Question

How can we know whether a reaction has taken place or not?​

Answer 1

Answer:

We can tell if a chemical reaction has taken place when one or more of the following things happen:

There has been a colour change inside the reaction flask.

A gas has formed. Usually we know a gas has formed when we can see bubbles. ...

A solid has formed.

Answer 2

Answer:

Reaction has taken place if a new product would be formed or there has been change in the shape, size, colour and density of the object.