about density

We started this experiment very simply, by putting one drop of food coloring in cold water and one in hot. Simply put, the cold water is more dense than the hot water, as are other fluids such as air. When air warms it rises. This concept is responsible for what we know as convection currents found in weather and plate tectonics. The hot fluid moves up while the colder fluid sinks back down to get heated back up. This process keeps going and going and going.

When we saturated the water with salt, we made the water much more dense. It was almost so dense the solution could not hold anything else, not even one drop of food coloring, which is why it did not dissipate the way it did in the "pure" water solutions.

Next we then learned water and oil don't mix! Because they do not mix, scientists call them immiscible liquids. When we look at the glass with the water and the oil, the oil is on top of the water. This is because the one drop of oil weighs less than one drop of water. Scientists call this density and items that are less dense than water will float, those that are more dense, like salt, will sink.

To continue on with our experiment we poured salt in. It sank to the bottom taking some olive oil along with it. Remember, oil and water are immiscible so the oil returns to the top, which causes the movement within the solution.

All in all it is a great experiment and if you have not tried it, you should!