Question

With the help of an activity demonstrate how do we know that a chemical reaction has taken place

Answer 1

There are several observation and activity using which we can tell whether a chemical reaction has taken place or not.
Reaction name : Reaction of Sodium with Water
2 Na + 2 H₂O > 2 NaOH + H2
Activity:
When we put the Sodium piece in water the Sodium melts at 98 degree centigrade and produces heat. the heat is taken by hydorogen gas and it start burning.
If the burning has stopped, it means the reaction has taken place.