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Activity: Parts Per Thousand

NGSS Science and Engineering Practices:

NGSS Crosscutting Concepts:

NGSS Disciplinary Core Ideas:


  • Table 2.5
  • Fig. 2.20
  • Colored pencils



The 1,000 squares in Fig. 2.20 represent 1,000 g of seawater. The table is 40 by 25 squares. Each square represents 1 g.
  1. Devise a way to color-code each of the following categories of seawater. Make a key at the bottom of Fig. 2.20 to explain your color code.
    1. Water elements (H and O)
    2. Major elements
    3. Minor elements
    4. Trace elements.
  2. Use Table 2.5 to determine the total number of grams of each of the following categories of elements in 1,000 g of seawater. Color the number of squares corresponding to this concentration in Fig. 2.20.
    1. Water elements (H and O)
    2. Major elements
    3. Minor elements
    4. Trace elements
  3. Compare your completed Fig. 2.20 to your classmates’.


Activity Questions: 
  1. How did you choose to color-code your table? Why did you choose these colors?
  2. When comparing your data to that of other students, did your color-coding system matter?
  3. Use as many matter terms as you can to describe seawater (e.g. solid, liquid, gas, element, compound, mixture, solution, solvent, solute, concentration).
  4. Why are hydrogen (H) and oxygen (O) given their own category as elements in seawater?
  5. The average concentration of sodium chloride (NaCl) in seawater is 35 ppt. State this same concentration in parts per hundred (percent or %).
  6. Why do you think marine scientists use parts per thousand (ppt or ‰) rather than parts per hundred (percent or %) to express concentrations of dissolved materials in seawater?

Table of Contents:

Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.