Grade 10
  1. Matter and its properties  1.1. States of matter  1.2. Physical and chemical properties of matter  1.3. Classification of substances (elements, compounds, mixtures)  1.4. Changes in Matter (Physical and Chemical Changes)  1.5. Law of conservation of mass and law of definite proportions
  2. Atomic Structure  2.1. Historical development of the atomic model  2.2. Subatomic particles (protons, neutrons, electrons)  2.3. Atomic number, mass number and isotopes  2.4. Electronic Configuration and Energy Levels  2.5. Valency, ion formation and oxidation state
  3. Periodic table  3.1. History and Development of the Periodic Table  3.2. Modern Periodic Law and Periodic Trends  3.3. Groups and Periods in the Periodic Table  3.4. Trends in the Periodic Table  3.5. Metals, non-metals, metalloids and their properties  3.6. Noble gases and their chemical inertness
  4. Chemical bond  4.1. Formation of Chemical Bonds (Octet Rule)  4.2. Ionic Bonding and Properties of Ionic Compounds  4.3. Covalent Bond and Properties of Covalent Compounds  4.4. Metallic bond and its properties  4.5. Molecular geometry and VSEPR theory  4.6. Polarity and dipole moment of molecules  4.7. Intermolecular forces
  5. Chemical Reactions and Equations  5.1. Types of Chemical Reactions  5.2. Writing and balancing chemical equations  5.3. Law of conservation of mass in chemical reactions  5.4. Factors Affecting Chemical Reactions  5.5. Catalysts and their role in chemical reactions  5.6. Exothermic and Endothermic Reactions
  6. Stoichiometry and Chemical Calculations  6.1. Mole concept and Avogadro number  6.2. Molar Mass and Gram-Mole Conversions  6.3. Empirical and molecular formula  6.4. Stoichiometric calculations and chemical yield  6.5. Limiting and Excess Reactants
  7. Acids, Bases and Salts  7.1. Properties and Definitions of Acids and Bases (Arrhenius, Bronsted-Lowry, Lewis)  7.2. pH Scale, pOH, and Indicators  7.3. Neutralization reactions and salt formation  7.4. Strength of Acids and Bases (Strong vs. Weak Acids and Bases)  7.5. Common Acids and Bases in Daily Life  7.6. Salts, their solubility and applications
  8. Metals and Nonmetals  8.1. Physical and chemical properties of metals  8.2. Physical and Chemical Properties of Non-Metals  8.3. Reactivity Series of Metals and Displacement Reactions  8.4. Extraction of metals from ores  8.5. Corrosion, its causes and prevention  8.6. Alloys, their composition and uses
  9. Carbon and its compounds  9.1. Allotropes of Carbon  9.2. Hydrocarbons and their classification (alkanes, alkenes, alkynes)  9.3. Functional groups in organic compounds  9.4. Nomenclature of organic compounds (IUPAC system)  9.5. Isomerism in organic chemistry (structural and geometrical)  9.6. Important organic reactions (combustion, addition, substitution, polymerization)  9.7. Applications of organic compounds in industry and daily life
  10. Environmental Chemistry  10.1. Air Pollution (Sources, Effects and Control)  10.2. Water Pollution (Causes, Effects and Remedies)  10.3. Greenhouse effect and global warming  10.4. Ozone layer depletion and its effects  10.5. Green Chemistry and Its Applications  10.6. sustainable chemistry practice
  11. Thermochemistry  11.1. Heat and Energy Changes in Chemical Reactions  11.2. Exothermic and Endothermic Reactions  11.3. Enthalpy, enthalpy change, and heat of reaction  11.4. Specific heat capacity and calorimetry  11.5. Energy Changes in Combustion Reactions
  12. Electrochemistry  12.1. Electrolytes and non-electrolytes  12.2. Electrolysis and its applications (electroplating, extraction of metals)  12.3. Redox reactions (oxidation and reduction)  12.4. Galvanic cell and electrochemical series  12.5. Corrosion and electrochemical prevention methods
  13. Chemical kinetics and equilibrium  13.1. Rate of chemical reactions and its measurement  13.2. Factors affecting the reaction rate (catalyst, temperature, concentration)  13.3. Reversible and irreversible reactions  13.4. Dynamic equilibrium and equilibrium constant  13.5. Le Chatelier's principle and its applications
  14. Gases and Gas Laws  14.1. Properties of gases and kinetic molecular theory  14.2. Boyle's Law (Pressure-Volume Relation)  14.3. Charles's Law  14.4. Gay-Lussac's Law  14.5. Combined Gas Law and Ideal Gas Law  14.6. Real Gases vs Ideal Gases
  15. Nuclear Chemistry  15.1. Introduction to Radioactivity and Nuclear Reactions  15.2. Types of radioactive decay (alpha, beta, gamma)  15.3. Half-life and applications of radioactive isotopes  15.4. Nuclear fission and fusion reactions  15.5. Nuclear power generation and its environmental impact

Grade 10 → Gases and Gas Laws ↓


Gay-Lussac's Law


Gay-Lussac's law is an important concept in the study of gases and their interactions with temperature and pressure. French chemist Joseph Louis Gay-Lussac discovered this relationship in the early 19th century. Gay-Lussac's law is one of the laws of gases that explains the behavior of gases under different conditions. In simple terms, it states that the pressure of a gas is proportional to its absolute temperature when its volume is kept constant.

