Physical Properties
* Definition: Characteristics of a substance that can be observed or measured without changing the substance's chemical composition.
* Examples: Color, density, melting point, boiling point, hardness, state of matter (solid, liquid, gas).
Melting is a physical change because:
* No new substances are formed: When wax melts, it simply changes from a solid to a liquid. The chemical composition of the wax remains the same. It's just a change in the arrangement of the molecules.
* Reversible: The melted wax can be solidified again by cooling it down, restoring its original state.
Chemical Properties
* Definition: Characteristics of a substance that describe how it reacts with other substances or how it behaves under certain conditions, leading to a change in chemical composition.
* Examples: Flammability, reactivity with acids, oxidation (rusting), decomposition.
Flammability is a chemical change because:
* New substances are formed: When wax burns (a combustion reaction), it reacts with oxygen in the air. This reaction produces carbon dioxide, water vapor, and other products. The original wax molecules are transformed into new molecules.
* Irreversible: The burning process cannot be easily reversed to get back the original wax.
In summary: Melting changes the *state of matter* of the wax but doesn't alter its chemical makeup. Flammability involves a *chemical reaction* that creates entirely new substances.
