Salinity
Salinity is how much salt is mixed into water, like the ocean or a glass of warm water.
Salt dissolves into water the same way sugar dissolves into a glass of juice. A jar of ocean water holds many salt bits spread through every drop. A jar of fresh river water holds almost none. The more salt packed into the jar, the higher the salinity.
Explaining salinity by grade level
When you stir salt into warm water, it seems to vanish. The salt breaks into bits too small to see. The water now tastes salty. More salt means the water has more salinity.
Projects that explore salinity
This project starts with a pail of seawater, which has salt mixed in naturally. You heat the seawater across a range of 20 to 65 degrees Celsius, using ten beakers, and track how warming seawater shifts both its pH and saltiness.
You prepare three jars of salt water and keep each at a different temperature — one at room temperature, one heated with an aquarium heater to 80 degrees Fahrenheit, and one placed in a refrigerator. After five days you use a hydrometer to measure ocean salinity and see how temperature shifts the amount of salt mixed into the water.