a viscometer is used to determine viscosity(density) of a liquid.
This instrument is a balance.
A Balance in Science is an instrument used to measure mass.
This instrument is an adequate type of balance.
mass
Triple Beam Balance.
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balance machine
An aerometer is an instrument used to measure the mass and density of gases.
spectrophotometer
spectrophotometer
This is the analytical balance.
In layman's terms "mass" means weight. The measurement is expressed in grams, and to measure mass, a scale is used.