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IGCSE Physical and chemical changes Notes

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Test Your Understanding

Physical vs Chemical Changes

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1. Physical Changes

Physical changes are changes in the

________ state

________ appearance

of matter without altering the

________ chemical composition

Physical changes are often

________ reversible

________ new substances

are formed in a physical change.

Physical changes usually involve changes in

________ energy

, such as melting or boiling.

Examples of physical changes include

________ melting

________ boiling

________ freezing

________ dissolving

, and

________ breaking

2. Chemical Changes

Chemical changes involve

________ making

________ breaking

of bonds between atoms.

They result in the formation of

________ new substances

with

________ different

properties.

Chemical changes are usually

________ irreversible

under normal conditions.

Chemical changes involve

________ significant

energy changes.

Indicators include

________ color change

________ gas production

________ temperature change

________ precipitate formation

, and

________ odor change

Examples include

________ rusting

of iron,

________ burning

of wood,

________ baking

a cake, and

________ digestion

of food.

Syllabus Objectives

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

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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.