2.2 Properties of Matter

Key Concepts

1. Physical Properties

Physical properties are characteristics that can be observed or measured without changing the substance's identity. These include color, odor, density, melting point, boiling point, and hardness.

Example: The color of a copper wire is a physical property, as it can be observed without altering the copper's composition.

2. Chemical Properties

Chemical properties describe how a substance can change or react to form new substances. These include flammability, reactivity with acids, and the ability to oxidize.

Example: The ability of iron to rust when exposed to oxygen and moisture is a chemical property, as it results in the formation of a new substance, iron oxide.

3. Extensive Properties

Extensive properties depend on the amount of matter present. These include mass and volume. Changing the amount of substance changes these properties.

Example: Doubling the amount of water in a container doubles both its mass and volume.

4. Intensive Properties

Intensive properties do not depend on the amount of matter present. These include density, temperature, and melting point. These properties remain constant regardless of the quantity of substance.

Example: The density of water is 1 g/cm³, regardless of whether you have 1 liter or 10 liters of water.

Examples and Analogies

Example: Physical and Chemical Properties of Wood

Wood has physical properties such as color (brown), texture (rough), and density. Its chemical properties include the ability to burn (flammability) and react with oxygen to form carbon dioxide and water.

Analogy: Physical Properties as Outer Appearance

Think of physical properties as the outer appearance of a person. Just as you can describe someone by their height, hair color, and eye color without changing who they are, you can describe a substance by its physical properties without altering its identity.

Example: Extensive and Intensive Properties of a Metal Bar

A metal bar has extensive properties such as mass and volume, which increase if you add more metal. Its intensive properties, such as density and melting point, remain the same regardless of the bar's size.

Analogy: Intensive Properties as Universal Traits

Think of intensive properties as universal traits. Just as all humans have a normal body temperature of 98.6°F, all samples of a specific substance have the same intensive properties.