The question, “What are the 5 gas laws in physics?” may have been posed to you if you are here, or something akin to Ideal Gas Law, Boyle’s Law, Charles’s Law, Gay-Lussac’s Law, or Avogadro’s Law.

Introduction

Gas laws form the basis of thermodynamics. They are taught to high school students as a part of physics and/or chemistry. The behaviour of gases is governed by these rules in various situations. They help to understand the relationship between the properties of gases, namely:

• Pressure
• Volume
• Temperature
• Quantity

Understanding these relationships enables scientists and engineers to predict how gases will behave in different situations. It also enables them to design efficient systems and processes that assist us in our daily lives.

Overview of Fundamental Concepts

To comprehend the core of gas laws, we must get familiar with the basic ideas.

Pressure

Pressure is the measure of the intensity of collisions between gas molecules and the walls of the container. These collisions (force) per unit area are defined as pressure.

The air in our surroundings continuously exerts pressure on us, which is called the atmospheric pressure. At sea level, the value of atmospheric pressure is 101325 Pa, or 1 bar or 1 atm. As we climb, this atmospheric pressure starts to drop due to a decrease in air density.

Volume

Volume is the measure of space and can be defined as the total amount of space that gas molecules occupy in three dimensions. It is typically measured in litters (L) or cubic meters (m³).

Temperature

Temperature, which is a measure of the average kinetic energy of molecules, influences the volume and pressure of a gas. It also affects the frequency and speed of collisions between gas molecules.

Quantity

Quantity is a measure of the number of particles in a gas sample; it is often referred to as the amount of substance. The unit of measurement of the amount of substance is moles, and Avogadro’s number is the approximate number of molecules or atoms in 1 mole of a substance, which is 6.022 x 10²³.

Definition of Gas Laws

A set of fundamental principles to explain the behaviour of gases under different physical conditions is known as gas laws. These laws are important for a wide range of disciplines, e.g.,

• In physics, they help in describing the movement of gas molecules in different states of matter.
• In chemistry, they are used to evaluate chemical reactions involving gases.
• In environmental science, they aid in understanding weather conditions, atmospheric phenomena, and air quality.
• In engineering, they are applied in the design of systems involving gases, such as engines and refrigeration units.

Historical Overview of the Development of Gas Laws

The study of gas behaviour has a rich history that dates back to ancient times. However, the most earnest work on the gas laws began in the 17th century, when scientists started to explore the properties of gases. Some notable scientists include Robert Boyle, Jacques Charles, and Joseph Louis Gay-Lussac.

The development of the fundamental gas laws was due to the early experiments of these scientists. It laid the foundation for further discoveries and paved the path for the development of the ideal gas law.

Subsequent research and experimentation have enhanced and refined our understanding of gas behaviour, and, hence, led to the establishment of additional gas laws.

Significance of Gas Laws in Thermodynamics

To understand how properties like pressure, temperature, volume, etc. of a gas change, gas laws play a fundamental role. They serve as a framework for analysing and predicting phenomena like:

• expansion of a balloon with air
• combustion of air-fuel mixture in an engine
• behaviour of gases in Earth’s atmosphere, etc.

What Are the 5 Gas Laws in Physics?

The 5 gas laws serve as a guiding path in scientific and industrial applications. They not only enhance our understanding of how gases behave under different conditions but also provide valuable insights into the relationship between different properties of gases. These laws comprise:

• Boyle’s Law
• Charles’s Law
• Avogadro Law
• Gay–Lussac’s Law
• Ideal Gas Law

Boyle’s Law

Boyle’s law, Boyle–Mariotte law, or simply Mariotte’s law are the same names in thermodynamics. It is one of the fundamental gas laws, most commonly known as Boyle’s Law, and named after Robert Boyle, who was an Irish scientist. This law states that:

For a certain amount of an ideal gas present in a cylinder, the pressure is inversely proportional to the volume, given that the temperature remains constant.

Boyle’s Law is also known as the constant temperature law (an isothermal process).

Mathematical Formulation and Its Interpretation

For a gas that is enclosed in a cylinder and has pressure P and volume V at a constant temperature T, Boyle’s Law can be written as:

P ∝ 1/V

P = (constant) × (1/V)

P = (k) × (1/V)

PV = k

Let us assume that before expansion, the initial pressure and volume of the gas were P₁ and V_1, and after expansion, the final pressure and volume were P₂ and V₂. In that case, the last equation can be written as:

P₁ V₁ = k

P₂ V₂ = k

Equating the two equations gives:

P₁ V₁ = P₂ V₂

It is evident from the above equation that for an ideal gas, the product of the initial pressure and volume of the gas and the product of its final pressure and volume are the same, given that its temperature remains constant.

