Question

How can we judge that a change has occur ?
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Answer 1

Explanation:

we can judge that a change has occurred if the substance changes it's state, color, odour or there is any evolution of gas, pecipitate is formed.

Answer 2

Answer:

Any subtance that is undergoing or has undergone a change will exhibit 1 or more of these characteristictics: Change in size, shape, state, properties, position or colour.