Water Equivalent
The mass of water that absorbs or releases the exact same amount of heat as a calorimeter body for an identical temperature change.
Governing formula
w = m_cal c_cal / c_water
SI unit
kg (or g)
In depth
Simplifies calorimetry calculations by replacing calorimeter vessel thermal capacity ($m_{cal} c_{cal}$) with an equivalent mass $w$ of water.
Examples in the real world
A copper calorimeter with thermal capacity $42 J/K$ having a water equivalent of $w = 42 / 4184 ≈ 0.010 kg = 10 g$.