In other words, the equation shows that pressure and volume are inversely interconnected. It means that when there is an increase in pressure, it will result in a decrease in volume, and vice versa.

Significance of Boyle’s Law

In many real-world applications, Boyle’s Law is the best tool to understand and predict the behaviour of gases. It helps us with everything, from everyday tasks to complex scientific and technological activities.

Real-World Applications and Examples

Scuba Diving

Boyle’s Law is pivotal in scuba diving, governing how air behaves in tanks as divers descend and ascend underwater. With increasing pressure at depth, the volume of air in tanks decreases, leading to denser air consumption.

This affects buoyancy, heightening the risk of sinking, and introduces dangers related to nitrogen content absorption, such as nitrogen narcosis and decompression sickness.

Understanding Boyle’s Law helps divers effectively plan, monitor, and follow safety protocols for a secure and enjoyable underwater experience. During a dive, divers primarily focus on monitoring the pressure gauge to track changes and ensure their safety.

Soda Cans and Bottles

In a soda can or bottle, carbon dioxide is filled under pressure as it imparts sparkle and a tangy taste and prevents spoilage. When the can or bottle is opened, the gas pressure drops, allowing the dissolved gas to rapidly escape, forming bubbles and resulting in the characteristic fizziness of the drink.

Pneumatic Systems

• Pneumatic impact wrenches are commonly used for tightening and loosening nuts and bolts in the automotive and manufacturing industries.
• Pneumatic nail guns are employed in construction and carpentry for rapid and efficient nailing of materials.
• Pneumatic riveters are used for joining metal pieces together in DIY metalworking projects and repairs.
• Pneumatic tire inflators come in handy for inflating the tires of bicycles, cars, and other vehicles at home.

These are just a few examples of industrially and domestically used pneumatic tools. All of the tools, mentioned above, work based on Boyle’s Law, as changes in pressure and volume of the compressed air are essential for their functionality.

In these pneumatic tools, compressed air is used as the source of power. The air in these tools is compressed in a closed chamber, which reduces its volume. As a result, there is an increase in the pressure of the enclosed air in the chamber. The pressurised air then performs various tasks, such as driving nails, powering drills, or operating impact wrenches.

Charles’s Law

Charles’s Law, or Gay-Lussac’s Second Law, is the same name in thermodynamics. It is one of the fundamental gas laws, most commonly known as Charles’s Law, and named after Jacques Charles, who was a French scientist. This law states that:

For a certain amount of an ideal gas present in a cylinder, the volume is directly proportional to the absolute temperature, given that pressure remains constant.

Charles’s Law is also known as the constant pressure law (an isobaric process).

Mathematical Formulation and Its Interpretation

For a gas that is enclosed in a cylinder, having volume V and absolute temperature T at constant temperature T, Charles’s Law can be written as:

V ∝ T

V = (constant) × T

V = k × T

V/T = k

Let us assume that before expansion, the initial volume and temperature of the gas were V₁ and T_1, and after expansion, the final volume and temperature were V₂ and T₂. In that case, the last equation can be written as:

V₁ / T₁ = k

V₂ / T₂ = k

Equating the two equations gives:

V₁ / T₁ = V₂ / T₂

It is evident from the above equation that for an ideal gas, the ratio of the initial volume and temperature of the gas and the ratio of its final volume and temperature are the same, given that its pressure remains constant.

In other words, the equation shows that volume and temperature are directly interconnected. It means that whenever there is an increase in temperature, there will be a corresponding increase in volume, and vice versa.

Significance of Charles’s Law

Charles’s Law gives valuable comprehension of volume and pressure. It is found in action in many real-world applications, e.g., healthcare, scientific research, industrial activities, engineering applications, etc.

Real-World Applications and Examples

Hot Air Balloons

Hot air balloons ascend from the ground because the heated air inside them is less dense than the surrounding air. Charles’s Law helps us understand this phenomenon:

When the air inside the balloon is heated, its volume expands, making it less dense compared to the cooler air outside. This buoyant force generated by the lighter air causes the balloon to rise.

Conversely, when the heating process ceases, the air inside the balloon cools down, causing its volume to decrease and become denser. As a result, the hot air balloon descends back to the ground.

Thermometers

Gas thermometers are precise instruments used to measure temperature, operating based on Charles’s Law. When the temperature rises, the gas inside the bulb expands, increasing its pressure. This pressure change is transmitted to a liquid-filled manometer, causing the liquid level to rise. The rise in the liquid level is then correlated to the temperature using a known scale or calibration.

