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The DLMindex links to select collections of K-12 digital learning materials developed by UC Berkeley Interactive University Projects over the past five years. Each item contains descriptive metadata about the resource. Users can browse the index or use an early search prototype.
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ES: Water Quality - TDS
Title: Water Quality - Total Dissolved Solids
Location: http://urbanwatershed.org/modules/TDS/tds.htm
Project: Environmental Science
Creator:
Subject area: Science
Grade level: 11, 12
Purpose: Dissolved solids, such as minerals, salts, metals, cations or anions, have a significant effect on water quality. Water hardness, a measure of the cations dissolved in water, has both environmental and domestic implications. Dissolved heavy metals (such as arsenic, cadmium, iron, lead, and mercury) are often toxic to plants and animals, including people, even at low concentrations. More common dissolved solids (including sodium, potassium, sulfates, chloride, nitrate and fluoride) can have both beneficial and detrimental environmental effects.
Standards:
Type: Text
Duration:
Student Objectives: Students can determine the Total Dissolved Solids (TDS) in a sample in two ways: roughly, by measuring electrical conductivity; and precisely, by weighing the residue left behind after evaporation. Students should be familiar with the different filter and purification processes that drinking/domestic water goes through, and have an understanding of hard water, the sources of heavy metals in water, and at what levels specific dissolved solids become toxic.
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