Question

___________ results in the formation of new substances.
A. Physical change
B. Chemical change
C. Both A and B
D. None of the above

Answer 1

Hint:Physical change in a substance is the change in its physical appearance. The shape, state of substance, odor and taste are considered as the physical properties of a substance. The change in physical property only changes its appearance and does not give any new substance.

Complete answer:
New substances formed when breaking of bonds take place and new bonds get formed which results in formation of new products. That breaking of bond is a chemical change because in such a process composition of substance gets changed and forms a new substance. When bonds are broken and new ones are formed a chemical change occurs.
When chemical reactions take place, the atoms get rearranged and the reaction is done by energy change as new products are formed. For example in the reaction between sodium and water to form sodium hydroxide and hydrogen. A lot of energy is released that the hydrogen gas released spontaneously burns in the air. This is a chemical change because the end products are different from the substances before the chemical reaction occurs.
Some common examples of chemical changes are: Ripening of raw mango as during ripening, the external peel color of mango changes from green to a yellowish red color. This happens due to breakdown of chlorophyll which leads to disappearance of green color and development of carotenoids in the peel.
Another example is curdling milk. In curdling of milk the milk gets converted into curd. Chemically the curd forms due to the reaction of lactic acid bacteria and casein.

Hence, option B is correct.

Note:
The chemical changes can be analysed by the following observations such as Change of odor, Change of color (for example, silver to reddish-brown when iron rusts), Change in temperature or energy such as the production or loss of heat. But physical change does not change the composition of substance. Hence it cannot form new substances.