Why is the sea salty?
Grade Level: K-3

Overview In preparing for an ocean unit, do a 'K W L' organizer. 'K' is for what we know about the ocean. 'W' is for what we want to learn about the ocean. 'L' is for what we have learned about the ocean. The following lesson was developed because the students wanted to know why the ocean is salty.

Purpose For students to observe how salt concentration increases in water. Also, how the salt remains after the water evaporates.

Objectives Students will be able to:
i. Demonstrate that salt can make water salty.

ii. Explain why the sea is salty.

Resources/Materials

Rock salt, water, containers, strainers.

Activities and Procedures
i. Make the children pour water over the rock salt which is contained in a strainer. The water plus dissolved salt will be collected in a plastic cup. Students will taste the water sample.
ii. Heat the salty water and allow the water to evaporate. Observe that the salt remains.

iii. The above procedure is repeated over a 3 or 4 day period. The students will observe that the salt increases each time new salt water is added.

Tying it all together

Students will do a Saltwater Painting to once again observe the evaporation process. Mix warm water, salt, and food coloring. Paint pictures with the mixture on white paper. Let it dry. The water evaporates, but the salt remains, creating beautiful pictures.

Assessment

What do the children think is the difference between: River water and sea water?

Suggestions/Modifications

  • Students may trace the origins of the table salt that is used in food, i.e. what is the process that brings the salt from the earth to the table.
  • Students may try to discover why the salt will stay in the water and not separate from it without heat.
  • Students may explore all of the different ways salt is used.
Author(s) Pam Hansen and Christy Bingham Cleveland Elementary School, Cleveland, UT
http://www.col-ed.org/cur/