The key difference between density and weight is that weight is a measure of the amount of matter in an object, whereas density measures the amount of matter in a unit volume.
Density and weight are physical properties of matter. Both properties are related to mass. Moreover, these properties are very useful in physics and engineering when describing objects.
CONTENTS
1. Overview and Key Difference
2. What is Density
3. What is Weight
4. Side by Side Comparison – Density vs Weight in Tabular Form
5. Summary
What is Density?
Density is a physical property of matter, which is a measure of the amount of matter available in a unit volume. It doesn’t change with the size of the sample; hence we call it an intensive property. Density is the ratio between mass to volume and therefore has the physical dimensions of ML-3. Measuring unit for density is often kilograms per cubic meter (kgm-3) or grams per milliliter (g/ml).
When a solid object is put into 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.
Figure 01: Ice Floating on Water
In some specific applications, we can define density as weight/volume. We call it specific weight, and in this case, the unit is Newton per cubic meter.
What is Weight?
Weight is the force applied on an object due to the gravitational field. It is directly related to the mass, and we can give it as the product of mass and gravitational field. Weight has the same dimensions as force (MLT-2), and the units for measurement are Newton or kilogram weight (kgwt).
Since weight is related to the gravitational field, we can measure different weights in different places. For example, the weight of an object at the moon is one-sixth of its weight on earth. Moreover, weight can also differ in different places on earth due to fluctuations in gravity. However, we sometimes consider weight as a constant property.
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.
What is the Difference Between Density and Weight?
Density is a physical property of matter, which is a measure of the amount of matter available in a unit volume while weight is the force applied on an object due to the gravitational field. The key difference between density and weight is that weight is a measure of the amount of matter in an object, whereas density measures the amount of matter in a unit volume. Furthermore, density is an intensive physical property whereas weight is an extensive property.
When considering the units of measurement, weight is measured in Newton, whereas density is measured in kilograms per cubic meter. Apart from that, weight is directly related to gravity while density has no relationship with the gravitational field.
Summary – Density vs Weight
Density is a physical property of matter, which is a measure of the amount of matter available in a unit volume while weight is the force applied on an object due to the gravitational field. The key difference between density and weight is that weight is a measure of the amount of matter in an object, whereas density measures the amount of matter in a unit volume.