Editorial board: Martha Merrill

ρ
 20
= ρ
 t
[1-β((20-t)] 
where ρ
 t
is the density of the liquid at the working temperature, kg/m
3
; 
β- average coefficient of volume expansion of liquid 1/⁰C, t- 
temperature of liquid, ⁰C. 
The density of the liquid depends on the temperature. 
The following methods are used to calculate the density: weight, 
hydrostatic, radioisotope and shielding methods are the most widely used 
density measurements in industry. 
The principle of operation of gravity measuring instruments is based on 
the continuous weighing of a certain constant volume of the controlled 
liquid. In addition to measuring the density of pure liquids, weighted density 
meters are also used to measure the density of suspensions and liquids 
containing solids. 
Gas density is defined as 
the mass of the gas occupying a certain 
volume at specified pressure and temperature
. The density is usually 
represented in units of lbm/ft
3
. Another common density representation is 
the ―gas gradient‖ that is expressed in units of psi/ft. 

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INNOVATION IN THE MODERN EDUCATION SYSTEM
126
Fig 1. 
Molar mass and density of common gases.
 
Gas density is a function of the pressure and temperature conditions for 
the gas. Due to its high compressibility, gas can change its volume 
significantly with change in pressure. Therefore, density changes (at low 
pressure) can be significant. At high pressures, the gas molecules are 
packed together and may approach the behavior of liquid (small variation 
of density with pressure). The following two equations are used to calculate 
gas density in the two commonly used units.
The density of a liquid is 
a measure of how heavy it is for the amount 
measured
. If you weigh equal amounts or volumes of two different liquids, 
the liquid that weighs more is more dense. If a liquid that is less dense than 
water is gently added to the surface of the water, it will float on the water. 
Density of liquids is different for different types of liquids, which helps to 
separate them. The density of an item is defined as its mass per unit volume. 
It is denoted by the character D as well as the symbol ρ, ―rho‖. The 
Standard unit of density is kg/m
3
, which stands for kilogram per cubic metre. 
Density may be computed using the equation mass divided by volume. A 
homogeneous substance, such as ice, has identical density throughout 
because its particles are tightly packed collectively. 
SI Unit of Density 

The SI (System International) unit of density is Kg per cubic metre. 

The density of a material is described as the connection between its 
mass as well as the volume it fills. 

It illustrates how heavy an object may be at a fixed volume in 
qualitative parameters. Because the density of various materials varies, 
different materials with identical volumes would weigh differentially.