Physical Properties in Chemistry: Definitions and Examples

Physical Properties

Definition and Overview

Physical properties are measurable characteristics that describe the state of a chemical compound without altering its chemical identity. These properties can be observed or measured without changing the chemical structure of a substance.

• Physical properties are typically detected through the senses or simple measurements.

• They help in identifying and classifying substances in chemistry.

Common Physical Properties

• Color: The visual appearance of a substance, such as white, red, or blue.

• Density: The mass per unit volume of a substance. $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Mass: The amount of matter in a substance, measured in grams or kilograms.

• Volume: The amount of space a substance occupies, measured in liters or cubic centimeters.

• Hardness: The resistance of a substance to being scratched or indented.

Examples of Physical Properties

• Mercury is a silvery liquid at 25°C: This describes the state and appearance of mercury without changing its chemical composition.

• The density of gold is 7.87 g/cm³: This is a measurable property that does not involve a chemical change.

• An iron bar rusts: Not a physical property; this is a chemical change.

• Platinum glows when heated: This describes a physical response to temperature.

• Gallium is a silver-colored metal: This describes the color and appearance.

Distinguishing Physical and Chemical Properties

Physical properties do not involve the formation of new substances, while chemical properties describe a substance's ability to undergo chemical changes.

Physical Property	Chemical Property
Color	Reactivity with water
Density	Flammability
Mass	Ability to rust
Volume	Combustion
Hardness	Acidity

Practice Questions

• Which of the following is not a physical property?

  • a) The brittleness of solid sulfur. (Physical property)

  • b) The density of iron is 7.87 g/cm³. (Physical property)

  • c) Platinum glows when heated. (Physical property)

  • d) Gallium is a silver-colored metal. (Physical property)

  • e) An iron bar rusts. (Chemical property)

Additional info: Physical properties are essential for identifying substances and distinguishing them from chemical properties, which involve changes in chemical composition.