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What you need to know about density determination based on Archimedes' principle.

The video of the buoyancy method test process is as follows:

https://youtu.be/m8P5HJfGI8I

What is the buoyancy method?

The buoyancy method is often used to determine the density of bodies and liquids.

The apparent weight of a body in a liquid, the weight as reduced by the buoyancy force is measured.

This value is used in combination with the weight in air to calculate the density.

Figure 1: Basic procedure for the buoyancy method with below-balance weighing.

Figure 2: Basic procedure for the buoyancy method with a frame for hanging the plummet and a bridge for holding the container for liquid.

In the procedures illustrated in Figure 1 and Figure 2, the values displayed on the weight readout indicate the mass of the immersed body as reduced by buoyancy (see also Figure 3).

Figure 3: The force exerted by a body on a spring scale in air (left) and in water (right)

This means that, in light of the equation

the mass of the body weighed in air is known: m_s = m_(a).

The mass of the liquid m_fl is not directly known, but is yielded by the difference between the weights of the body in air (m_(a)) and in liquid (m_(fl)):

m_fl  = m_(a)- m_(fl)

This changes Equation 1 for determining the density of the body into:

                       Equation 1          

To determine the density of a liquid, mfl is again calculated from the values measured for mass of the body in air and in liquid mfl = m(a) - m(fl) and the result used in Equation3.

The buoyancy method maintains the relationship for determination of the density of the liquid:

              Equation 2

        E quation3.

Vs is the known volume of the plummet used to determine the liquid density.

Thus the density of a substance can be determined in two weighing operations.