What is Density?
The measure of the denseness in a specific given area of a material is known as its density. It is basically a measure of how tightly matter is packed together. It is a unique property of an object. Archimedes, a Greek scientist, discovered the principle of density. By knowing the formulas and the units, one can easily calculate the density of an object. It is most commonly denoted by or sometimes D.
Density- Examples
Heavy or hard materials are supposed to be dense such as iron, platinum, rocks, minerals, and so on. Materials like glass, bamboo, styrofoam are not dense materials. In matter, liquids are denser than gases and solids are denser than liquids. In the case of gases, particles can move freely all over the place while in the case of solids particles can collide with each other.
Density- Formula
Density is calculated by mass over volume, which can be written as-
\[Density = \frac{Mass}{Volume}\]
\[\rho = \frac{m}{v}\]
where \[\rho\] denotes density
m denotes mass and v volume
Density- SI and Other Units
The density of all different substances is also different which means the density of substances would weigh differently for the same volume of different substances. Therefore, the density of each substance is specific. The standard value for calculating density is taken as 1 g/cm3 which is the approximate density of water. Though, the SI unit of density is taken as kg/m3.
Density can also be expressed in terms of liters, metric tons, as listed below-
t/m3- metric ton per cubic meter
g/mL- gram per milliliter
kg/L- kilogram per liter
g/cm3- gram per cubic centimeter
mg/m3- megagram per cubic meter
kg/dm3- kilogram per cubic decimeter
In the CGS system, the density of objects is measured in g/cm3.
Types of Density
Usually, the density is of two types, one is absolute density, and the other is relative density. Relative density is also known as specific gravity, which is the ratio of the density of a material to the density of reference material. Usually, the reference material is water. Specific gravity is a relative quantity with no units.
Absolute density refers to the mass of any substance per unit volume of a material. It is usually expressed in g/cm3.
To find the density of an object, measure the mass of the material and divide it by the volume it covers, since the density of water is 1 gm/cm3 - the ratio of the density of the material to that of water is 1:£ (Density of water is 1 gm/cm3 at 4°C.)
For example, the density of gold is 19.32 g/cm3, and so the specific gravity is 19.32.
Units of Density
Units of density are g/cm3
The SI units of density are kg/m3.
Other density units - Gram /litre (g/l),
Gram /millilitres
Applications of Density in Real Life
Let's get an idea with an example from real life.
Suppose you have two balloons. One is filled with air, and the other one is filled with coke. Coke is much denser because the atoms take up less space as they move around less. The air balloon contains atoms that are colliding around very quickly, and this makes the atoms take up more space or less density. Thus, the balloon with air is light and the balloon with water is heavy.
Usually, density plays a crucial role in many applications, life tubes we find on beaches or in swimming pools are designed to float on water so that people can swim without sinking, just by holding those air-filled tubes. Life tubes are filled with air which is less dense than water so it always floats. Another application is, ships can float because they have ballast tanks that hold air, and these tanks provide large volumes with little mass, hence decreasing the density of the ship. Combined with the buoyant force, this reduced density helps the ship to float over water. Submarines dive below the surface of the water by emptying their ballast tanks.
Solved Examples
1. Calculate the density of water if it has a volume of 1m3 and mass of 1160 Kg.
Ans: Given-
Mass = m = 1160 Kg
Volume = v = 1m3
Solution:
\[Density = \frac{Mass}{Volume}\]\[\rho = \frac{m}{v}\]
Density = 1160/1
Density = ρ = 1160 kg/m3
2. You have a rock with mass of 60g and density 2 g/cm3. Calculate its volume.
Ans: We know that Density = ρ = Mass/Volume
Volume = v = Mass/Density
Let’s substitute the values given.
Volume = 60/2 = 30cm3
3. If the density of diamond is 3.5 g/cm3, what will be the mass of diamond having a volume of 0.5 cm3?
Ans: Given:
Density = ρ = 3.5 g/cm3
Volume = v = 0.5 cm3
Solution:
We know that Density = mass/ volume
Mass = Density * volume
Let’s substitute the values and find the value of Mass
Mass = 3.5 * 0.5
Mass = 1.8g
FAQs on Unit of Density
1. What are some of the applications of density in real life?
The applications of density in our real lives are vast which includes shipbuilding, pipe design, helium balloons, ice floating on water, and the weight distribution in the airplane. Once you know how to calculate density, you are able to separate various materials such as oil from water. When an oil tank leaks in the ocean, the oil starts to float on the water as it has a lesser density than water.
2. What is meant by immiscible liquids?
The property when two substances are not capable of forming a homogeneous mixture by combining is known as immiscibility and the components are said to be immiscible. Therefore, the liquids that are not able to combine together and form a homogeneous mixture are known as immiscible liquids. In the case of the immiscible liquids, the components of the mixture get separated and the more-dense component will sink and the less-dense component will rise to the top. The most common example of immiscible liquids is oil and water and miscible liquids are alcohol and water.
3. What are the factors affecting density?
The density of a body mainly depends upon the volume and mass of the body. The mass of the body is fixed though the volume of the object can be increased or decreased by increasing or decreasing the temperature and pressure. If the temperature of the body increases, the volume also increases, and as the temperature is decreased, the volume is also decreased. In the case of pressure, as the pressure is increased, the volume of the body decreases while as the pressure is decreased, the volume of the body increases. From this, we can conclude two things which are listed below-
Since the volume and temperature are directly proportional to each other, density is directly proportional to temperature.
Since the volume and pressure are inversely proportional to each other, density is inversely proportional to pressure.
4. What are some of the differences between density and viscosity?
The measurement of the molecular weight of the composition of different components is known as density while the measurement of the forces between the molecules and molecular shapes is known as viscosity. One can determine friction between two layers of a given fluid by calculating the viscosity. There is a slight effect of temperature on density as compared to viscosity though both of them are inversely proportional to temperature. The relationship of viscosity with temperature is mostly exponential while the relationship of density with temperature is usually linear.
To learn more about viscosity, students can visit Vedantu.
5. What is meant by relative density?
At room temperature and pressure, the difference between density and specific gravity is that \[\frac{1g}{1}cm^{3}\]is the density of water, and this density is treated as a standard density and for any other material, the density is calculated relative to this density. Therefore, this density that is calculated is known as relative density, sometimes specific gravity. The relative density of a substance lets us know whether a substance will float or sink. It also gives us an idea about the relative mass.