Mixing and Dissolving

Students explore homogeneous and heterogeneous mixtures, solutes and solvents.

Introduction

In this lesson we will be exploring how particles interact with each, specifically the different types of mixtures. A mixture is created when two or more different substances which are physically combined.

Classification of Matter

Types of Mixtures

  • Homogeneous Mixtures
    • A mixture that looks as though the original substances have evenly combined throughout the entire mixture. A homogeneous mixture that has no “left-over” substances or settling is referred to as a solution. An example of a homogeneous mixture is paint.
  • Heterogenous Mixtures
    • A mixture that has its original substances still identifiable, these types of mixtures are often called mechanical mixtures. An example of a homogeneous mixture is sand.
  • In-Between Mixtures
    • Suspension
      • A heterogeneous mixture where the particles settle. These particles are large enough to be trapped by filters in a process called sedimentation.
    • Colloid
      • A heterogeneous mixture where microscopic particles do not settle, but are small enough to pass through filters. Often holding up a light to the mixture will reveal these particles. By using an emulsifying agent the particles can remain dispersed in the mixture even longer, this is referred to as emulsion.

Solutes and Solvents

When two substances are mixed together they may form a solution by dissolving one substance in the other. This is possible because some substances are soluble in other substances. A good example of this is when sugar dissolves in water, sugar is water-soluble.

  • Solvent
    • A solvent is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Source
  • Solute
    • A solute is a substance dissolved in another substance, known as a solvent. Source

Water is often called the “universal solvent” because it can dissolve so many substances.

Solubility

Solubility is the mass of a solute that can dissolve in a specific amount of a solvent at a given temperature. The solubility of substance is measured in grams per 100 mL of the solvent (note: that 1mL of water is equal to 1 gram of water).

  • Saturated Solutions
    • A saturated solution is a solution that no more solute can be dissolved into it at a given temperature.
  • Unsaturated Solutions
    • An unsaturated solution is a solution where more solute can be dissolved into it at a given temperature.
  • Supersaturated Solutions
    • A supersaturated solution contains more solute than can normally be dissolved in the solvent at a given temperature. This can be done by heating the solvent and mixing the solute into the solution until it is completely saturated. Let the solution cool without irritating it, eventually the excess solute will solidify as the solution cools.
  • Insoluble Substances
    • Some substances cannot be dissolved in a particular solvent, these substances are referred to as insoluble in the given solvent.

Workplace Hazardous Materials Information System

The Workplace Hazardous Materials Information System or WHMIS is a system using symbols, procedures, and information about a given substance to ensure its safe use in the classroom, at home, and in the workplace.

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