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E.T.- A LOCAL WAY OF LEARNING


Title: SALT OF THE EARTH

Author: Leslie Repp
Eulalie R. Rivera Elementary School

Grade Level: 4

Concepts: Disciplines:
1. The Sun 1. Science
4. Clean Water 2. Social Studies
6. Natural Resources 3. Mathematics

Objective:
Students shall demonstrate, by weighing and recording, the daily loss of sea
water to evaporation over a period of a week and that remains are cube shaped
salt crystals in the residue.

Rationale:
Collecting salt by evaporation has been practiced in many lands bordering the
seas for centuries. Salt was used to preserve food before the widespread use of
refrigeration. Like the Ancient Mariner of Colridge, we live surrounded by water
in the islands, but we frequently are in dire need of fresh water. People,
animals and most plants can not live on salt water intake. Trapping the
evaporating water provides drinking water, i.e., distillation or the
desalination process.

Materials Needed:
Shallow container (aluminum pie or cake pan) for salt water, scale, microscope
or hand lens.

Directions:
Ask a student to bring sea water in a quart plastic container to class. Place
the water in a shallow container such as in an aluminum pie or cake pan provided
by
bakeries. Use a scale to record the initial weight of the water and container.
Place the pan with the water by a window or area exposed to sunlight, keeping it
in the same area until all the water has evaporated. Each day, record the weight
of the water and container and determine how much evaporation took place. When
all the water has evaporated, examine the salt crystal that remain and compare
the taste to mineral salt. Note: Note additional activities on work sheet.

Evaluation:
What is evaporation? What causes it? What is left when sea water has evaporated?
If you trap the evaporated water, could you make fresh water?












Activity Record:
E.T.
SALT OF THE EARTH

1. Date experiment began:

2. Weight of sea water and container:


Name


3. Daily evaporation record:


Weight of Water
and Container


Amount
Evaporated


Weather
Conditions


a. Day 1

b. Day 2

c. Day 3

d. Day 4

e. Day 5


4. Date all water evaporated?

5. a. What remained in the bottom of the pan?

b. What is the weight of the residue?

c. What was the proportion of the weight of the residue to the original
weight of the sea water?




A comparative experiment could be done by placing another sea water container,
similar in weight, in a place not exposed to sunlight and record the length of
evaporation time. This would demonstrate the evaporative power of the sun.


1. Larger container
with salt water


2. Float a smaller empty
.- aluminum pan in the larger
container

3. Cover over both containers
with clear plastic (Saran
Wrap)

4. Place in sunlight