Today was a practice day for students regarding yesterday’s topic of “density.” Students broke into groups of two and practiced determining the density of eight different objects. This was done by using a scale to measure the object’s mass, using a ruler to help calculate it’s volume, and then dividing. Of course, density = mass ÷ volume.

But some objects were tricky; rocks don’t come in neat cubes or perfect cylinders. So students dropped the rocks into a graduated cylinder full of water and measured how much the water level rose, thus finding the rock’s volume.

When they were done measuring and calculating, the last step was determining flotation. Luckily, there is a convenient trick for determining if an object will float in water. If it’s density is below 1.0 g/ml, the object will float. If it’s above 1.0 g/ml, the object will sink. There were no surprises today. Students discovered that a wooden object will float and a metal object will sink. But they also discovered the science behind why!

September 15 – Density Lab (pg109)