Conversely, when the temperature decreases, the gas contracts, leading to a decrease in pressure. This decrease in pressure is reflected as a lower reading on the measuring device. Therefore, the movement of the liquid (such as mercury or alcohol) in the manometer indicates a temperature change.

Gay-Lussac’s Law

Gay–Lussac’s Law, or Amontons’s Law, is the same name in thermodynamics. It is one of the fundamental gas laws, most commonly known as Gay–Lussac’s Law, and named after Joseph Louis Gay–Lussac who was a French chemist. This law states that:

For a certain amount of an ideal gas present in a cylinder, the pressure is directly proportional to the absolute temperature, given that volume remains constant.

Charles’s Law is also known as the constant volume law (an isochoric process).

Mathematical Formulation and Its Interpretation

For a gas that is enclosed in a cylinder, having pressure P and absolute temperature T at a constant volume V, Gay–Lussac’s Law can be written as:

P ∝ T

P = (constant) × T

P = k × T

P/T = k

Let us assume that before expansion, the initial pressure and temperature of the gas were P₁ and T_1, and after expansion, the final pressure and volume were P₂ and T₂. In that case, the last equation can be written as:

P₁ / T₁ = k

P₂ / T₂ = k

Equating the two equations gives:

P₁ / T₁ = P₂ / T₂

It is evident from the above equation that for an ideal gas, the ratio of the initial pressure and temperature of the gas and the ratio of its final pressure and temperature are the same, given that its volume remains constant.

In other words, the equation shows that pressure and temperature are directly interconnected. It means that whenever there is an increase in temperature, there will be a corresponding increase in pressure, and vice versa.

Significance of Gay-Lussac’s Law

Gay-Lussac’s Law holds significant importance across various fields, including chemistry, manufacturing, meteorology, industries, and engineering. Scientists, researchers, and engineers utilize this gas law in real-time applications to gain valuable insights into the relationship between the pressure and temperature of gases.

Real-World Applications and Examples

Pressure Cookers

Pressure cookers serve as an excellent example of Gay–Lussac’s Law within our homes. During cooking, steam is trapped inside the pressure cooker (constant volume process) while it is being heated. This trapped steam increases the inside temperature of the cooker, and consequently, the pressure inside the cooker rises correspondingly, leading to faster cooking.

Internal Combustion (IC) Engines

IC engines provide another example of Gay–Lussac’s Law in action. During the compression stroke, as the air-fuel mixture is fully compressed (higher pressure) inside the cylinder, its temperature rises as per the constant volume law.

This increase in temperature is essential for promoting an efficient combustion process and ensuring optimal engine performance.

Aerosol Cans

Aerosol cans operate based on the constant volume principle. These cans contain propellant gases under high pressure, along with the product liquid.

When the valve (actuator) is opened or pressed, the release of pressurised propellant gases forces the product liquid to expand and exit the can via a dip tube, forming a fine mist. This expansion of the liquid happens along with a drop in temperature, resulting in the cooling effect observed when using aerosol products.

Gas Cylinders

The engineering of gas cylinders is of utmost importance, and one fundamental source considered in their design is the principle of constant volume. This law states that the increase in pressure inside the cylinder is directly proportional to the temperature it experiences.

Meteorology

In meteorology, meteorologists analyse atmospheric conditions and forecast weather patterns using various principles, one of which is the law of constant volume. This principle recognizes that as altitude changes, it leads to variations in air pressure and, consequently, temperature.

These changes in temperature and pressure affect wind patterns, which are crucial factors in weather forecasting.

Avogadro’s Law

Avogadro’s Law, or Avogadro’s Principle, is the same name in thermodynamics. It is one of the fundamental gas laws, most commonly known as Avogadro’s Law, and named after Amedeo Avogadro, who was an Italian scientist. This law states that:

For an ideal gas present in a cylinder, the volume is directly proportional to the number of moles (also called the amount of substance), given that pressure and temperature remain constant.

Mathematical Formulation and Its Interpretation

For a gas that is enclosed in a cylinder, having volume V and the number of moles n at constant pressure P and temperature T, Avogadro’s Law can be written as:

V ∝ n

V = (constant) × n

V = k × n

V/n = k

Let us assume, before any changes, that the initial volume and number of moles of a gas were V₁ and n₁, and, after a certain process, the final volume and number of moles were V₂ and n₂. In that case, the last equation can be written as:

V₁ / n₁ = k

V₂ / n₂ = k

Equating the two equations gives:

V₁ / n₁ = V₂ / n₂

It is evident from the above equation that for an ideal gas, the ratio of the initial volume and number of moles of the gas and the ratio of its final volume and number of moles are the same, given that its pressure and temperature remain constant.

