Understanding Pure Substances, Mixtures, and Separation Methods

Pure Substances and Mixtures

Pure substance: Each type has a defined composition and specific properties and invariant features.

Examples: Distilled water, pure gold, oxygen, table salt.

Mixture: Consists of two or more substances in varying proportions.

Examples: Milk, tap water, air.

Types of Mixtures

Heterogeneous mixtures: Components can be distinguished with the naked eye or with optical instruments.

Examples: Granite, water and oil.

Homogeneous mixtures (Blended): The components cannot be distinguished because the particles are completely mixed.

Examples: Sea water, bronze.

Colloidal Dispersions: To distinguish the components, you need to use microscopes. The set of all colloids consists of a dispersed phase and a substance called the dispersing medium.

Identification of Pure Substances

These are typical properties of a substance that allow for its identification.

Examples: Density, melting point, boiling temperature, color, odor.

Density, Melting, and Boiling Points

These are characteristic properties of each substance, representing concrete values for each pure substance. If a substance does not maintain the same density or boiling temperature while changing state, it is a mixture of different substances.

Solutions and Solubility

Solutions: A solution is a homogeneous mixture of substances. The component present in a lesser amount is called the solute, and the component comprising the majority is the solvent.

Solubility: The maximum amount of solute that dissolves in a solvent at a certain temperature. When a solution no longer supports the addition of more solute, it is said to be saturated. When a substance does not dissolve, it is insoluble, and liquids that do not mix are immiscible.

Concentration of a Solution

The amount of solute dissolved in a quantity of solution or solvent.

Percentage mass/volume:

Separation Techniques

These are procedures for separating the components of a mixture:

• Decanting: Used to separate heterogeneous mixtures.
• Filtration: Retains solids not dissolved in liquids through a filter.
• Vaporization: The solution is heated in a porcelain capsule to evaporate the solvent.
• Crystallization: The solution is left in a crystallizer so the solvent evaporates at room temperature, allowing the solute to form crystals.
• Other techniques: Extraction, sublimation, and magnetism.

Distillation and Chromatography

Distillation: Allows for the separation of homogeneous liquid mixtures by boiling them at their respective temperatures. A mixture of gases can also be separated by distillation by condensing them.

Chromatography: Consists of separating substances by dragging them with a solvent, where each moves at a different speed.