Density

• Density helps us understand how tightly packed together particles of matter are within a substance.
• The densities of pure substances do not change from one sample of this substance to another. Therefore, density can be used to help identify one pure substance from another.
• Density is defined as the mass of a substance divided by the amount of space that it takes up (volume).
• To determine density two things must be known: 1.) the mass of the substance (in grams or kilograms); 2.) the volume of the substance (in milliliters or liters).
• Mass is usually determined by using a scale (similar to a bathroom scale).
• Volume can be determined in three ways:

1. Fluids - use a graduated cylinder to measure the volume.
2. Regular Shaped Solids (cubes, etc) - use the formula, length x width x height, to find the volume in cm3 or m3 .
3. All solids - displacement, begin with a known volume of water (initial volume), place the object in water, the volume of water will increase, find this new volume level (final volume), subtract the final volume and initial volume.

Necessary Formulae

• Final Volume - Initial Volume = Volume

Volume by Displacement:

• Initial Volume - volume of the water prior to placing the object within it.
• Finial Volume - volume of the water after placing the object within it.