Mass

Mass is a fundamental physical quantity representing the amount of matter in an object. Unlike weight, it does not depend on gravity.

• SI Unit: kilogram (kg)
• Common subunits: gram (g), milligram (mg)
• \( 1\,\text{kg} = 1000\,\text{g} \),   \( 1\,\text{g} = 1000\,\text{mg} \)

Instruments for Measuring Mass

Digital/Electronic Balance

• • Most accurate and commonly used in labs
  • Accuracy: up to 0.01 g or 0.001 g depending on model
  • Displays direct numerical reading

Triple-Beam Balance

• • Uses counterweights on three beams for manual mass measurement
  • Accuracy: around 0.1 g
  • Requires user to balance the pointer at zero

Spring Balance

• • Actually measures weight (force due to gravity), not mass
  • Can be used to estimate mass only under known gravitational field
  • Not suitable for accurate mass measurement

Measuring Mass of Solids and Liquids

Solids:

• • Place the object directly on the balance pan
  • If using a container, measure container mass first and subtract it

Liquids:

• • Use a container (e.g., beaker) and measure its mass \( m_1 \)
  • Pour the liquid and measure new mass \( m_2 \)
  • Mass of liquid: \( m = m_2 – m_1 \)

Precautions and Accuracy Tips

• Ensure balance is placed on a level surface and calibrated properly.
• Use tongs or gloves to avoid adding hand oils/mass to the object.
• For liquids, always use a clean and dry container.
• Zero the balance before placing any object (tare function).