ELECTROLYSIS OF SALT WATER
Unit: Salinity Patterns & the Water Cycle l Grade Level: High school l Time Required: Two 45 min.
periods l Content Standard: NSES Physical Science, properties and changes of properties in matter;
atoms have measurable properties such as electrical charge. l Ocean Literacy Principle 1e: Most of
of Earth's water (97%) is in the ocean. Seawater has unique properties: it is saline, its freezing point is
slightly lower than fresh water, its density is slightly higher, its electrical conductivity is much higher, and
it is slightly basic.
Big Idea: Water is comprised of two elements – hydrogen (H) and oxygen (O). Distilled water is pure
and free of salts; thus it is a very poor conductor of electricity. By adding ordinary table salt (NaCl) to
distilled water, it becomes an electrolyte solution, able to conduct electricity.
Key Concepts
o
Ionic compounds such as salt water, conduct electricity when they dissolve in water.
o
Ionic compounds consist of two or more ions that are held together by electrical attraction. One of
the ions has a positive charge (called a "cation") and the other has a negative charge ("anion").
o Molecular compounds, such as water, are made of individual molecules that are bound together by
shared electrons (i.e., covalent bonds).
o
Essential Questions
o What happens to salt when it is dissolved in water?
o What are electrolytes?
o How can we determine the volume of dissolved ions in a water sample?
o How are atoms held together in an element?
Knowledge and Skills
o Conduct an experiment to see that water can be split into its constituent ions through the process of
electrolysis.
o Prepare and experiment with a 10% salt solution to better understand the process of ion exchange.
o Discuss and research the "softness" and "hardness" of water.
o Use the periodic table to identify elements and learn their characteristics.
Prior Knowledge
o Define the difference between ionic and molecular compounds.
o Salt consists of sodi