Wherever you live, your class can explore the sand and the sea with our “sun-sational” theme unit
- Grades: PreK–K, 1–2, 3–5, 6–8
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.
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.
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.
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.
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.
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 (PDF) 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.