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Lesson 8 - Mixtures

Student Performance Objectives
1. Define solvent and solute.
2. Define the following terms and give an example related to the human body: true solution,
    suspension, colloidal dispersion, and emulsion.

Lesson Outline
A. Concepts of solvent and solute. Importance of particle size and hydrophilicity.
B. True solutions and examples from the human body. Particles making up a true solution are
     so small that they resist the pull of gravity and will never settle out of the solution, unless
     the solvent evaporates.
        1. The body's ions (electrolytes) are in true solution in the body water.
        2. Blood sugar (glucose) is in true solution in the plasma.
C. Suspensions and examples from the human body. Particles making up a suspension are
     large enough to be affected by gravity and will settle out on standing for a time - like sand
     settling out in a pail of water.
        1. The erythrocytes (red blood cells, RBC's) are suspended in the plasma.
        2. The leucocytes (white blood cells, WBC's) are suspended in plasma and lymph.
D. Colloidal dispersions and examples from the human body. Particles making up a suspension
     are small enough not to settle out of solution on standing, but large enough to be visible in
     some way to the human senses - like the proteins in milk or the egg protein in egg-drop soup.
        1. The proteins (e.g., albumin, globulins) of plasma are in a colloidal dispersion.
        2. The glycoproteins in the intercellular spaces in tissues are colloidally dispersed.
E. Emulsions - two liquids suspended in each other.
        1. During digestive processes in the human small intestine, the mixture of bile salts, from
            the liver and gall bladder, mixing with dietary fat, forms an emulsion of the fatty
            molecules with the water of intestinal fluid.
F. DEMONSTRATION: Point is to see the various types of mixtures. Mix salt and water and
    watch the crystals disappear; mix sand and water and the particles only remain suspended
    when the mixture is swirled; observe milk under a microscope and observe the colloidally
    dispersed lipoprotein particles; mix oil and water to observe their lack of mixing and then
    add a pinch of bile powder and observe emulsion formation.

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