In other words, the equation shows that the volume and number of moles are directly interconnected. It means that whenever there is an increase in the number of moles of a gas, there will be a corresponding increase in volume, and vice versa.

Significance of Avogadro’s Law

For scientists and engineers, Avogadro’s Law was like a blessing to predict and manipulate gas behaviour in practical scenarios such as chemistry, physics, engineering, etc. The reason is that it provides valuable insights into chemical reactions and stoichiometry.

It also provides a crucial link between the macroscopic properties, like volume, and the microscopic properties, like the number of molecules in a gas.

Real-World Applications and Examples

Gas Storage

Regardless of its type, e.g., small-sized molecules like hydrogen (H₂) or comparatively larger molecules like oxygen (O₂), 1 mole of any gas occupies the same volume of 22.414 dm³ in a cylinder. Thus, Avogadro’s Law becomes relevant in our real-world applications.

Chemical Reactions

Stoichiometry is the quantitative study of a chemical reaction that tells how reactants and products are related to each other in terms of the number of moles involved. Avogadro’s Law is important in the stoichiometry calculation of gases.

For example, 1 mole of carbon (C) consumes (reacts with) 1 mole of oxygen (O₂) when they undergo a chemical change.

C          +          O₂        →     CO₂

Avogadro’s law directly applies to gases, as mentioned earlier. However, it can also be applied to reactions involving liquids and solids under certain conditions.

For liquids, this may involve ensuring the liquid is at its boiling point or close to it, where vapour pressure is significant, or at high temperatures where the liquid approaches ideal behaviour. For solids, high temperatures and low pressures may be necessary to allow sublimation or vaporisation to occur, again leading to behaviour akin to that of gases.

In essence, the conditions aim to minimize the effects of intermolecular forces so that the substances behave more like ideal gases, allowing Avogadro’s law to be applied effectively.

Gas Mixtures

Consider helium (He) and nitrogen (N₂). Both are inert gases and are enclosed in separate containers that are connected. For 1 mole of each gas at standard temperature and pressure (STP), the volume occupied would be 22.414 dm³.

As we allow the gases to mix, their total volume doubles, as does the number of moles. Thus, Avogadro’s Law plays a role in the mixture of gases at STP. 

The Ideal Gas Law

To find out details about the ideal gas law, click here.

Conclusion

We have seen the mesmerising world of gas laws and the way they become significant in our understanding of thermodynamics. We saw how the fundamental gas laws relate to pressure, volume, temperature, and moles of gas.

These laws provide awareness about the behaviour of gases and guide us in designing the operations of various systems and processes. These laws are the theoretical models to accurately measure pressure, volume, temperature, and moles of gas and validate them through practical models.

To understand the language of thermodynamics—its terminologies, concepts, etc.—it is important that we learn about these laws and see their relevance in our daily lives.

I encourage further exploration and study of these laws and their applications to deepen the understanding of thermodynamics and crack new possibilities for innovation and discovery.

Frequently Asked Questions (FAQs)

What are the 5 gas laws in physics?

The five gas laws in physics are Boyle’s Law, Charles’s Law, Avogadro’s Law, Gay-Lussac’s Law, and the Ideal Gas Law.

Write the names of notable scientists associated with the development of gas laws.

Notable scientists include Robert Boyle, Jacques Charles, Joseph Louis Gay-Lussac, and Amedeo Avogadro.

How did scientists historically contribute to the development of gas laws?

Through experimentation, the early scientists, namely Robert Boyle, Jacques Charles, and Joseph Louis Gay-Lussac, laid the foundation for gas laws. These discoveries led to the formulation of principles that describe behaviour of gases.

Write some real-world applications of Boyle’s Law.

Boyle’s Law can be seen in action in scuba diving, soda cans and bottles, and pneumatic systems (compressed air tools).

Enlist some practical applications of Charles’s Law.

Practical applications of Charles’s Law include hot air balloons and gas thermometers.

How does Avogadro’s Law help us understand gas behaviour?

Avogadro’s Law tells us about the relationship between gas volume and the number of gas molecules and thus enhances our understanding of gas density, products and reactants involved in a chemical reaction, and the behaviour of gas mixtures enclosed in a cylinder.

Why are gas laws essential in various scientific disciplines and industries?

Gas laws help in designing thermodynamic systems, analysing chemical reactions, and studying atmospheric phenomena. They play crucial roles in fields such as physics, chemistry, engineering, and environmental science.

What are some safety considerations related to gas storage based on gas laws?

Understanding gas laws helps ensure the safe storage of compressed gases, considering factors like pressure, temperature, and volume changes. Proper ventilation, pressure relief mechanisms, and adherence to storage guidelines are essential for safety.