Mixtures and Separations

• Classifying Matter

  A) Pure substances

  B) Mixtures

  C) Compound

  D) Element

  E) Homogeneous Mixture

  F) Heterogeneous Mixture

  
• Matter can be placed into two main groups: pure substances and mixtures.
• Pure substance is composed of only one type of material. Additionally, it cannot be separated or purified from other kinds of substances by physical means.

  
• Properties of pure substances:

  • Defined boiling, melting and freezing point
  • Defined density
  • Fixed composition
• Pure substances can be further classified into elements and compounds.

  
• Elements are the simplest form of matter that cannot be broken down chemically to produce simpler substances.

  
• Compounds are substances that are made up of two or more elements chemically combined.

  
• Mixtures are composed of two or more substances that are not chemically combined, therefore they can be separated by physical means.

  
• Mixtures can be further classified into homogenous mixtures and heterogeneous mixtures.
• Homogenous mixtures are those in which the properties and composition are the same. They are also known as solutions. They do not settle undisturbed and cannot be separated by filtering. Example: a cup of tea and salt + water mix.

  
• Heterogenous mixtures are those in which the components have different properties and compositions. This includes suspensions and colloids. Examples include sand + water, mayonnaise

  
• A solvent is a liquid that can dissolve a substance, while a solute is a dissolved substance.

  
• Suspensions are heterogeneous mixtures containing particles that are not uniform and visible to the naked eye. If left undisturbed, the particles in a suspension will eventually settle and the components can be filtered.

  
• Colloids are heterogeneous mixtures with very small particles that are too large to pass through a membrane but too small to see without magnification. Colloids do not settle when left undisturbed. Example: blood plasma, smoke, mayonnaise

  
• The Tyndall effect is the scattering of visible light by particles in a colloid. When light is passed through a true solution, the dissolved particles are too small to deflect the light. However, the dispersed particles of a colloid, being larger, do deflect light.

  
• Mixtures:

  A) Solution

  B) Colloid

  C) Suspensions