change in temperature.