### Video Transcript

A substance has a mass of 13.5
grams and occupies a volume of five centimeters cubed. What is its density?

Density is a value or number we
give to a substance or object when we take its mass and divide this value by its
volume. Mass is usually measured in grams,
symbol lowercase g. And volume is usually measured in
cubic centimeters, symbol cm to the power of three. Density has the unit grams per
centimeter cubed, symbol g forward slash cm to the power of three.

We can define density as the amount
of mass per unit volume in a substance. The density value of a substance
tells us how compact the substance is. In other words, it tells us how
closely the particles are packed. In a balloon, the air particles are
not packed closely together. The particles are rather far
apart. Air in balloons has a low
density. The particles in a stone or an iron
nail are closely packed. These objects have a high
density.

The question asks us to determine
the density of a substance. We are given its mass of 13.5
grams. And we are given its volume of five
centimeters cubed. We can put these two values into
the equation. We put 13.5 grams at the top for
the mass and five centimeters cubed at the bottom for the volume. Then, we can divide the two
numbers. This gives us an answer of 2.7.

Next, we can figure out what the
units will be. We have grams at the top and
centimeters cubed at the bottom. This gives us the unit grams per
centimeter cubed in the answer. We have already seen that this is
the unit for density. This unit is what we expected. So, the density of the substance is
2.7 grams per centimeter cubed.

Is this density value high or
low? We cannot say by just looking at
the answer. But we can compare it with the
density of a substance we know. Water has an easy density value to
remember. Water’s density is one gram per
centimeter cubed. So the substance in the question
has a density value bigger than the density of water. This means that if this substance
was placed into water, and if it didn’t dissolve, it would sink.

Finally, what is the density of a
substance with a mass of 13.5 grams and a volume of five centimeters cubed? The answer is 2.7 grams per
centimeter cubed.