Difference Between Density and Concentration

The key difference between density and concentration is that the density of a substance depends only on the amount of matter within a given volume whereas the concentration depends on the amount of matter and what compound is in there, as well.

Density and concentration are two basic and important topics that we discuss under chemistry and material sciences. Therefore, it is necessary to have a thorough understanding of such concepts before discussing the difference between density and concentration.

CONTENTS

1. Overview and Key Difference
2. What is Density
3. What is Concentration
4. Side by Side Comparison – Density vs Concentration in Tabular Form
5. Summary

What is Density?

Density is an important characteristic of matter. It directly connects with mass. Therefore, getting a clear understanding about it is vital to have a clear understanding of mass. Accordingly, mass is a measurement of inertia of an object. Density, in the most primitive form and it is the mass per unit volume.

For a bulk material with uniform mass distribution, we can easily calculate this parameter by dividing the total mass of the object by the total volume occupied. However, if the mass distribution is not even, we need more complicated methods to measure the density.

Furthermore, we can easily describe the floatation of a substance using its density. Here, the floatation means that a fluid or a uniform solid that is denser than a given fluid will drown in the given fluid. Thus, if the density of the fluid or the uniform solid is lesser than that of the given fluid, it will float on the given fluid. Moreover, we can define the term relative density in order to compare the densities of two fluids. This is the ratio of the two densities and is merely a number.

What is Concentration?

Concentration is another important concept in chemistry. In a qualitative sense, concentration is the amount of a compound in a solution. There are several types of concentrations that we can define. For instance, the mass concentration is the mass of the given compound in a unit volume. Mostly, the units for this parameter is g / dm³, but there are some other units as well.

Moreover, the molar concentration is the number of moles of the given compound in a unit volume. The unit of this definition is mol / dm³. Similarly, the number concentration is the number of molecules of the given compound in a unit volume. The unit of this is dm^-3 (per cubic decimeter). The volume concentration is the volume fraction of the considered compound from the total volume of all compounds before mixing.

All of these concentration terms interconnect with each other. Therefore, we can obtain the molar concentration by dividing the mass concentration by the relative molecular weight of the given compound.

Similarly, we can obtain the number concentration by multiplying the molar concentration by the Avogadro number. And the derivation of the pressure concentration requires the ideal gas equation. On the other hand, we can express the concentration also in ppm, which means parts per million. It is a very useful form when expressing small concentrations. Also, the concentration of a non-dissolvable solid is a constant and does not depend on the volume.

What is the Difference Between Density and Concentration?

Density is the ratio between mass and volume of a substance while concentration is the ratio between the amount and volume of a substance. Therefore, the key difference between density and concentration is that the density of a substance depends only on the amount of matter within a given volume whereas the concentration depends on the amount of matter and what compound is in there, as well.

As another important difference between density and concentration we can say that the density can be given for all three phases of matter while the concentration is given for a solution in liquid phase. A further difference between density and concentration is that the density can be homogeneous or heterogeneous depending on the material. But, concentration is always a homogeneous property.

Summary – Density vs Concentration

Density and concentration are important physical parameters of matter. The key difference between density and concentration is that the density of a substance depends only on the amount of matter within a given volume whereas the concentration depends on the amount of matter and what compound is in there, as well.

Reference:

1. Jones, Andrew Zimmerman. “An Introduction to Density: Definition and Calculation.” ThoughtCo, Oct. 25, 2018. Available here 
2. Helmenstine, Anne Marie, Ph.D. “Concentration Definition (Chemistry).” ThoughtCo, Jun. 22, 2018. Available here  

Image Courtesy:

1.”Density column”By PRHaney – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2.”Dilution-concentration simple example”By FirstPrinciples (Public Domain) via Commons Wikimedia