1.3 properties of matter

Properties of Matter

  • Familiar properties of materials include:

    • Hardness of steel

    • Flexibility of rubber

    • Glow of a wood fire

Classification of Properties

  • Properties of matter can be classified into two types: physical or chemical.

  • Understanding these classifications is essential for distinguishing between physical and chemical changes.

Physical Properties

  • Can be observed without altering the substance's identity and composition.

  • Examples include:

    • Color

    • Odor

    • Density

    • Melting point

    • Boiling point

    • Hardness

  • Intensive Properties:

    • Characteristics that do not depend on sample size (e.g., density, boiling point).

    • Useful for identifying substances.

  • Extensive Properties:

    • Characteristics that depend on the amount of substance (e.g., mass, volume).

Chemical Properties

  • Describe how a substance might change or react to form new substances.

  • Common example:

    • Flammability: Ability of a substance to burn in oxygen.

Changes in Substances

  • Two categories of changes that substances undergo: physical or chemical.

Physical Changes

  • Involves a change in physical appearance without altering composition.

  • Example: Evaporation of water:

    • Water transitions from liquid to gas but maintains its chemical structure (H2O).

  • Changes of state (e.g., liquid to gas, liquid to solid) are physical changes.

Chemical Changes

  • Also referred to as chemical reactions.

  • A substance transforms into a different substance with a different chemical identity.

  • Example: Burning of hydrogen:

    • When hydrogen reacts with oxygen, it forms water (H2O).

  • Chemical reactions can involve dramatic transformations.

Separation of Mixtures

  • Mixtures can be separated based on differences in their properties.

  • Heterogeneous mixtures, such as iron and gold filings, can be sorted by:

    • Color (manual sorting)

    • Magnetism: Using a magnet to attract iron filings, leaving gold behind.

  • Chemical Differences:

    • Acids dissolve iron but not gold.

    • By placing a mixture in acid, iron can be dissolved, allowing for separation.

Methods of Separation

  • Filtration: Separates components based on solubility.

  • Example: Dissolving iron with acid leaves gold behind.

  • Distillation: Utilizes differing abilities of substances to form gases.

    • Example: Boiling saltwater leaves salt behind while water evaporates.

    • Vaporized water can condense back into liquid form.

  • Chromatography:

    • Separation based on substances' adherence to surfaces of solids.

    • Provides a visual method for separating components.