Physical and Chemical Changes
In our daily life, we observe many changes happening around us — some are temporary while others are permanent. These changes can be broadly classified into two types: Physical Changes and Chemical Changes.
What is a Physical Change?
A physical change is a change in which no new substance is formed. These changes affect the physical properties like shape, size, and state of a substance but do not alter its chemical composition.
Characteristics of Physical Changes:
- No new substance is formed.
- The change is usually temporary and reversible.
- The composition of the substance remains the same.
- It involves a change in state, shape, size, or appearance.
- Melting of ice into water
- Boiling of water into steam
- Breaking of glass
- Dissolving salt or sugar in water
- Cutting of paper or wood
What is a Chemical Change?
A chemical change is a change in which a new substance is formed with different properties. These changes are generally irreversible and involve a chemical reaction.
Characteristics of Chemical Changes:
- A new substance is always formed.
- The change is permanent and usually irreversible.
- Energy is often absorbed or released in the form of heat, light, or sound.
- It involves a chemical reaction and changes in the chemical properties of the substance.
- Rusting of iron
- Burning of paper or wood
- Cooking of food
- Souring of milk
- Digestion of food in our body
Differences Between Physical and Chemical Changes
| Physical Change | Chemical Change |
|---|---|
| No new substance is formed. | New substance is formed. |
| Generally reversible. | Usually irreversible. |
| Affects physical properties only. | Changes chemical composition. |
| Does not involve energy change (mostly). | Often involves energy change. |
| Example: Melting of wax | Example: Burning of wax |
Conclusion
Understanding the difference between physical and chemical changes is crucial in science. Physical changes are often temporary and involve changes in form, while chemical changes create new substances with different properties. By observing everyday events and applying scientific knowledge, we can identify and classify changes around us easily.
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