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Evaporation of Salt Water

In this activity, you will model the evaporation of salt water. Evaporation of water from the oceans is an important part of Earth’s water cycle.

You will need these materials:

1 sheet of colored construction paper

clear plastic or glass container, just large enough to hold the construction paper

a large drinking glass

3 teaspoons of salt

a teaspoon

one-fourth cup water at room temperature

Hypothesis and Data Collection

Fill the drinking glass with one-fourth cup of water and mix in 3 teaspoons of salt. Mix thoroughly until the salt is dissolved. (You may add a few more teaspoons of water to dissolve it, if needed.) Place the construction paper in the container and gently pour the water on the paper until it is saturated. In part A, predict what will happen in the container overnight.

Part A

What do you think will happen when you leave the paper in the container overnight?

Part B

Now leave the paper in the container overnight. In the morning, look at the paper and write down your observations.

Analyze and Extend

Part A

Were your predictions correct? Explain.

Part B

What process caused the changes that occurred on the paper?

Part C

Evaporation happens in the ocean as part of the water cycle. What fuels evaporation in the ocean?

Part D

Some ocean water evaporates, but certainly not all of it. When evaporation occurs, what happens to the ocean water that doesn’t evaporate? Explain in terms of the salt content and what you saw in the experiment.

Dispose of your waste properly:


Shake the salt off the paper into the trash.

Recycle the paper.

Answer:

Part A:

As salt water evaporates, the water will evaporate leaving behind the salt. Therefore, the paper will become dry and white with salt crystals.

Part B:

The paper will be dry, and white salt crystals will be visible on its surface.

Part A:

Yes, the predictions were correct. As salt water evaporates, the water will evaporate, leaving behind the salt, which will form crystals on the surface of the paper.

Part B:

The process that caused the changes on the paper was evaporation. The salt water evaporated, leaving the salt behind, which crystallized on the surface of the paper.

Part C:

The sun is the primary fuel for evaporation in the ocean. Sunlight provides energy to the water molecules, causing them to move faster and eventually escape into the atmosphere as water vapor.

Part D:

When ocean water evaporates, the water molecules escape into the atmosphere as water vapor, leaving behind the salt. The salt concentration in the remaining water will increase as more water evaporates, eventually reaching a point where the remaining water is too salty for most organisms to survive. This process is known as "salinization" and is a major factor in the formation of salt flats and desert regions. In the experiment, the salt that was left behind on the paper represents the salt that is left behind in the ocean as water evaporates.

Write 3 sentences that you could use to convince a friend or family member to be physically active with you.