Chemistry
Differentiate between a physical change and a chemical change with reference to-
(a) Nature of change i.e., temporary and reversible or permanent and irreversible.
(b) Formation of products.
(c) Energy changes taking place during the respective change.
Phy & Chem Changes
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Answer
| Characteristics | Physical change | Chemical change |
|---|---|---|
| Nature of change | A physical change is a temporary and reversible change. E.g., Water on freezing converts to ice and ice on melting converts back to water | A chemical change is a permanent and irreversible change. E.g., lead dioxide gets permanently converted to lead monoxide on heating. |
| Formation of products | In a physical change, no new substances are formed. E.g., Water on freezing converts to ice and no new substance is formed. | In a chemical change, new substances are formed. E.g., on heating lead dioxide two new substances are formed, lead monoxide and oxygen. |
| Energy changes | Physical change is not accompanied by a marked evolution or absorption of heat. E.g., no energy change is seen during conversion of water to ice. | Chemical change is accompanied by a marked evolution or absorption of heat and sometimes emission of light. E.g., when a magnesium wire is heated, light energy is evolved. |
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