A year ago, I taught a grade 9 applied Math class. It consisted of 11 boys and 3 girls. These were students who did not enjoy math, let alone understand it. Many of them had IEP’s, and a few were performing at below grade level.

One day, in the middle of a lesson, a student proclaimed, “Science is more important than Math!”. I was taken aback since I think there is a lot of Math in Science. Clearly, some of these students understood more in Science class than they did in Math class.

So, I made an attempt to explain to them how there is Math in Science – through the concept of density. In plain language, why ice floats on water.

Water has a density of 1 g/mL – in other words, the volume in mL also equates to the mass in g. Density is the rate of mass per volume, in this case, g/mL. So let’s say we have 10g of water. It’s volume would be 10mL.

If we freeze one of the containers of water, it’s volume increases. This is because water expands when frozen. Take a look at this video to see what happens to water at the molecular level during the phase change.

So, if the mass remains the same but the volume increases, this makes the density decrease. Comparing the density of ice to water, ice is less dense, which makes it float on water.