IGCSE Physical and chemical changes Notes

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Syllabus Objectives

IGCSE Chemistry Revision Notes

Topic:Chemical reactions

Sub Topic: 6.1 Physical and chemical changes

Syllabus Objectives:

CORE:

Identify physical and chemical changes, and describe the differences between them

Revision Notes

IGCSE Chemistry Notes Physical and chemical changes

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Free IGCSE Chemistry Summary Notes Physical and Chemical Changes

Physical Changes

Definition: Physical changes are changes in the state or appearance of matter without altering the chemical composition.
Characteristics:
- Reversibility: Often reversible.
- No New Substance: No new substances are formed.
- Energy Changes: Typically involve changes in energy, such as melting or boiling, but these changes are usually less significant than in chemical changes.
- Examples: Melting, boiling, freezing, dissolving, and breaking.

Chemical Changes

Definition: Chemical changes involve making or breaking of bonds between atoms, resulting in the formation of new substances with different properties.
Characteristics:
- Reversibility: Usually irreversible under normal conditions.
- New Substance: New substances with different chemical properties are formed.
- Energy Changes: Involves significant energy changes, either releasing (exothermic) or absorbing (endothermic) energy.
- Indicators: Color change, gas production, temperature change, precipitate formation, and odor change.
- Examples: Rusting of iron, burning of wood, baking a cake, and digestion of food.

Differences Between Physical and Chemical Changes

Nature of Change:
- Physical: Changes in physical properties (state, shape, size).
- Chemical: Changes in chemical composition, leading to new substances.
Reversibility:
- Physical: Generally reversible (e.g., freezing and melting).
- Chemical: Generally irreversible (e.g., burning, rusting).
Energy Involvement:
- Physical: Often involves less energy change compared to chemical changes.
- Chemical: Involves significant energy changes, either absorbing or releasing energy.
Examples:
- Physical: Melting ice, dissolving sugar in water, cutting paper.
- Chemical: Combustion of gasoline, photosynthesis, souring of milk.