You can't see the salt in sea water. Explain how you could convince someone that there is salt mixed into the sea water.

1. Collect a Sample: The first step would be to collect a sample of sea water. This can be done by simply filling a clear container with water from the sea.

2. Evaporation: Next, you would need to allow the water to evaporate. This can be done by leaving the container in a sunny spot for a few days. As the water evaporates, the salt that was dissolved in the water will be left behind.

3. Observation: After the water has completely evaporated, you should be able to see a residue at the bottom of the container. This residue is the salt that was mixed into the sea water.

4. Taste Test: If visual evidence is not enough, you could also perform a taste test. By tasting the residue (although not recommended for health reasons), you should be able to identify the salty flavor.

5. Scientific Test: For a more scientific approach, you could use a tool called a refractometer, which measures the amount of light refracted (or bent) when it passes through the sea water. The more salt in the water, the more the light will be refracted.

6. Comparison: Finally, you could compare the sea water to distilled water (which should not contain any salt). By evaporating both and comparing the residue left behind, you should be able to clearly see the difference.

Through these steps, you should be able to convincingly demonstrate that there is indeed salt mixed into sea water.