Grade 8
  1. Introduction to Chemistry  1.1. Nature and scope of chemistry  1.2. Importance of chemistry in daily life  1.3. Chemistry and its relation with other sciences  1.4. The role of chemistry in industry, medicine and the environment  1.5. Scientific investigation and experimental methods in chemistry
  2. Matter and its properties  2.1. Definition and classification of matter  2.2. Physical and chemical properties of matter  2.3. Law of conservation of matter  2.4. Extensive and Intensive Properties of Matter  2.5. Kinetic molecular theory of matter  2.6. States of matter: solids, liquids, gases, plasmas, and Bose-Einstein condensates  2.7. Changes in state and energy are involved  2.8. Diffusion and Brownian motion
  3. Elements, Compounds, and Mixtures  3.1. Definition and differences between elements, compounds, and mixtures  3.2. Atomic Structure and Atomic Number  3.3. Chemical symbols and formulas  3.4. Trends in the Periodic Table (Groups and Periods)  3.5. Classification of Elements: Metals, Nonmetals and Metalloids  3.6. Rare Earth Elements and Transition Metals  3.7. Types of mixtures: homogeneous and heterogeneous  3.8. Separation of Mixtures Using Physical and Chemical Methods
  4. Separation Techniques  4.1. Filtration, Sedimentation and Decantation  4.2. Evaporation and crystallization  4.3. Distillation and Fractional Distillation  4.4. Chromatography and its applications  4.5. Sublimation in the purification of compounds  4.6. The role of centrifugation in biochemical processes
  5. Atomic Structure  5.1. Dalton's atomic theory  5.2. Structure of the atom: protons, neutrons and electrons  5.3. Bohr's atomic model  5.4. Introduction to Quantum Mechanical Model  5.5. Electron Configuration and Energy Levels  5.6. Excitation and emission spectra  5.7. Isotopes and their applications
  6. Periodic Table and Chemical Trends  6.1. History and Development of the Periodic Table  6.2. Modern periodic law  6.3. Periodicity and trends in atomic and ionic sizes  6.4. Ionization Energy, Electron Affinity and Electronegativity  6.5. Introduction to Lanthanides and Actinides  6.6. Application of periodic trends in chemistry
  7. Chemical Bonding and Molecular Structure  7.1. Types of chemical bonds: ionic, covalent and metallic bonds  7.3. Polar and Nonpolar Molecules  7.4. Hydrogen bonding and its applications  7.5. Intermolecular forces: dipole-dipole, London dispersion force
  8. Chemical Reactions and Stoichiometry  8.1. Chemical Equations and Balance  8.2. Types of Chemical Reactions: Combination, Decomposition, Displacement and Redox  8.3. Introduction to stoichiometry and the mole concept  8.4. Limiting reactant in chemical equations  8.5. Reaction rate, catalyst, and factors affecting reaction rate
  9. Acids, Bases and Salts  9.1. Definition and Properties of Acids and Bases  9.2. Strong vs. Weak Acids and Bases  9.3. pH Scale and pH Calculation  9.4. Neutralization reactions  9.5. Buffer solutions and their importance  9.6. Applications of Acids, Bases and Salts in Daily Life
  10. Solutions and Solubility  10.1. Definition of Solution, Solute, and Solvent  10.2. Factors Affecting Solubility  10.3. Concentration units: molarity and molality  10.4. Saturated, unsaturated and supersaturated solutions  10.5. Concept of osmosis and reverse osmosis  10.6. Concentrative properties of solutions
  11. Gases and Gas Laws  11.1. Properties of gases  11.2. Introduction to Ideal and Real Gases  11.3. Boyle's Law, Charles' Law and Avogadro's Law  11.4. Ideal Gas Equation and Its Applications  11.5. Application of Gas Laws in Real Life
  12. Thermochemistry and energy transformation  12.1. Energy in Chemical Reactions  12.2. Exothermic vs. Endothermic Reactions  12.3. Heat and Enthalpy Changes  12.4. Calorimetry and heat transfer in reactions
  13. Metals and Nonmetals  13.1. Physical and Chemical Properties of Metals and Nonmetals  13.2. Reactivity Series of Metals  13.3. Corrosion and its prevention  13.4. Extraction of metals from ores  13.5. Uses of metals and non-metals in daily life
  14. Introduction to Organic Chemistry  14.1. Characteristics of carbon and organic compounds  14.2. Functional groups and their importance  14.3. Simple Hydrocarbons: Alkenes, Alkenes and Alkynes  14.4. Isomerism in organic compounds  14.5. Introduction to polymers and their uses
  15. Environmental Chemistry and Sustainability  15.1. Green Chemistry Principles  15.2. Effects of Chemical Pollution on Ecosystems  15.3. Acid rain and its effects  15.4. Ozone layer depletion and global warming  15.5. Waste Management and Recycling in Chemistry

