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 ↓


Charles's Law


In Class 10 Chemistry, one of the fundamental concepts you will learn is the behaviour of gases and the various gas laws. Charles' Law is one of these essential principles, which enhances our understanding of the behaviour of gases under various conditions. Whether you are filling a balloon or considering how an air conditioning system works, Charles' Law plays a vital role. This article discusses Charles' Law in depth, exploring its intricacies through easy-to-understand language, textual examples, and visual demonstrations to enhance your understanding.

What is Charles's law?

Charles' law describes the direct relationship between the temperature and volume of a gas, assuming that the pressure and the quantity of the gas remain constant. Simply put, if you increase the temperature of a gas, its volume will increase; similarly, if you decrease the temperature, the volume will decrease. This behavior occurs because at higher temperatures, gas particles move more rapidly, spread out and take up more space.

Charles's law formula

The mathematical expression of Charles's law is:

V1/T1 = V2/T2

Where:

  • V1 is the initial volume.
  • T1 is the initial temperature (expressed in Kelvin).
  • V2 is the last section.
  • T2 is the final temperature (expressed in Kelvin).

Understanding the law through a simple experiment

Imagine you have a balloon. Initially, the balloon is kept at room temperature. Now, if you place the balloon in a warmer environment, the balloon expands. Conversely, if you place the balloon in a colder environment, it contracts. This change occurs because the heat from the environment transfers more energy to the gas particles in your balloon, causing them to move more rapidly and occupy a greater amount of space.

Conversely, when the temperature decreases, the kinetic energy of the gas particles decreases, causing them to occupy less space. Therefore, explaining this phenomenon supports Charles' law which shows a direct relationship between temperature and the volume of a gas.

Applying Charles's law: Text examples and calculations

Example 1: Expanding air

Let's consider an example where you have 5 liters of gas at 300 K. If the temperature is increased to 350 K while keeping the pressure constant, what will be its volume?

Using Charles's law, we get:

      
V1 = 5 liters
T1 = 300 K
T2 = 350 K
V2 = ?

V1/T1 = V2/T2
5 / 300 = V2 / 350
V2 = (5 * 350) / 300
V2 = 5.83 liters

So, the new quantity of gas will be 5.83 litres.

Example 2: Shrinking balloon

Suppose the volume of a balloon is 2 liters at 280 K. If the temperature is decreased to 230 K, what will be the new volume of the balloon?

      
V1 = 2 liters
T1 = 280 K
T2 = 230 K
V2 = ?

V1/T1 = V2/T2
2 / 280 = V2 / 230
V2 = (2 * 230) / 280
V2 = 1.64 liters

When the temperature decreases the new volume will be 1.64 litres.

Visualization of Charles' law

To understand Charles's law further, let's look at the relationship between temperature and volume with the help of a graph.

Temperature (K) Volume (L) V = T * k

In the graph above, the axes represent temperature and volume, respectively. From the line defined by the equation V = T * k (where k is a constant when pressure is constant) we can see that as the temperature increases, the volume also increases, which shows the direct relationship represented by Charles's law.

Real life applications of Charles' law

Charles's law can be observed in countless everyday situations:

1. Hot air balloons

Hot air balloons work on this principle. When the air inside the balloon heats up, it expands, causing the balloon to rise. The expansion of the air reduces its density relative to the cooler air outside the balloon, causing it to float.

2. Internal combustion engine

In engines, the combustion of fuel heats gases, which expand and exert pressure on the engine's pistons, producing motion.

3. Air conditioning and refrigeration

These systems use Charles's law in their thermal cycles to expand or compress gases to moderate temperatures in the atmosphere.

Key points to remember

  • Always use Kelvin for temperature when applying Charles's law.
  • As long as the pressure remains constant, volume and temperature are directly proportional.
  • Charles's law applies only to ideal gases, where no external forces act on the gas particles other than changes in pressure and temperature.

Frequently asked questions

Why should we use Kelvin temperature in Charles's law?

The Kelvin is used because it starts at absolute zero, meaning that zero on the Kelvin scale corresponds to the complete absence of thermal energy. This uniformity is necessary for accurate calculation of thermal behavior and correlations.

Can Charles's law be applied to liquids or solids?

No, Charles' law applies strictly to gases because their particle speeds and spacing are unique, which are directly related to changes in temperature and volume. Solids and liquids do not expand or contract in the same way.

Conclusion

Charles's law is a fundamental aspect of understanding gas behavior. It provides important information about how gases react to changes in temperature, providing utility in both theoretical applications and practical, everyday phenomena. Whether it's the rise of a hot air balloon or the working of a refrigerator, the principles underlying Charles's law resonate across many layers of scientific study and technological innovation.


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Boyle's Law (Pressure-Volume Relation)
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Gay-Lussac's Law

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Charles's Law

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