Exploring Density

After spotting the experiment on Nina and the Neurons, Evan said that he would like to explore the liquids that float and sink.  So today was the day.  I started by doing a little research, and found this great video demonstrating density towers.

Good as the video was, I felt that simply replicating it would miss a lot of learning opportunities, so decided to get Evan to create his own density tower by exploring the comparative densities of different liquids he found.

He found:
Water
Milk
Apple Juice
Tomato Ketchup
Sunflower Oil
Vinegar
Washing up liquid
Hair Conditioner
Shower Gel
Aloe Vera Gel

I helped him to explore the comparative densities of the the liquids, all, initially compared to water.  So in glasses we poured out water and each of the liquids.  Before each time, I asked him to make a guess, or hypothesis of what would happen. He varied whether he put the water in first or the other liquid.

As I had watched the video, I had noted that it is important to be careful when pouring on some liquids to prevent inadvert displacement of lower liquids.

We decided to use a blue food colouring in the water to see the distinction between the liquids more clearly after a few liquids got mixed up.

We wrote a chart as we went which placed the different liquids on a scale according to their density compared to each other.  Once we had done this we found a few of the liquids were almost the same density as water and mixed up so that neither colour were distinct any longer.  Namely, vinegar, milk and apple juice.  So we decided to use plain water instead.  Next it was time to differentiate between the liquids which had a greater density than water to see which one we should put on top of each other. Evan guessed that tomato ketchup has the greatest density, so trialled this with putting what he thought was the next, which he thought would be the shower gel.  All his guesses were correct, as it goes, and we simply added them in turn on top of each other, even though we had planned on doing separate little experiments to find out which had the greater density out of two liquids at a time.  Here is the result.

We followed this by exploring the density of solid objects so started by exploring whether objects sunk or floated in water, and then moved on to adding oil on top to see if any of the objects had a smaller density than oil.  This was followed by exploring the greater density objects and liquids together with our findings as shown below.

We both loved looking at the different colours that sat together in this way, and Evan loved it so much he decided he wants a photo of the tower from all angles printed out and stuck onto a tube next for him to have near his bed.  We both noted how amazing the colour of the oil looks, particularly as there appears to be a very strong separation between the oil and water, a kind of film makes the oil base iridescent and very golden.  I think we might go on to have a go at home made lava lamps as an extension of this activity.