The **key difference** between Gay-Lussac law and Pascal principle is that **Gay-Lussac law is basically concerned with the properties of gases while Pascal principle is concerned with the properties of fluids.**

Gay-Lussac law and Pascal principal are two important concepts we discuss in physics. Gay-Lussac law is very important to describe the properties of gases. Pascal principle describes some properties of fluids. We can apply Pascal principle in fields such as fluid mechanics, hydraulic engineering, fluid statics, etc. Moreover, we can apply it in many real-world applications such as hydraulic jack, hydraulic press, and force amplifiers in the braking system of most motor vehicles, artesian well, water towers, and dams. It is vital to have a proper understanding of Gay-Lussac law and Pascal principle to excel in such fields.

### CONTENTS

1. Overview and Key Difference

2. What is Gay-Lussac Law

3. What is Pascal Principle

4. Side by Side Comparison – Gay-Lussac Law vs Pascal Principle in Tabular Form

5. Summary

## What is Gay-Lussac Law?

The French chemist Joseph Louis Gay-Lussac first proposed the Gay-Lussac law. There are two relationships in Gay-Lussac law. We call the first one as “law of combining volumes”, and the other one is “pressure-temperature law”.

The law of combining volumes states that when gases react together to form other gases, we can express the ratio between the volumes of the reactant gases and products in simple whole numbers. For this, we need to measure all volumes at the same pressure and temperature. The Gay-Lussac law shows that 1 volume of chlorine and 1 volume of hydrogen would react to form 2 volumes of gaseous hydrochloric acid.

Furthermore, pressure-temperature law states that the pressure of a gas of fixed mass and a fixed volume is directly proportional to the absolute temperature of the gas. We can express it mathematically as P α T, or P/T = k. Here, the pressure of the gas is P, the temperature of the gas is T, and k is a constant. When we consider the same substance under two different sets of conditions, the equation that governs this law is,

P1/T1 = P2/T2

## What is Pascal Principle?

Pascal principle was put forward by the French mathematician Blaise Pascal. Pascal principle states that when pressure increases at any point in a confined incompressible fluid, there is an equal increment of the pressure at every other point in the container. We can express it mathematically as ΔP = ρg(Δh); where hydrostatic pressure (given by pascals) is ΔP, fluid density is ρ, acceleration due to the gravity is g, and height of the fluid above the point of measurement is (Δh).

Moreover, a common application of the Pascal principle is the hydraulic jack, which we use to raise a car off the ground. Here, a small force is applied on a small-area piston. That small force is then transformed into a large force at a large area piston. When the car sits on the top of the large piston, it can be lifted by applying a relatively small force to the smaller piston.

## What is the Difference Between Gay-Lussac Law and Pascal Principle?

Gay-Lussac law was proposed by the French chemist Joseph Louis Gay-Lussac while Pascal principle was put forward by the French mathematician Blaise Pascal. Gay-Lussac law basically describes the properties of gases, but Pascal principle describes the properties of fluids. So, this is the key difference between Gay-Lussac law and Pascal principle. Further, in Gay-Lussac law, there is a direct relationship between pressure and temperature. However, in Pascal law, there is no such direct relationship between pressure and temperature. Therefore, this contributes to another difference between Gay-Lussac law and Pascal principle.

## Summary – Gay-Lussac Law vs Pascal Principle

Gay-Lussac law and Pascal principal are two important concepts in physics. However, Gay-Lussac law is basically about the properties of gases while Pascal principle is about the properties of fluids. Thus, this is the key difference between Gay-Lussac law and Pascal principle

##### Image Courtesy:

1.”Gaylussac” By François Séraphin Delpech – chemistryland.com (Public Domain) via Commons Wikimedia

2. “Pascal law” By DEVENDER KUMAR5908 at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia

## Leave a Reply