Mass density, often just called density, measures how much mass is packed into a given volume. It's calculated by dividing the mass of an object by its volume. To measure it, follow these steps:
Measuring Mass and Volume
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Determine the Mass: Use a scale to measure the object's mass in grams (g) or kilograms (kg). This provides the 'm' in the density equation (ρ = m/v). [Reference: Determining the Density of a Solid and Liquid (video) | JoVE, Measuring Mass and Density - YouTube]
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Determine the Volume:
- Regularly Shaped Objects: Measure the object's dimensions (length, width, height) and calculate the volume using appropriate geometric formulas (e.g., length x width x height for a rectangular prism). Convert units to cubic meters (m³) for consistency. [Reference: Figure out the volume by either measuring the dimensions of the solid or using a measuring jug for a liquid. Convert any units as needed to get a number in meters cubed.]
- Irregularly Shaped Objects: Submerge the object in a known volume of water (e.g., in a graduated cylinder) and measure the increase in water level. This increase represents the object's volume. Again, convert units to cubic meters (m³). [Reference: Figure out the volume by either measuring the dimensions of the solid or using a measuring jug for a liquid. Convert any units as needed to get a number in meters cubed.]
- Liquids: Measure the volume of the liquid directly using a graduated cylinder or other appropriate volumetric glassware. Convert units to cubic meters (m³). [Reference: Figure out the volume by either measuring the dimensions of the solid or using a measuring jug for a liquid. Convert any units as needed to get a number in meters cubed.]
Calculating Density
- Calculate Density: Divide the mass (m) by the volume (v) to obtain the density (ρ). The formula is: ρ = m / v. The resulting units will be kg/m³ or g/cm³. [Reference: Divide the mass by the volume to figure out the density (p = m / v).]
Examples
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Example 1 (Solid): A rectangular block of wood with dimensions 10cm x 5cm x 2cm has a mass of 100g. Its volume is 100 cm³ (10 x 5 x 2). Therefore, its density is 1 g/cm³ (100g / 100cm³).
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Example 2 (Liquid): 50 ml of a liquid has a mass of 60g. Since 1 ml = 1 cm³, the volume is 50 cm³. The density is 1.2 g/cm³ (60g / 50cm³).
Advanced Techniques
More sophisticated methods exist for measuring density, particularly for specialized applications. These include techniques like using a suspended microchannel resonator [Reference: Measurement of mass, density, and volume during the cell cycle of ...], or resonator oscillation frequency variations [Reference: A Reliable Flow-Based Method for the Accurate Measure of Mass ...]. These methods are often used for microscopic samples or materials with unique properties.
