Understanding Matter: Systems, Mixtures, Solutions

Matter and Material Systems

Matter and Its Appearance.

Heterogeneous Material Systems

Heterogeneous material systems are those that have different properties in different parts of the system. Distinct parts can be distinguished either by the naked eye or microscopically.

Separating Heterogeneous Mixtures

A heterogeneous material system formed by various substances is called a heterogeneous mixture. To separate heterogeneous mixtures, various techniques are used:

• Components with Different States of Aggregation

  To separate heterogeneous mixtures where, for example, one component is a solid and the other a liquid, filtration can be used.

• Components with Different Density

  In this case, techniques such as sedimentation, decantation, or centrifugation are used:

  • Sedimentation: The separation, by the action of gravity, of the components of a mixture with different densities.
  • Decantation: Allows separating immiscible liquids, such as water and oil, using a funnel.
  • Centrifugation: Artificially increases the rate of separation of mixture components that have different densities by means of rotation.

• Components with Different Solubility

  They can be separated by selective dissolution.

Homogeneous Material Systems

Homogeneous material systems are those that have the same composition and properties throughout any portion thereof. Distinct parts cannot be distinguished even with a microscope.

Solutions and Pure Substances

A homogeneous material system consisting of a mixture of 2 or more components is called a solution or homogeneous mixture.

A homogeneous material formed by a single component is called a pure substance. Pure substances have determined melting and boiling temperatures. The values of these properties for mixtures are not fixed; they are, however, variable and depend on the composition.

Concentration of Solutions

Concentration of a solution is expressed numerically as the ratio of a quantity of solute to a quantity of solution. Solutions can be described by their concentration:

• Diluted: If the amount of solute compared to solvent is very small.
• Concentrated: If the amount of solute to solvent ratio is high.
• Saturated: If the solute is in the maximum proportion possible.

Solubility

This is the maximum amount of solute that can dissolve in a certain amount of solvent at a given temperature.

• Solubility of a solid in water generally increases with increasing temperature.
• Solubility of gases in water, for a given pressure, decreases with increasing temperature.

Elements and Compounds

Compound: A pure substance that by transformations can become more simple. No other substances are composed of it.

Element: A pure substance that cannot be decomposed into other more simple substances is called an element.