home observation science solar system stars our galaxy cosmology astrobiology exoplanets astrophotography
icon Introduction
icon Astronomy Tools
1. Electromagnetic Spectrum
2. Atmosphere Limitations
3. Space Observations
1. Telescopes
2. Radio
3. Space Tools
4. Photography
5. Spectroscopy
6. Computers
7. Advanced Methods
8. Radio Astronomy
icon Basic Mathematics
Scientific Notation
Log Scales
icon Physics
- Basic Units of Measure
- Mass & Density
- Temperature
- Velocity & Acceleration
- Force, Pressure & Energy
- Atoms
- Quantum Physics
- Nature of Light
- Brightness
- Cepheid Rulers
- Distance
- Doppler Shift
- Frequency & Wavelength
- Hubble's Law
- Inverse Square Law
- Kinetic Energy
- Luminosity
- Magnitudes
- Convert Mass to Energy
- Kepler & Newton - Orbits
- Parallax
- Planck's Law
- Relativistic Redshift
- Relativity
- Schwarzschild Radius 
- Synodic & Sidereal Periods
- Sidereal Time
- Small Angle Formula
- Stellar Properties 
- Stephan-Boltzmann Law
- Telescope Related
- Temperature
- Tidal Forces
- Wien's Law
icon Computer Models
icon Additional Resources
1. Advanced Topics
2. Guest Contributions
Physics - Concepts - Mass and Density

In addition to the dimensions of an object - length, width, height, radius and so on - measurements of how much stuff an object is made and how much space the stuff fills are also measured.

Stuff can be anything: hydrogen gas, solid iron, water molecules. An object that contains a certain amount of stuff is said to have mass, and mass is measured by grams, kilograms, and so forth. Do not confuse weight with mass. Generally, weight is measured by pounds, ounces, and so on.

Mass = measure of the amount of matter within an object
Weight = measure of an object along with the effect of gravity.

The chart below demonstrates the difference between mass an weight as compared to location. Let's say I weight 70 kg (I wish):

Earth 70 kg 154 pounds
Moon 70 kg 26 pounds
Jupiter 70 kg 391 pounds
A White Dwarf 70 kg 25,000 pounds

The amount of "stuff" in my body remains the same, thus 70 kg but gravity affects how much I weigh. A White Dwarf  is a very massive stellar remnant, thus my weight will be incredibly high.

On Earth, there is 2.2 pounds per kilograms. For pounds to kilograms, divide by 2.2.

Density and mass provide physical dimensions of a given object, but are completely different in application. While mass measures the total amount of stuff, density is how much individual particles of stuff are within a small space within the object. It is common for density measurement to be based on a centimeter cubed (cm3).

Density represents the mass (or number of particles) per unit volume of a substance, material, or object.

The chart below demonstrates two types of density: mass and particle. Mass density is the mass of an object per cm3 and particle density is how many particles there are in the same space.

Matter Mass Density (g/cm3 ) Particle Density (parts per cm3 )
Water 1 3.7 x 1022
Lead 11.3 3.3x1022
Gold 19.3 5.9x1022
Interstellar Space 2x10-24 1

The three states of matter (solid, liquid and gas) also affect density.

If density and the space filled is known, it is possible to determine mass by the formula:

Back to Top

Search | Site Map | Appendix
©2004 - 2024 Astronomy Online. All rights reserved. Contact Us. Legal. Creative Commons License
The works within is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.