VOLUME – EXPLAINED!
Remember – volume is the amount of space that something takes up! That something can be a
solid or a liquid. It gets really confusing, because many people think that volume is the same as
mass, or weight. Mass or weight is the amount of an object there is, where volume is the amount of
space it takes up. There is a difference!
How do we take the volume of a solid? If it is a perfect cube or square object, we simply multiply:
Volume = Length x width x height
If we are looking at something that is not a perfect cube, we have a different way to figure out the
volume. A cylinder has a volume of:
Volume = π r2 h
radius
height
And a sphere has a volume of
Volume = 4 π r3
radius
3
What if we are dealing with a liquid? We just use a graduated cylinder! Not a beaker, remember,
because the lines aren’t very accurate, but a graduated cylinder!
What if we are dealing with something, though, that is a solid, but not a regular solid? Remember
the bubble gum lab? How did we figure out the volume of the bubble gum after it was chewed? Or
when we did the Measurement Olympics Lab? How did we figure out the volume of the penny?
We used something called water displacement! An object that is placed in water will push aside as
much water as its own volume! So, if an object has a volume of 2 liters, if you stick it in some
water, it should push aside 2 liters of water!
To get a REAL accurate volume, though, you need to
carefully place the object in the water, and hold it there
with a piece of string, so it is totally covered with water,
and doesn’t touch the sides or bottom. Why do you think
this is?
One more thing – and it is important! Sometimes scientists
like to go between solid and liquid volumes. For example, what
if I had a cube that was 1cm by 1cm by 1cm, as in the picture:
1cm
= 1 mL of water
1cm
1cm
The volume of this cube would be 1cm x 1cm x 1cm = 1cm3.
If you could hollow out this cube, and fill it with water,
it could hold 1 ml of water. So, scientists and doctors say that
1cm3 = 1 mL or 1cc