SCSC 301 Midterm: Exam 3 Review
24 Feb 2017
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Document Summary
Organic and inorganic matter with very small particle size (clay-sized) and a correspondently large surface area per unit of mass. Size too small to observe with a light microscope. Starts at <0. 002 mm or 2 microns. Can be observed with an electron microscope. Inorganic colloids are the main elements in silicate clays. High surface area: as particle size decreases, the surface area increases. Have a surface charge: may be negative or positive. In most soils we grow plants in it will be a negative charge. Absorb cations and water: absorb opposite sign, to give us a neutral charge, adhesion. Surface area large surface area per unit of mass. Some have internal surfaces in addition to external surfaces. Surface area of colloids is at least 1000 times that of coarse sand. Common values of colloid surface area from 10 m2/g to 800m2/g. 800 m2/g is the smallest we can have.
