Observable Changes:

* Change in state of matter: Melting, freezing, boiling, condensation, sublimation, and deposition all involve changes in the physical state of a substance, but not its chemical composition.

* Change in shape or form: Bending, cutting, crushing, or molding a material changes its shape but not its chemical makeup.

* Change in size: Expanding, contracting, or dissolving a substance alters its size but not its chemical identity.

* Change in color: Some physical changes, like mixing colored liquids, can result in a new color but don't indicate a new substance.

* Change in texture: Grinding, crushing, or pulverizing a substance can alter its texture without changing its composition.

Key Points:

* No new substances are formed: The fundamental chemical makeup of the substance remains the same.

* Changes are usually reversible: The original substance can be recovered through physical means.

* No energy changes are significant: While some energy changes may occur, they are usually small and do not indicate a chemical reaction.

Examples:

* Melting ice: Ice (water in a solid state) melts into liquid water, but the chemical formula (H₂O) stays the same.

* Cutting paper: The paper is divided into smaller pieces, but the chemical composition of the paper remains unchanged.

* Dissolving sugar in water: The sugar disappears, but it is still present in the water as sugar molecules, not a new substance.

* Boiling water: Liquid water becomes steam, but it's still H₂O.

It's important to remember: Some physical changes can be difficult to distinguish from chemical changes. For example, burning wood appears to be a physical change (wood changing to ash), but it's actually a chemical change due to the formation of new substances (ash, smoke, gases).