Grade:
Time:
Topic:
Concept:
SOL: 5.6
The student will investigate and understand characteristics of
the ocean environment. Key concepts include
-
geological characteristics (continental shelf,
slope, rise);
-
physical characteristics (depth, salinity, major
currents);
-
biological characteristics (ecosystems); and
-
public policy decisions related to the ocean
environment (assessment of marine organism populations,
pollution prevention).
Rationale:
Goals:
Cognitive Objectives: The student will orally explain the desalination process
with 100% accuracy. The
student will be able to answer 3 out of 4 questions about the desalination
process and its application.
Psychomotor
Objective: The student
will create a small solar powered still, exercising
fine motor skills and coordination.
Affective
Objective: The student will understand that desalination is important
to parts of the world that do not have rich water reserves.
Content:
Virginia SOL 5.6
Characteristics of water
Properties of solutions
Early understanding of molecules
Application of desalination on the world scale
The student will understand how a solar still works and
will be able to apply its use by making a small model. The student will understand that although saltwater is a
solution, the solution can be separated quite easily by using the sun’s
energy. The student will orally
state the implications solar stills have on the world and will orally suggest
how a solar still works.
Materials:
|
pebbles
|
tablespoon measure
|
rubber bands
|
|
Saran Wrap (plain)
|
clear plastic cups
|
black construction paper
|
|
tablespoons salt
|
small plastic cups
|
|
Procedure:
The student will follow the teacher’s directions and
create a small solar still. After
the still has been completed, the teacher will bring out a solar still that has
already been in sunlight for one or two days.
The teacher will ask,
“Who would like to taste the water that is in my small
plastic cup?”
The child will taste it.
After the child tastes the water, the teacher will ask,
“Does the water taste salty?”
Probably not.
The teacher will ask the class,
“What do you think happened in this solar still that made
water end up in my small cup? And
why doesn’t the water taste salty?”
The students will offer suggestions, and the teacher will
write all of them on the board.
As the children make sense of the experiment, the
teacher will explain more about their correct inferences and give more
information about the properties of the saltwater solution. The saltwater is a solution, so the salt molecules are
binding with the water molecules and forming a completely new substance.
This means that the salt and water are connected in a way that cannot be
broken by filter paper, whose holes are too large to separate the salt from the
water.
The sun provides heat energy that is strong enough to
break the bonds between the water and salt, however, and the sun continues to
power the evaporation of the water. When
the water evaporates as high as the saran wrap, it condenses.
We wanted to collect the desalinated water in a cup, so we placed a
pebble in the middle so that the water would slide down the saran wrap and land
in our cup.
“Now, who can tell me why we would place black paper
underneath our solar still?”
(Black absorbs light,
white reflects it; so the fresh water will be collected faster if black is
underneath the still)
Are solar stills like
the ones we made useful for anything? Where
might they be useful? As the
children offer ideas, the teacher records their responses on the board.
When the children are finished, the teacher will show them a solar still
website and talk about the place (near the desert) where this solar still is
being tested.
Closure:
One student will be
asked to put everything away (desks, materials) that the class moved and the
teacher will ask everyone else to put away their things.