Understanding Gay-Lussac's law

The formula for Gay-Lussac's law can be expressed mathematically as follows:

P1 / T1 = P2 / T2

In this equation:

  • P1 and P2 represent the initial and final pressure of the gas, respectively.
  • T1 and T2 represent the initial and final absolute temperatures of the gas, respectively. (Remember, temperatures should always be in Kelvin.)

How to convert Celsius to Kelvin

Since Gay-Lussac's law expresses temperature in Kelvin, if you have a temperature in Celsius, you'll need to convert it to Kelvin. Here's how you can convert Celsius to Kelvin:

Kelvin = Celsius + 273.15

Visualizing the law

Let's understand Gay-Lussac's law with a simple example. Imagine you have a container filled with gas, and this container cannot change in shape (constant volume). Here is a simple SVG example to make the concept clear:

P1, T1 P2, T2

This example shows a gas at initial pressure P1 and temperature T1. As you apply heat, the temperature increases to T2, resulting in an increase in pressure to P2, showing the direct relationship between pressure and temperature.

Examples of Gay-Lussac's law in real life

Example 1: Pressure cooker

Pressure cookers are everyday appliances that demonstrate Gay-Lussac's law. Inside a sealed pressure cooker, as the contents heat up, the pressure increases. This happens because the temperature increases, and according to Gay-Lussac's law, the pressure must also increase if the volume remains constant.

Example 2: Aerosol can

Aerosol cans are another practical example. When the can is exposed to heat, the temperature of the gas inside the can increases. If there is no change in volume, the pressure inside will increase, sometimes causing the can to explode if the pressure exceeds the limits of the can.

Example 3: Car tires

In summer, car tires can be overinflated because the air inside the tire heats up, increasing the internal pressure. This shows the direct relationship between temperature and pressure in an enclosed space like a tire.

Deriving Gay-Lussac's law

Let us derive Gay-Lussac's law using basic principles. Consider a gas in two different situations. Initially, it has pressure P1 at temperature T1. After heating, assume that the pressure changes to P2 and the temperature changes to T2.

Mathematically, we start with the general ideal gas law:

PV = nRT

For constant volume and number of moles:

P1V = nRT1
P2V = nRT2

When we divide these two equations:

(P1V) / (P2V) = (nRT1) / (nRT2)

On simplifying, we get:

P1 / P2 = T1 / T2

By rearranging we get the general form of Gay-Lussac's law:

P1 / T1 = P2 / T2

Limitations of Gay-Lussac's law

Gay-Lussac's law is true under the assumption that the gas behaves ideally, and the volume is constant. However, it is important to note several limitations:

  1. Real gases do not follow this law closely at high pressures and low temperatures, because there they deviate from ideal behaviour.
  2. For the law to apply, the container must be rigid, and there must be no change in its volume.
  3. If the gas undergoes a phase change, such as condensing into a liquid, this law does not apply because its volume does not remain constant.

Practice problems

Problem 1

The pressure of a gas is 101 kPa and the temperature is 300 K. If the temperature is increased to 350 K, what will be the new pressure assuming the volume to be constant?

Solution

Applying Gay-Lussac's law:

P1 / T1 = P2 / T2
  • P1 = 101 kPa
  • T1 = 300 K
  • T2 = 350 K

Substitute the known values:

101 / 300 = P2 / 350

Solving for P2 gives:

P2 = (101 * 350) / 300 = 118.17 kPa

The new pressure is 118.17 kPa.

Problem 2

If 500 ml of a gas is at 2 atm pressure and 273 K, and you change the temperature to 373 K, find the new pressure of the gas (assuming the volume remains constant).

Solution

Again, use Gay-Lussac's law:

P1 / T1 = P2 / T2
  • P1 = 2 atm
  • T1 = 273 K
  • T2 = 373 K

Insert the values into the equation:

2 / 273 = P2 / 373

Solve for P2:

P2 = (2 * 373) / 273 = 2.73 atm

The new pressure is 2.73 atm.

Conclusion

Gay-Lussac's law is a fundamental gas law that describes the relationship between the pressure and temperature of a gas, provided the volume remains constant. It helps us understand how gases behave under different thermal conditions and is important for applications ranging from simple household appliances to complex industrial processes. By recognizing this relationship, we can safely control and predict gas behavior in everyday and scientific contexts.


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Charles's Law
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Combined Gas Law and Ideal Gas Law

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Gay-Lussac's Law

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