The main difference between viscosity and density is that Viscosity is the measure of fluid resistance to the flow. Density, on the other hand, is the measure of mass per unit volume of a given substance.

Even though there is no direct relation between the two, they are very useful quantities when describing the dynamics of the given fluids (liquid or gases).

In this exclusive article, I am gonna walk you through some of the most significant differences between these two. So, without wasting any time, let’s dive right in…!!!

## 10 Differences Between Viscosity and Density

Viscosity | Density | |

1. | Viscosity is the measure of fluid resistance to the flow. | Density is the measure of mass per unit volume of a given substance. |

2. | Viscosity decreases with an increase in temperature. | Density also decreases with an increase in temperature. |

3. | The symbol for viscosity is (η) eta. | The symbol for density is (ρ) rho. |

4. | Viscosity increases with an increase in pressure. | Density also increases with an increase in pressure. |

5. | Temperature, pressure, and shear rate are determining factors in terms of viscosity. | Temperature and pressure are determining factors in terms of density. |

6. | Viscosity is measured using Viscometer. | Density is measured using Hydrometer. |

7. | The SI unit of viscosity is Pa·s (Pascal second) or cP (centipoise). | The SI unit of density is kg/m³ (kilogram per cubic meter) or g/cm³ (gram per cubic centimeter). |

8. | The formula for Viscosity is F/A = η(dv/dx). | The formula for density is ρ = m/V. |

9. |
Viscosity is used to design equipment such as pumps, pipes, and turbines, etc. | Density is used to study fluid mechanics and in the design of tanks, ships, submarines, etc. |

10. | Water has a lower viscosity, while honey has a high viscosity. | Aluminium has a lower density, while steel has a high density. |

## What is Viscosity?

By definition, viscosity is the measure of fluid resistance to the flow. One can also say that it is a measure of a fluid’s resistance to flow. By knowing viscosity, we can easily determine the thickness and thinness of any given fluid.

It is basically used to understand the effects on flow behavior such as whether the flow of the fluid is laminar or turbulent. Temperature, pressure, and shear rate are determining factors in terms of viscosity.

Viscosity can be variable for different types of fluids. For example, Newtonian fluids have a constant viscosity regardless of the shear rate. Non-Newtonian fluids, on the other hand, have a variable viscosity depending on the shear rate.

**Types of Viscosity**

In general, there are two types of viscosity. These are Dynamic Viscosity and Kinematic Viscosity. By definition, **Dynamic Viscosity** is the measure of internal resistance of the fluid against the flow.

Whereas, **kinematic viscosity** is the ratio of dynamic viscosity to density. It is also known as Momentum Diffusivity. Mathematically, it is given by:

where,

ν = Kinematic Viscosity

ρ = density of a fluid

μ = Dynamic Viscosity

**Properties of Viscosity**

Some of the properties of viscosity are:

- Viscosity decreases with an increase in temperature.
- Viscosity increases with an increase in pressure.
- Viscosity affects flow behavior
- Viscosity is a scalar quantity, etc.

## What is Density?

By definition, Density is the measure of mass per unit volume of a given substance. One can also say that density is a measure of how much mass is contained within a given volume of a substance. It is an important physical property in science and engineering applications.

Because it can be used to identify and characterize different materials, to calculate the amount of material needed for a given application, and to predict how substances will behave in different environments.

**Types of Density**

In general, there are two types of density. These are absolute density and relative density. **Absolute density** is the ratio of the mass of material to the volume of the material.

Whereas, **Relative Density** also known as “Specific Gravity” is the ratio of the density of the material to that of a standard material, usually water.

**Properties of Density**

Some of the properties of density are:

- Density is directly proportional to the mass.
- Density is inversely proportional to the volume.
- Density decreases with an increase in temperature.
- Density increases with an increase in pressure.
- Density is a scalar quantity, etc.

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