A closed surface, such as the space occupied or contained by a substance, can enclose a certain amount of three-dimensional space (solid, liquid, gas, or plasma). The volume of a container is commonly considered to represent its capacity, or the amount of fluid (gas or liquid) that it can hold, rather than the amount of space it occupies.
Fluid displacement may be used to calculate the volume of a solid (whether regular or irregularly shaped). The volume of a gas can also be calculated using liquid displacement.
Its S.I. unit is the cubic meter, and 1m3 = 1000 litres.
The mass per unit volume of a substance is defined as its density. There are so many materials in this world, and each has a different density, or we can say that each has a different mass per unit volume and therefore, properties like purity and buoyancy differ for every known material. Iridium and osmium are the materials that have a higher density than all other materials.
Now talking about the factors which are responsible for the variation in density of a particular material. So, pressure and temperature are the two factors on which it depends.
When we increase the temperature of a material, then the force of attraction between its constituent particles, molecules, or atoms decreases which results in expansion of that particular material, i.e., volume increases, and as the mass remains constant, therefore, the ratio of mass to volume, (mass-volume) decreases and hence, density decreases. So, we end up with the conclusion that density and temperature are inversely proportional to each other.
We notice one thing in our daily life, and that is when we compress any material, its volume decreases. Similarly, when we talk about compression of gas, then obviously its volume decreases with its mass remaining constant, and therefore, density (mass-volume) also decreases, and we find that density and pressure are inversely proportional to each other.
When we say, “density is an intensive property”, then it means that increasing the amount of substance or material does not affect the value of density for that substance.
Example –An iron sphere of 1 kg and an iron cube of 1000 kg both have the same density, i.e., density neither depends on the shape of the substance nor its amount.
ρ=mV where
density of any material
m is mass of material
V is volume covered by the material for the given mass.
When we set a reference to measure the density of a substance, like measuring the density of iron with respect to the density of steel, the general reference to measure the density of liquids is water which achieves its maximum density at 4˚C because at this temperature it has minimum volume and the reference used to calculate the relative density of gases is air (at room temperature).
The other name for relative density is ‘specific gravity.
Some commonly asked questions:
Suppose we have a rod of the length of 10 meters and its mass is 20 kg, then 1 meter of the rod has 2kg mass, and like this, when we define any characteristic value concerning the length, then it is called linear density.
A two-dimensional object is computed by mass per unit area for the density of the surface area (also known as the areal, surface density, or superficial density). Kilogram per square meter (kg. m-2) is the SI-derived unit.
The notion of density is essential because it helps us to determine which compounds will float and which will sink in a liquid. In general, substances float if their density is less than that of the liquid in which they are put.
Normally, when liquids cool, they get denser, but water achieves its maximum density at around 4 ˚C (39.2 Fahrenheit).
It is less dense below this temperature; therefore, when it freezes into ice at 0˚C (32 degrees Fahrenheit), the ice is less dense than the water. This is why ice on water floats and water bodies freeze from the top down.