Lots of Colored Water

We filled a basin with water at 22ºC before inserting two bottles full of colored water into it. The colored water had two different characteristics, and here were our findings.

TEST 1

Green:

cold water @ 5.8ºC

the water sank to the bottom of the basin

this was expected, because cold sinks

Red:

warm water @ 34.2ºC

the water rose to the top of the basin

this was expected, because heat rises

Conclusion:

Heat rises, so this was expected. In cold water, the atoms are moving slower, so it sinks, and since in hot water the atoms are moving really quickly, and it rises.

TEST 2

Green:

high salinity water @ room temperature

14g of salt

the water dispersed faster and sunk to the bottom of the basin

Red:

normal salinity water @ room temperature

3.5g of salt

dispersed quickly, but slower than the green

the water rose slightly higher than the green

Conclusion:

The salinity weighs down the water, so the water with more salt is heavier, and really sticks to the bottom.

TEST 3

Green:

normal salinity water @ 37ºC (warm water)

3.5g of salt

water dispersed somewhat slowly, and sunk directly to the bottom

Red:

high salinity water @ 37ºC (warm water)

14g of salt

dispersed quickly and sunk directly to the bottom

Conclusion:

The amount of salt weighed down the water, as evidenced by how the red water, which had higher salinity, escaped from the bottle more quickly than the low salinity water. The salt also weighs the water down so much that the salinity overpowers the temperature. Heat normally rises, but the weight of the salt made the warm water sink to the bottom as if it were cold.

According to the NOAA, this affects the real world in the same way. "Winds drive ocean currents in the upper 100 meters of the ocean’s surface. However, ocean currents also flow thousands of meters below the surface. These deep-ocean currents are driven by differences in the water’s density, which is controlled by temperature (thermo) and salinity (haline). This process is known as thermohaline circulation.

In the Earth's polar regions ocean water gets very cold, forming sea ice. As a consequence the surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. As the seawater gets saltier, its density increases, and it starts to sink. Surface water is pulled in to replace the sinking water, which in turn eventually becomes cold and salty enough to sink. This initiates the deep-ocean currents driving the global conveyer belt." (NOAA)