Question

Give reason :Burning of paper is a chemical change.

Answer 1

Hint:During the physical change of the substance the appearance of the substance changes but the chemical composition of the substance remains unchanged. But during the chemical change of the substance we see that the substance is completely changed into a new substance with a new chemical composition and new chemical formula. So in the chemical change the appearance as well as the chemical composition of the substance is changed.

Complete answer:
The process of combustion is referred to the process of burning the substance in the presence of oxygen. The burning of paper is considered to be a combustion reaction as it involves the chemical change in the substance. This is because when we burn a paper it undergoes the combustion reaction and during the combustion state of the substance it changes from its solid state or liquid state to gaseous state. So the burning of paper is considered as a chemical change as the paper after burning changes into ashes and fumes of gases evolve. On burning paper the white paper changes into a brownish black colour of ashes by evolving some gases.
When the reactants are subjected to undergo chemical reaction for the formation of products, so the reaction will occur either by absorbing the energy or by releasing the energy by forming the product.

Note:The features which we generally observed during the chemical change are the evolution of gas, change in the state of the substance, change in the temperature and change in the colour. If the energy is lost by the reactants to form the product then it is the exothermic reaction. If the reactants gain energy during the reaction it will be considered as an endothermic reaction.