Chemistry Podcast

Friday, 4 February 2022

What is Density in Chemistry - Definition, Symbol, SI Units, Formula & Measurement of Density

Definition, Symbol, SI Units, Formula & Measurement of Density

Density is simply mass per unit volume. Density of many samples is measured in labs for example in oil and gas industry. They define density in general way as 'weight per unit volume' although 'weight per unit volume' is not density it is 'Specific Weight' so density is 'mass per unit volume'

Example of Density

Don't worry! we will going to learning density in very simple way, with examples.
Do you ever see a dry WOOD piece floating over water in river or pool? 
Yes, We all see that, Do you think why it floats. Because density of wood 🪵 is lesser than density of water 💧 so piece of 🪵 wood experience upthrust force and float on water 💧. 

Take another example of Iron Metal piece and water. IRON METAL piece has higher density than WATER, so piece of iron metal sink in water.

To understand clearly, we will take another example of 'Sunflower Cooking oil' & 'Water'. When we mix 'Sunflower Cooking oil' & 'Water', after some time oil comes at top and water set below (means separate out). So now question is why this happens? Answer is due to difference in density & nature of water and oil. Oil is nonpolar while water is polar molecule so they don’t interact with each other. 
Density of Sunflower Cooking oil is 919 Kg/m3
Density of Water is 1000 kg/m3

What is Density in Chemistry

In science/chemistry, density of a substance is its mass per unit volume.  Density is also known as "Volumetric Mass Density". 

Generally different materials have different density. Chemical element Osmium (Os having atomic number 76) is naturally occurring densest element. To simplify the comparison of densities of different materials or liquids it is needed to replace density with "relative density" as relative density is dimensionless quantity. Relative Density is also called "Specific Gravity". 

Specific gravity or relative density is the ratio of density of sample material to the density of standard material. Generally water is taken as standard material. If we take water as standard material than if we get relative density of a material is less than '1' means that material floats in water. Water has highest density at 4 °C i.e. 1000Kg/m3.

Density of material depends on the temperature and pressure. Effect of temperature and pressure is very less on solid and liquid but effect of temperature and pressure is very high on gases. If we increase pressure on given material than its volume get decrease that result in increase in density, similarly If we decrease pressure on given material than its volume get increase that result in decrease in density. 

And in case of temperature, if we increase temperature on given material than its volume get increase that result in decrease in density, similarly if we decrease temperature on given material than its volume get decrease that result in increase in density. 

But their are some exceptions which do not follow these rules, one of them is water means when temperature of water decreases than it makes solid ice which float on liquid water as ice have less density than liquid water i.e. Density of ice is 916.7 Kg/m3 at 0 °C, and water has a density of 999.8 Kg/m³ at 0 °C.

Definition of Density

                           Density of a material is defined as its mass per unit volume.

Symbol of Density

                             Symbol of density is 'ρ' or 'D' and pronounces as 'rho'.

Formula of Density

                             Density = Mass/Volume
           ρ = m/V
           ρ is density, m is mass and V is volume.
  • When numerator (mass) is much larger than denominator (volume) in density formula, that shows the given substance has higher density, but when denominator (volume) is much larger than the numerator (mass), that shows the given substance has lower density.

SI Unit of Density

                             SI Unit of Density is Kg/m3 or g/cm3

Density Calculator

    Density is calculated by dividing mass by volume. Density is measured as units of mass/volume, often g/cm3, g/Kg3 or g/mL. Just enter value of mass and volume to get density.

Instruments used to measure Density

Weighing balance, Scale, Hydrometer and Thermometer are some instruments used to measure the density of solids & liquids.

How to Measure Density of a Solid

Just watch below video to learn how to measure density of a solid.

Hydrometer to measure Density

Hydrometer dip in mineral oil and engine oil to measure the Density of these samples
Hydrometer dip in mineral oil and engine oil to measure the Density of these samples

Density Chart

Density (Kg/m3)
At sea level
1027 to 1033
At 20 oC
At 20 oC
Coconut Oil
At 15 oC
Cotton Seed Oil
At 16 oC
Olive Oil
At 15 oC
Sunflower Oil
At 20 oC
Rice Bran Oil
At 20 oC
Groundnut Oil
At 20 oC
Liquid Hydrogen
At about -255 oC
At 0 oC
Fresh Water
At 4 oC
Approx for PVC
Also called Glycerine or Glycerin
Chief ore of Aluminium is Bauxite
Precious stone
Zinc is found in cells throughout the body.
Used since ancient times
Found in the Earth's crust only in chemically combined form
Silvery-white lustrous metal
Very high thermal and electrical conductivity
Highest electrical conductivity, thermal conductivity
Soft, malleable, and heavy metal
Only metallic element that is liquid at room temperature
weakly radioactive because all its isotopes are unstable
Densest naturally occurring element
Densest naturally occurring element

Thank for reading! 
You can also learn some interesting topics given below or search in search button above for interesting chemistry terminology &  facts.

1 comment:

Anonymous said...

1. Surface Tension (Capillary action - Capillary tube)

2. Consistency

3. Viscosity

4. Contact Angle

5. Density

6. Fash point

Surface Tension - Tensiometers are used, which calculate the force needed to break through the liquid surface.
Consistency - A pile of the sample is enclosed in a container of fixed volume. The container is opened and the time measured for gravity to pull the sample a fixed distance. This instrument is called a Consistometer.
Viscosity - The measurement of the friction between the molecules in a flowing liquid is measured by an instrument class known as Viscometers.
Contact Angle - Contact Angle Instruments measure the angle between a drop and the surface of the substrate. They are sometimes known as goniometers.
Density - Density is measured by comparing the weight of a volume of the test sample with the weight of the same volume of a standard liquid.
Color, Odour, taste, Solubility, Melting point & Boiling point, specific heat, thermal conductivity, surface tension, dipole moment, Vapour presure, Refractive index, density, temperature, humidity, viscosity, dynamic viscosity, kinematic viscosity, acidity pKa & Basicity pKb, Thermal conductivity, Crystal structure, Molecular shape, Point group, dipole moment, specific heat capacity, std enthalpy of formation, std molar entropy, gibbs free energy.


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