Density Definition Page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury.
Click on image for full size (23K JPEG)
Image courtesy of Zyra's page

Density is a measure of how much mass is contained in a given unit volume (density = mass/volume). It is usually expressed in kg/m^3, so you would say that a cube 2 meters on each side with a mass of 1600 kg has a density of 1600kg/8m^3 (2000 kg/m^3). Put simply, if mass is a measure of how much ‘stuff’ there is in an object, density is a measure of how tightly that ‘stuff’ is packed together.

One of the ways we can see density illustrated in everyday life is by looking at whether things float or sink in a liquid (water, for example). If an object is less dense than the liquid it is placed in, it will float. If it is more dense, it will sink. This is why an anchor, which is very dense (lots of mass in a relatively small volume) sinks very quickly, while an inner tube (not much mass in a relatively large volume) floats and is very difficult to push underwater.

Some elements are naturally found in very dense forms, and one of the most visually surprising demonstrations of the concept of a less dense object floating on a denser liquid occurs when objects are put in a container of liquid mercury (Hg). This element is a metal that is liquid at room temperature, and it is VERY dense. In fact, it is denser than lead, and metal objects like forks, coins, or even a cannonball will float on top of it!

An activity involving density -- Par 5

Density Definition Page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury.
Click on image for full size (23K JPEG)
Image courtesy of Zyra's page

Density is a measure of how much mass is contained in a given unit volume (density = mass/volume). It is usually expressed in kg/m^3. Put simply, if mass is a measure of how much ‘stuff’ there is in an object, density is a measure of how tightly that ‘stuff’ is packed together.

Some elements are naturally found in very dense forms, and one of the most surprising cases of a less dense object floating on a denser liquid occurs when objects are put in a container of liquid mercury (Hg). This element is a metal that is liquid at room temperature, and it is VERY dense. In fact, it is denser than lead, and metal objects like forks, coins, or even a cannonball will float on top of it!

An activity involving density -- Par 5

Density Definition Page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury.
Click on image for full size (23K JPEG)
Image courtesy of Zyra's page

Density is a measure of how much mass is contained in a given unit volume (density = mass/volume). Put simply, if mass is a measure of how much ‘stuff’ there is in an object, density is a measure of how tightly that ‘stuff’ is packed together.

One way to see how density affects things is to look at how things float or sink in water. If something is more dense than water, it will sink, and if it is less dense it will float. This is why an anchor (very dense) sinks, but an inner tube (not very dense) floats.

An activity involving density -- Par 5

Last modified September 23, 2002 by the Windows Team

The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. Windows to the Universe® is a registered trademark of UCAR. All Rights Reserved. Site policies and disclaimer

Density Definition Page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury. Click on image for full size (23K JPEG) Image courtesy of Zyra's page

Density Definition Page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury. Click on image for full size (23K JPEG) Image courtesy of Zyra's page

Density Definition Page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury. Click on image for full size (23K JPEG) Image courtesy of Zyra's page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury.
Click on image for full size (23K JPEG)
Image courtesy of Zyra's page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury.
Click on image for full size (23K JPEG)
Image courtesy of Zyra's page

This image shows a pool ball floating on liquid mercury. A pool ball is fairly heavy for its size, but you can see it floats on, or is less dense, than liquid mercury.
Click on image for full size (23K JPEG)
Image courtesy of Zyra's page