Density and Specific Gravity Concepts

Density and Specific Gravity Concepts

• Oil floats on water due to its lower density; oil density is 0.92 g/mL compared to water's 1.00 g/mL.
• Heating air in a hot air balloon causes it to expand, resulting in a decreased density, enabling the balloon to rise.

Comparison of Density and Specific Gravity

• Density measures mass per unit volume; specific gravity compares the density of a substance to the density of water (1.00 g/mL).
• Specific gravity has no units because the units of density cancel out in the ratio:
  • Density = mass of substance / volume of substance
  • Specific gravity = density of substance (g/mL) / density of water (1.00 g/mL)

Density Calculation Example

• For an object with a mass of 18.4 g and a volume of 11.2 mL, density is calculated as:
  • Density = mass / volume = 18.4 g / 11.2 mL = 1.64 g/mL

Specific Gravity Calculation Example

• For the same object (mass 18.4 g, volume 11.2 mL), specific gravity is calculated as:
  • Specific gravity = density of the substance (1.64 g/mL) / density of water (1.00 g/mL) = 1.64

Determining Sinking or Floating

• An object with a density greater than that of water (1.64 g/mL) will sink when placed in water.

Volume Calculation from Mass and Density

• For a 15.0 g liquid with a density of 0.875 g/mL:
  • Volume = mass / density = 15.0 g / 0.875 g/mL = 17.1 mL

Mass Calculation from Volume and Density

• For the same liquid with a density of 0.875 g/mL in a volume of 34.6 mL:
  • Mass = density x volume = 0.875 g/mL x 34.6 mL = 30.3 g