3.1.1 Density

• Density

  A measure of how much mass is contained in a given volume of a substance
• ρ (rho)


  Density (measured in kilograms per cubic meter, kg/m³)
• m

  Mass (measured in kilograms, kg)
• V

  Volume (measured in cubic meters, m³)
• Mass


  The amount of matter in an object
• Volume

  The amount of space that an object occupies
• Units of Density

  • kg/m³
  • g/cm³
• 1 g/cm³

  1000 kg/m³
• Calculating Density

  1. Use formula ρ = m/V

  2. Convert units if necessary
• If density needs to be expressed in kg/m³

  5 g/cm³ = 5000 kg/m³
• Floating and Sinking

  An object will float if its density is less than the density of the fluid it is placed in
• Density as a characteristic property

  Density helps identify substances
• Gold has a specific density of about 19.3 g/cm³
• Engineering and Design

  Engineers consider density when designing structures
• Measuring Density in the Laboratory

  1. Measure dimensions for regular shapes

  2. Use water displacement for irregular shapes

  3. Measure mass and volume for liquids
• Water Displacement Method

  1. Fill measuring cylinder with water

  2. Submerge object

  3. Measure new water level

  4. Calculate volume from difference
• To find the density of a liquid, measure its mass and volume directly
• Understanding density helps explain a wide range of physical phenomena and is a fundamental concept in physics
• Density

  A measure of how much mass is contained in a given volume of a substance
• ρ (rho)


  Density (measured in kilograms per cubic meter, kg/m³)
• m

  Mass (measured in kilograms, kg)
• V

  Volume (measured in cubic meters, m³)
• Mass


  The amount of matter in an object
• Volume

  The amount of space that an object occupies
• Units of Density

  • kg/m³
  • g/cm³
• 1 g/cm³

  1000 kg/m³
• 5 g/cm³

  5000 kg/m³
• Floating and Sinking

  An object will float if its density is less than the density of the fluid it is placed in
• Density as a characteristic property

  Density helps identify substances
• Gold has a specific density of about 19.3 g/cm³
• Engineering and Design

  Engineers consider the density of materials when designing structures
• Measuring Density in the Laboratory

  1. Regular shapes: measure dimensions and mass

  2. Irregular shapes: use water displacement method

  3. Liquids: measure mass and volume directly
• Water Displacement Method

  1. Fill cylinder with water

  2. Submerge object

  3. Measure new water level

  4. Calculate volume
• To find the density of a liquid, measure its mass and volume directly
• Understanding density helps explain a wide range of physical phenomena and is a fundamental concept in physics