Question

How can we tell if a chemical change has taken place?

Answer 1

As we know that a chemical reaction usually takes place when one or more than one substances are converted into a new substance and these changes can be made by raising temperature, formation of different colours etc.

Complete step-by-step answer:
As we know that the chemical reaction is that reaction which involves the conversion of reactants into products. And we can identify a chemical reaction by many following ways as given below:
i) A very common and easily seen chemical change that has taken place is when we see a change in the colour of the solution.
ii) Next we can say a chemical reaction has taken place when there is gas formation which we can see through bubble formation in the solution.
iii) Then, if a solid has been formed like crystals formation then also we can say that the chemical reaction has taken place.

Along with these physically visual signs of a chemical change we can also sense if a chemical reaction has taken place or not like:
i) A chemical change can be smelled after a product is formed in the course of a reaction and the smells are generally pungent or deteriorated almond.
ii) Some chemical reactions produce heat energy which can be felt by putting our hands near the apparatus.
iii) We can also hear the chemical reactions like explosions that take place in a reaction. Therefore, the above given examples can be used to confirm a chemical change.

Note: Always remember that the Chemical change is formation of new substance and it can also be predicted by formation of a precipitate which generally forms when two salts are mixed. Also a physical change occurs when there is change in state of a substance which can also be considered as a chemical reaction.