We must have all noticed that the weight of objects can vary greatly. A plastic teaspoon weighs less than a metal one, and a gold ring weighs twice as much as a silver one, even if the objects are exactly the same size.
The density of a material is a measure of how ‘squashed up’ it is, and a dense object contains more mass than a light object of the same size.
Density of a substance is defined as its mass per unit volume.
where d– Density, M-mass, and V-volume of the substance.
It is a scalar quantity.
Note that the density of water is , and the rule is that an object of greater density will sink in a liquid of lower density. So, perhaps not surprisingly, the brick will sink in water. But will it sink in mercury? See the table right.
Density of some substances
|Metal or alloy||kg/cu.m|
|aluminium – melted||2560 – 2640|
|aluminium bronze (3-10% Al)||7700 – 8700|
|aluminium foil||2700 -2750|
|antifriction metal||9130 -10600|
|beryllium copper||8100 – 8250|
|brass – casting||8400 – 8700|
|brass – rolled and drawn||8430 – 8730|
|bronze – lead||7700 – 8700|
|bronze – phosphorous||8780 – 8920|
|bronze (8-14% Sn)||7400 – 8900|
|cast iron||6800 – 7800|
|electrum||8400 – 8900|
|light alloy based on Al||2560 – 2800|
|light alloy based on Mg||1760 – 1870|
|monel||8360 – 8840|
|nickel silver||8400 – 8900|
|steel – rolled||7850|
|steel – stainless||7480 – 8000|
Determination of Density of a regular shaped object
1. First weigh the given solid in a physical balance and find its mass m.
2. Then measure the dimensions of the solid with the help of a meter rule (or vernier or micrometer) and calculate its volume V and use the formula
Determination of Density of a irregular shaped solid
1. First weigh the given solid in a physical balance and find its mass
2. Now take a suitable liquid (which does not react with the solid and in which the solid sinks) in a clean measuring cylinder. Note the level of the liquid in the cylinder. Then immerse the given solid completely into the liquid and note the reading again. The difference in the readings give the volume of the solid. Now use the above formula to find its density.
Determination of Density of an irregular shaped solid(Try it now)