Seashore Science
Wherever you live, your class
can explore the sand and the sea with our "sun-sational"
theme unit
By Mackie Rhodes
Wade into science learning with our sand and sea activities.
Start by making your own safe (and salty!) seawater with this
quick and easy recipe: Add 1/4 cup of salt for every 1 cup
of hot water. Stir with a large wooden spoon, and then let
the water cool.
The Salty Sea
Although oceans cover almost three-fourths of the earth
and support an abundance of life forms, the water in the
ocean is not fit for human consumption. To help the class
discover why, give each student a small cup of seawater
and a craft stick. Invite children to dip their craft sticks
into the water and then taste it. What common flavor is
in the water? Explain that seawater is unsuitable for drinking
because of its high salt content.
SEASHORE FACT: Most of the salt in seawater is the same
as common table salt. Too much salt intake can cause dehydration.
Water Weigh-in
Based on their first experiments, the children
have discovered that seawater contains salt. But how does
the salt content affect the weight of seawater? To find
out, have children pour fresh water into one container and
an equal amount of seawater into a separate, identical container.
Ask them to weigh each container (or place the two containers
on a balance). How do the weights compare? Help the children
make hypotheses and conclusions.
SEASHORE FACT: The salt in seawater makes it heavier,
or denser, than freshwater.
Dry Sand, Wet Sand
Waves are the primary means for sand to travel
from the sea to shore and back out to sea again. Using only
a clear plastic container filled with dry sand, help children
discover how the sand and the sea interact.
1. Have the children tilt the tray back and forth. Observe
what happens. Then add water until the sand is just damp
enough to pack. Now tilt the tray. Unlike the dry sand,
the wet sand remains in place. What happens when a seashell
or the end of a straw is pressed into the sand?
SEASHORE FACT: Individual grains of dry sand do not
stick together. But when sand is wet, water surrounds
each grain and creates surface tension, which causes the
grains to cling to each other. This is why it is possible
to build a sandcastle.
2. Saturate the sand with more water until it becomes
soft and mushy. Tilt the tray and observe what happens to
the now saturated sand. Then have the children try to make
a seashell impression in the sand. The sand will not hold
the shape of the impression. Why?
SEASHORE FACT: When sand becomes saturated with water,
the individual grains separate so that the sand cannot
be packed or even hold a shape.
Grain-by-Grain Erosion
Sand is a small particle of rock — a result of erosion
over many years. Although tiny, grains of sand can also
be the cause of erosion. To understand how, have children
isolate a grain of sand and then rub it over a piece of
foil with their fingertips. What happens? Explain that,
just as the sand "cuts" into the surface of the foil, it
can also cut into (or erode) the surfaces of surrounding
structures.
SEASHORE FACT: Along the seashore, houses and docks
can be eroded by the tiny, hard granules of sand that
are washed or blown against them.
Seashore Sensory Surprises
Sand from the seashore is full of surprises. To help children
discover some of these surprises, put a different seashore
item (such as a starfish, a seahorse, a conch shell, a sponge,
or driftwood) in separate pillowcases. Label each one with
a number. Then have the children take turns reaching into
the pillowcase to feel each item. Ask them to write a short
description of the item on a note card and guess what it
is. Then read the descriptions for each mystery object,
removing the object from the pillowcase to show to the children.
Afterwards, the children can add information to their descriptions
based on what they learned from observing the objects.
Crystal Creations
Ocean water is replenished by the water cycle.
But what happens to the salt in seawater during this process?
Pose this question to students. Then provide them with sheets
of foil, eyedroppers, and containers of seawater colored
with food coloring. Invite children to use the droppers
to make colorful designs on the foil. Set their creations
in the sun to dry. As the water evaporates, salt crystals
are left on the foil.
SEASHORE FACT: As saltwater evaporates, it leaves the
salt behind. At the beach, salt residue can be seen on
the surface of cars, windows, and even on our skin.
Wave Explorations
Floating objects on or beneath the sea's surface
are moved about by waves. You can explore the science of
waves using a large aquarium tank (or a long, clear plastic
storage container, such as the 66-quart size). Use a wipe-off
pen to mark inch-wide increments from top to bottom along
the side of the tank. Place the tank on a sheet of plastic
and fill it two-thirds full with water. Then mark the water
line. Ask students to record their observations in a journal
as they do the following experiments:
1. From one end of the tank, have the children blow air
gently across the surface of the water. What happens? Repeat
several times, asking them to blow with more force each
time.
2. Float an empty film canister in the middle of the tank.
Have children create gentle waves at one end. What happens
to the canister?
3. Use a flat paddle to create waves at one end of the
tank. With the water line as a reference point, record the
height of each wave's crest (top) and the depth of its trough
(dip). For each wave, the two should be about the same distance
above/below the water line.
SEASHORE FACT: The speed of the wind usually determines
the power of a wave: the more wind speed, the bigger the
wave. Floating objects remain in almost the same place after
a wave passes through.
Buoyancy Boat
Ask students to speculate on whether or not the
density of seawater will affect an object's buoyancy (its
ability to float). Invite them to make a buoyancy boat to
test their ideas. To make one, use a permanent marker to
mark 1/8" increments along the side of a plastic applesauce
cup, or similar container. Then press play dough into the
bottom of the cup, distributing it so that the cup sits
level when placed in water. (Add a sandwich pick flag, if
you like.) First float the cup in a container of freshwater.
Record the level of the water to see how much water is displaced
by the boat. Repeat the procedure using seawater. Have students
compare and discuss their observations.
SEASHORE FACT: The salt in the denser seawater pushes
up against an object, making it more buoyant (able to
float higher) than in freshwater.
Shell Notebooks Reproducible
What do fish and other ocean creatures eat? Explore
the food chain of the sea with students. Then invite them
to create booklets to demonstrate their knowledge. To begin,
have children cut out the Conch Shell Reproducible
and cut along the thicker dotted lines. Ask children to
glue the outer part of the shell to a sheet of blue construction
paper. Then give each child a stack of five sheets of blank
paper to staple inside the shell (as shown) to create pages.
Have students describe and illustrate a different step of
the food chain on each page. Finally, have the children
decorate their shell books with colors and craft items of
their choice.
The Creatures in the Sea
Not all sea creatures are fish! Brainstorm two
lists with your class: "Fish in the Sea" and "Other Animals
in the Sea." Then divide your class into small groups. After
describing the primary characteristics of fish (animals
with backbones, gills, and scales), have some groups research
the fish list. (If students discover that a listed animal
is not a fish, have them determine what kind of animal it
is.) Ask the remaining groups to research animals from the
other list to discover what kinds of animals they are —
such as mammals, reptiles, mollusks, or echinoderms. Afterwards,
have students create a class mural illustrating each of
the animal groupings.
Mackie Rhodes is the author of two recent
professional development books for teachers, Teaching
With Favorite Kevin Henkes Books (Scholastic, 2002) and
Teaching with Favorite Patricia Polacco Books (Scholastic,
2002). This article was originally published
in the May/June 2002 issue of Instructor.
Download the Conch Shell
Notebook Reproducible.
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