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 ↓


Introduction to Ideal and Real Gases


Gases are an integral part of our daily lives. We breathe air, which is a mixture of gases. Weather balloons rise because of the gases they contain. Even soft drinks fizz because of gases. In this article, we will explore the concept of gases in chemistry, focusing on the difference between ideal and real gases.

What are gases?

Basically, a gas is a state of matter that has neither a definite shape nor a definite volume. This means that gases can expand to fill any container. The molecules in gases are much more spread out than those in liquids and solids, and this is what gives gases their unique properties.

Properties of gases

Gases have some distinctive properties:

  • They're compressible: you can squeeze gases into smaller volumes.
  • They expand to fill their containers: gases expand evenly throughout the container, regardless of the container's size or shape.
  • They mix uniformly and completely: Different gases can mix together uniformly without any obstructions.
  • They exert pressure: Gas molecules collide with the walls of their container, creating pressure.

The concept of ideal gases

To better understand gases, scientists use the concept of an "ideal gas." An ideal gas is a theoretical gas composed of a set of randomly moving, non-interacting point particles. Ideal gases help scientists develop mathematical models to predict how gases behave under different conditions. For an ideal gas, they follow a set of rules known as the ideal gas laws.

Ideal Gas Law

The ideal gas law describes the relationship between pressure, volume, temperature, and number of moles of a gas. The basic formula for an ideal gas is expressed as:

PV = nRT

Where:

  • P is the pressure of the gas
  • V is the volume of the gas
  • n is the amount of gas in moles
  • R is the ideal gas constant
  • T is the temperature of the gas in Kelvin

Let us break these down further:

Pressure (P)

Pressure is the force that a gas exerts on the walls of its container. It is measured in units such as atmospheres (atm), pascals (Pa), or millimeters of mercury (mmHg).

Volume (V)

Volume is the space the gas occupies. Common units are liters (L) or cubic meters (m3).

Volume of gas (n)

The amount of gas is measured in moles, which is a way of expressing the amount of a substance based on the number of particles, usually atoms or molecules.

Temperature (T)

In chemistry, temperature is measured in Kelvin (K). To convert Celsius to Kelvin, add 273.15 to the Celsius temperature.

Ideal gas constant (R)

R is a constant that enables the units to work correctly. Its value depends on the units used for pressure and volume, but when pressure is in atm and volume in liters, it is often 0.0821 L atm/(K mol).

Visual Example: Ideal Gas Law

        /** * Ideal Gas Law Visualization * Variables are represented as circles with arrows indicating their interaction */
        /** * Ideal Gas Law Visualization * Variables are represented as circles with arrows indicating their interaction */
        
        
        P
        
        
        V
        
        
        T

Real gases

Unlike ideal gases, real gases do not always obey the ideal gas law, especially under conditions such as high pressure or low temperature. Real gases have molecules with volume and intermolecular forces, which can affect their behavior.

Difference between real and ideal gases

While ideal gases are a simple model and are very useful, they do not take into account all the complexities of real gases. Here are some key differences:

  • Volume of molecules: Molecules in real gases occupy space, while ideal gases are point particles without volume.
  • Intermolecular forces: Real gases have forces of attraction or repulsion between molecules, whereas ideal gases do not.
  • High pressure: At high pressure, real gases can deviate significantly from ideal gas behavior due to the volume and intermolecular forces of the molecules.
  • Low temperatures: At low temperatures, the kinetic energy of gas molecules decreases, making intermolecular forces more significant and producing deviations from ideal behaviour.

Van der Waals equation

The van der Waals equation modifies the ideal gas law by taking into account the volume and intermolecular forces of the gas molecules. It is written as:

[ P + a(n/V)^2 ] (V - nb) = nRT

Where:

  • a is a measure of the attraction between the particles.
  • b is the volume occupied by one mole of gas particles.

Visual example: real gas effect

        /** * Real Gas Effect * Showing molecules in a container with forces between them */
        /** * Real Gas Effect * Showing molecules in a container with forces between them */

Lesson example: How gases deviate from ideal behavior

Imagine that you are filling a balloon with air. Under normal conditions, air behaves very close to an ideal gas. However, if you take the balloon to a cold mountainous region, you can see that it shrinks. This happens because the real gas inside the balloon does not behave ideally at low temperatures.

Another example is the compressed natural gas used in vehicles. At high pressure, gas molecules come closer together, making the effect of their volume more noticeable, thus deviating from the ideal gas law.

Applications of gases

Understanding how gases work is important in several areas:

  • Weather forecasting: Meteorologists use the gas laws to forecast weather patterns and changes.
  • Engineering: Gas laws help in designing engines, refrigeration systems, and even space travel.
  • Medical applications: Gases such as oxygen and nitrous oxide are used in medical treatment and surgery.

Conclusion

Gases are fascinating and their study is essential to chemistry. By understanding the difference between ideal and real gases, as well as the laws that govern them, we gain valuable information about natural and industrial processes involving gases.


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Properties of gases
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Boyle's Law, Charles' Law and Avogadro's Law

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Introduction to Ideal and Real Gases

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