- A physical change is a kind of change in which no new substance is formed. This is the main property of a physical change. For example melting of ice is a physical change because here water changes its state from solid to liquid.
- It is a temporary change. If we remove the cause of change then the substance will regain its original state. For example when some sugar is dissolved in water, the state of sugar is changed. But if we heat the sugar solution until the whole water is evaporated then we get the sugar back in crystalline form.
- In a physical change, neither energy is evolved nor energy is absorbed.
- The total weight of a substances is same before and after the physical change.
- The chemical properties and composition of the substance do not alter during physical change.
- Alterations in shape, size, volume, physical state, colour and processes like melting, evaporation, condensation, freezing, distillation expansion, contraction, cooling, heating, rain cycle, drying of fruits, magnetization, ringing of electeical bell, sublimation all are physical change.
- A new substance is formed during a chemical change. Formation of a new substance is the main characteristic of chemical change. For example making of curd from milk is a chemical change. Because milk and curd are two different matters.
- Chemical change is a permanent change (except reversible reactions). For example milk can be changed into curd but curd can’t be changed back to milk.
- During a chemical change energy is either evolved or absorbed by the substances. Sometimes light is also emitted.
- The total weight of substances before the chemical change is not same after the chemical change.
- The chemical properties and composition of the substance change after the chemical change.
- Burning, rusting, fermentation, composition reactions, decomposition reactions, allotropic changes, Isomeric changes, dehydration, respiration, carbon cycle, butter turning rancid, ripening of fruits and all chemical reactions are the examples of chemical change.