Which of the following are the observations that indicate a chemical change has occurred?
Which of the following are the observations that indicate a chemical change has occurred?
The correct option is D Change of odour
In a chemical change the chemical composition of the substance changes because of the formation of new substances.
Example:- Pb(NO3)2 (s) + Heat−−−→ PbO (s) + SO2 (g) + SO3 (g)
The above example depicts a chemical change (chemical reaction) in which new substances are formed, gases evolve and change of odour is observed.
Change of physical state (Physical change) is a part of chemical change but this observation alone can't indicate that a chemical change has happened.
Example:- H2O(s) Heat−−−→ H2O(l)
(Ice) (Water)
This is an example of a change of physical state (physical change) and no chemical change has happened here because the chemical composition of substance remains the same.
In a chemical change the chemical composition of the substance changes because of the formation of new substances.
Example:- Pb(NO3)2 (s) + Heat−−−→ PbO (s) + SO2 (g) + SO3 (g)
The above example depicts a chemical change (chemical reaction) in which new substances are formed, gases evolve and change of odour is observed.
Change of physical state (Physical change) is a part of chemical change but this observation alone can't indicate that a chemical change has happened.
Example:- H2O(s) Heat−−−→ H2O(l)
(Ice) (Water)
This is an example of a change of physical state (physical change) and no chemical change has happened here because the chemical composition of substance remains the same.
