Mass and Weight Facts

Mass and weight are two totally different things. Mass is the actual amount of matter that is contained in an object. Weight is the gravitational force that is pulling on an object.

An example would be two cups of popcorn compared to two cups of dirt. The dirt has more mass because it has more matter.

The popcorn may look like it has a lot of mass, but it is filled with air. The dirt will also weigh more than the popcorn.

Mass is the number of atoms that are packed into an object as well as the type and density of the atoms.

The amount of weight that an object has will vary, depending upon the mass and the gravity strength.

  • When scientists want to convey an object’s mass in relation to atoms and molecules they use the term ‘atomic mass unit’ (u). This means one atomic mass unit is equal to 1/12 of the mass of carbon-12.
  • In the science of physics, there are two ways to configure mass: inertial mass and gravitational mass.

Inertial mass is configured by how much an object resists acceleration. An example of this might be to put a bowling ball next to a baseball on the floor. Push both with the same amount of strength. The bowling ball will not go as far because it’s mass resists.


  • Gravitational mass is configured by how much gravity an object exerts on other objects –or- how much gravity the object experiences from another object.
  • The closer you are to the center of the Earth, the more an object will weigh. If you took that same two cups of dirt to a high mountain, it would weigh less than at sea level.

The moon’s gravity is one-sixth the gravity of earth. If you stood on the moon, you would therefore weigh one-sixth less than on earth.

  • While the weight may vary depending upon the location and gravitational pull, the mass of an object always stays the same.
  • When talking about how heavy something is, scientists also use the term of ‘mass’.
  • The smallest mass that is known is the ‘photon’. It has a mass that is 5.3 times 10- 63 (that is 62 zeros and a 1 after the decimal point).
  • The earth’s mass is 6 x 1024 (six trillion) kg.
  • They believe the mass of the Universe might be 10 51 (that is the number ten, followed by 50 zeros) kg.

The amount of mass that is within a certain space is called ‘density’ and is measured in grams per cubic centimeter or g/cm3. Using the example of the popcorn and the dirt, you could see how the ‘density’ of the popcorn would be less than that of the dirt as the dirt has more mass compacted in a specific space.

The lightest solids that are known are called ‘silica aerogels’. They have a density of .005 g/cm3. They are used in space science and more recently in an experiment to capture small space particles.

  • The lightest gas that is known is hydrogen. It has a density of 0.00008989 g/cm 3. Whereas, the density of air is 0.00128 g/cm3.
  • The highest density of a solid is osmium which is 22.59 g/cm 3, compared to lead which is 11.37 g/cm3.
  • The density of a neutron star is incredible. It is around one billion trillion g/cm3.

Weight in measured in the United States in pounds and in other parts of the world in kilograms.

In physics, we often describe weight as a force and that is measured in Newtons (n).

It is named after the famous scientist, Isaac Newton.