Difference Between Physical & Chemical Change
Physical and chemical changes are fundamental concepts in science, particularly in understanding how matter behaves. Here are five key points that illustrate their differences:
1. Definition
- Physical Change: A change that affects one or more physical properties of a substance without altering its chemical composition. Examples include melting, freezing, and dissolving.
- Chemical Change: A change that results in the formation of one or more new substances with different chemical properties. Examples include rusting, burning, and fermentation.
2. Reversibility
- Physical Change: Often reversible. For instance, water can be frozen into ice and then melted back into liquid water.
- Chemical Change: Generally irreversible under normal conditions. For example, once iron rusts, it cannot be reverted back to its original metal form.
3. Energy Change
- Physical Change: Usually involves minor energy changes, such as changes in temperature or pressure without significant release or absorption of energy.
- Chemical Change: Often involves substantial energy changes, either in the form of heat (exothermic reactions) or energy absorption (endothermic reactions).
4. Change in Properties
- Physical Change: The substance retains its original properties. For example, salt remains salt whether it is in solid form or dissolved in water.
- Chemical Change: New properties emerge because the original substances are transformed into different substances. For example, burning wood produces ash and gases, which possess different properties.
5. Examples
- Physical Change: Crushing a can, melting ice, or boiling water.
- Chemical Change: Baking a cake, digesting food, or photosynthesis in plants.
Understanding these differences helps in identifying the types of changes substances undergo in daily life and in various chemical processes.