A river does not need to taste like soup to carry dissolved substances. Dissolved means mixed into the water so the separate pieces are no longer visible. Your salt disappeared from sight, but it did not leave the dish.

Rainwater interacts with rocks on land. Weathering, the breakdown and changing of rock, releases dissolved substances. Rivers carry some of them toward the ocean. Processes on the seafloor add substances too.

These sources help explain the ocean’s salt. The story includes movement into and out of ocean water, not just one river filling a giant bowl. Our dish contains table salt that an adult added. It lets you investigate what happens to dissolved salt when water leaves. It does not recreate how all ocean salts formed.

A wet dish can slowly dry without being heated on a stove. Evaporation is the change of liquid water into water vapor, water in its gas form. The water vapor moves into the air.

In your saltwater dish, salt stays behind as the water evaporates. You may see a patch, grains or crystals. The shape and drying time can vary. Waiting is part of the observation.

Ocean water also evaporates while dissolved salts remain. This is one reason water leaving the ocean does not simply take all its salt away. Do not taste the mixture to check it. A drying dish shows separation, but it cannot measure the ocean’s salt balance. When you revisit your first drawing, name what you actually saw and what the reading helped you explain.

together · About 10 minutes plus drying over hours or days; estimate.

You need

• Two shallow dishes
• Water and table salt
• Spoon
• Paper and pencil

Try it

1. Ask an adult to add a small pinch of salt to a little water in one dish.
2. Put the same depth of plain water in the other.
3. Stir and draw what you can see in each.
4. Leave both safely where they will not be spilled.
5. Return as they dry. Draw any residue and compare.