Difference Between Density and Weight

Density vs Weight

Density and Weight are physical properties of matter. Both properties are related to mass. Both properties are widely used in physics and engineering to describe objects.

Density

Density is a physical property of matter, which is a measure of the amount of matter available in a unit volume. Density of an object doesn’t change with the size of the sample, and hence called an intensive property. Density is the ratio between mass to volume and therefore has the physical dimensions of ML-3. Measuring unit for density may be kilograms per cubic meter (kgm-3) or grams per millilitre (g/ml).

When a solid object is put in to a liquid, it will float if, the solid has a lesser density than liquid. This is the reason for ice floating on water. If two liquids (which do not mix with each other) with different densities are put together, the liquid with a lesser density floats on the liquid with the higher density.

In some specific applications, density is defined as weight/volume. This is known as specific weight, and in this case, unit should be Newtons per cubic meter.

Weight

Weight is the force applied on an object due to the gravitational field. Weight is directly related to the mass, and is given by the product of mass and gravitational field. Weight has the same dimensions as force (MLT-2), and is measured in Newtons or kilogram weight (kgwt).

Since weight is related to gravitational field, different weights are measured in different places. As an example, weight of an object at moon will be one sixth of the weight on earth. Although weight can be slightly different at different countries, sometimes, for the convenience, it is considered as constant.

If the place is the same, the weight is proportional to mass which is a measure of the amount of matter included in the object. Weight is an extensive physical property because it increases when the object size is getting higher.

Difference between Density and Weight

1. Weight is a measure of the amount of matter in an object, whereas density measures the amount of matter in a unit volume.

2. Density is an intensive physical property, whereas weight is an extensive property.

3. Weight is measured in Newtons, whereas density is measured in kilograms per cubic meter.

4. Weight is a force and a vector, whereas density is a scalar

5. Weight is directly related to gravity, and density has no relationship with the gravitational field.