Physical and Chemical Change Study Guide

Physical Change

  • Definition: A change in the shape or appearance of a substance where no new chemical products are created.

  • Key Characteristics:

    • The substance consists of the same particles before and after the change.

    • Only the energy of the particles changes.

    • Physical changes are reversible/replaceable.

  • Occurrences:

    • When a force is applied.

    • When substances are cut, broken into smaller pieces, or mixed together.

    • Changes in state: All state changes are physical.

  • State Change Terms:

    • Sublimation: Solid to gas.

    • Deposition: Gas to solid.

Chemical Change

  • Definition: A change that produces entirely new substances with different chemical compositions and properties.

  • Key Characteristics:

    • New products are formed.

    • Chemical changes are not reversible.

  • Indicators of Chemical Change:

    • Change in temperature.

    • Change in colour.

    • Production of light.

    • Release of gas (bubbling, smoking, or noticeable smells).

  • Examples:

    • Burning firewood: Wood $\rightarrow$ Ash.

    • Rusting Iron: Iron + oxygen + water = iron oxide (rust)\text{Iron + oxygen + water = iron oxide (rust)}.

Comparison of Changes

  • New Substance:

    • Physical: No.

    • Chemical: Yes.

  • Reversible:

    • Physical: Yes.

    • Chemical: No.