Grade 8 → Gases and Gas Laws ↓


Boyle's Law, Charles' Law and Avogadro's Law


Gases are fascinating because they behave in a way that can be predicted using simple rules. Three of these important laws are Boyle's Law, Charles' Law, and Avogadro's Law. These laws describe how gases behave under different conditions of pressure, volume, and temperature. In this guide, we will go over each of these laws in detail with simple language and visual examples so you can understand them better.

Boyle's law

Boyle's law is about the relationship between pressure and volume when the temperature is kept constant. This law is named after Robert Boyle, who discovered it in the 17th century. According to Boyle's law, if you have a sample of gas and you keep its temperature constant, the volume of the gas is inversely proportional to its pressure. This means that as the pressure on the gas increases, the volume of the gas decreases and vice versa.

P1 * V1 = P2 * V2

The meaning of this equation is as follows:

  • P1 is the initial pressure of the gas.
  • V1 is the initial volume of the gas.
  • P2 is the final pressure of the gas.
  • V2 is the final volume of the gas.

Visual example

Imagine you have a balloon:

low pressure, high volume

Now, if you press the balloon:

high pressure, low volume

This illustration shows that as pressure increases (squeezing the balloon), the volume decreases.

Text example

Consider a closed, flexible container filled with air. If you apply pressure to the container, thereby reducing its volume, you are increasing the pressure inside the container. According to Boyle's law, pressure multiplied by volume remains constant (assuming the temperature is constant). If the initial conditions are 2 liters and a pressure of 1 atmosphere, compressing the container by 1 liter doubles the pressure to 2 atmospheres.

Charles's law

Charles' law describes how gases expand when heated. It states that the volume of a gas is directly proportional to its temperature when the pressure is constant. The law is named after Jacques Charles who discovered it in the 1780s.

V1 / T1 = V2 / T2

The meaning of this equation is this:

  • V1 is the initial volume of the gas.
  • T1 is the initial temperature of the gas (in Kelvin).
  • V2 is the final volume of the gas.
  • T2 is the final temperature of the gas (in Kelvin).

Visual example

Imagine a hot air balloon:

High temperature, large volume

As the air inside the balloon heats up, the balloon expands.

Text example

Suppose you have a piston containing a 300 Kelvin gas that occupies a volume of 1 liter. If you raise the temperature of the gas to 600 Kelvin while keeping the pressure constant, according to Charles's law, the volume will increase to accommodate the increase in temperature, resulting in a new volume of 2 liters.

Avogadro's law

Avogadro's law states that the volume of a gas at constant temperature and pressure is directly proportional to the number of moles of the gas. This means that increasing the number of gas molecules will increase the volume, provided there is no change in temperature and pressure. This law was named after Amedeo Avogadro.

V1 / n1 = V2 / n2

The meaning of this equation is this:

  • V1 is the initial volume of the gas.
  • n1 is the initial number of moles of gas.
  • V2 is the final volume of the gas.
  • n2 is the final number of moles of the gas.

Visual example

Imagine the balloon once again, this time with molecules:

More molecules, larger volume

Putting more air (gas molecules) into the balloon causes it to expand.

Text example

If you have a syringe filled with 1 liter of gas, and you put another mole of the same gas into the syringe while keeping the temperature and pressure constant, according to Avogadro's law, the volume will increase by 2 liters.

Conclusion

Understanding the behavior of gases is important to understanding many natural phenomena and technological processes. Boyle's law helps us understand how pressure and volume are related. Charles' law shows how volume changes with temperature. Avogadro's law explains the relationship between volume and the amount of a gas. Together, these laws provide a comprehensive understanding of how gases behave under different conditions, and they form the basis for more advanced studies in chemistry and physics.

These gas laws are essential tools for scientists and are also used in a variety of applications, such as ballooning, scuba diving, and even in our understanding of the atmosphere and weather systems. Understanding these fundamental concepts gives students the knowledge to explore more complex chemical reactions and interactions in their future studies.


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Introduction to Ideal and Real Gases
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Boyle's Law, Charles' Law and Avogadro's Law

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