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.
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.
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
or,
ρ = m/V
where,
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
Instruments used to measure Density
Hydrometer and Thermometer is used to measure the density of liquids.
| Hydrometer |
| Hydrometer dip in mineral oil and engine oil to measure the Density of these samples |
Density Chart | ||
Material | Density (Kg/m3) | Remark |
Air | 1.2 | At sea level |
Milk | 1027 to 1033 | At 20 oC |
Honey | 1420 | At 20 oC |
Coconut Oil | 925 | At 15 oC |
Cotton Seed Oil | 926 | At 16 oC |
Olive Oil | 918 | At 15 oC |
Sunflower Oil | 919 | At 20 oC |
Rice Bran Oil | 918 | At 20 oC |
Groundnut Oil | 913 | At 20 oC |
Liquid Hydrogen | 70 | At about -255 oC |
Ice | 916.7 | At 0 oC |
Fresh Water | 1000 | At 4 oC |
Plastics | 1175 | Approx for PVC |
Glycerol | 1261 | Also called Glycerine or Glycerin |
Aluminium | 2700 | |
