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Document cover page: parts per thousand
Parts Per Thousand
Source: Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education, University of Hawai'i
[03-Jan-2019] Concentration is a measure of the relative amount of dissolved substances in a solution. There are many elements dissolved in seawater and different amounts of each element, which means that each element has a different concentration. Concentration can be expressed in many different ways. Sometimes concentrations are expressed in terms of a particular compound. Other times, concentrations are expressed in terms of individual elements, regardless of the compounds in which they are found. In aquatic science, concentration is most often expressed in terms of the number of grams (g) of an element dissolved in 1,000 g of seawater. The unit for this measure of expressing concentration is parts per thousand, or ppt. For example, salinity is the measure of the number of grams of salts per kilogram (kg) of seawater. The average salinity of seawater is about 35 g/kg of seawater, or 35 ppt. In this activity, students breakdown the constituents of sea water (hydrogen, oxygen, major elements, minor elements and trace elements) into parts per thousand.

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