Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → Carbon and its compounds → Hydrocarbons ↓


Alkene


Alkanes are a fascinating group of hydrocarbons that students encounter in chemistry, especially when studying organic compounds. They are unsaturated hydrocarbons, which means that they contain at least one carbon-carbon double bond in their chemical structure. This double bond distinguishes alkanes from alkenes, which have only single bonds between carbon atoms.

Understanding the basics of alkenes

The simplest alkene is ethene, with the chemical formula C 2 H 4. Understanding ethene is important in understanding what makes alkenes unique. The structure of ethene looks like this:

      HH
       ,
        C = C
       ,
      HH

In this structure, two carbon atoms are connected by a double bond. This double bond is made up of a sigma bond and a pi bond. Hydrogen atoms are bonded to the carbon atoms via single bonds.

Properties of alkenes

Alkenes have a number of special properties due to the presence of the double bond:

  • Unsaturation: The double bond makes alkenes unsaturated. This unsaturation makes them more reactive than alkenes, especially in addition reactions.
  • Physical state: At room temperature, lower alkenes such as ethene and propene are gases, while higher alkenes (those with longer carbon chains) can be liquids or solids.
  • Solubility: Alkenes are generally insoluble in water but are soluble in organic solvents due to their nonpolar nature.
  • Boiling point and melting point: As the length of the carbon chain in alkenes increases, their boiling point and melting point increase due to increase in van der Waals forces.

Nomenclature of alkenes

The naming of alkanes follows certain rules set by the International Union of Pure and Applied Chemistry (IUPAC). Here is a simple guide to naming alkanes:

  1. Identify the longest carbon chain that contains a double bond. This chain will determine the base name of the alkene.
  2. Number the carbon chain from the end closest to the double bond.
  3. Indicate the position of the double bond with the lowest possible number. For example, in but-1-ene, '1' indicates the double bond starting at the first carbon.
  4. Use appropriate prefixes for additional substituents or branches on the main chain.

Examples of alkenes and their IUPAC names include:

  • Ethene (C 2 H 4)
  • Propane (C 3 H 6)
  • But-1-ene (C 4 H 8)
  • But-2-ene (C 4 H 8)

Example of but-2-ene

Consider the structure and position of the double bonds in but-2-ene:

      hhhh
       ,
        C - C
       ,
      HC = C – CH
          ,
          haha

Chemical reactions of alkenes

Alkenes are very reactive because of the double bond. Here are some common reactions:

Addition reactions

Alkenes readily participate in addition reactions, where atoms add across a carbon-carbon double bond, converting it into a single bond.

Hydrogenation

The addition of hydrogen (H2) converts the alkene to an alkane:

      C 2 H 4 + H 2 → C 2 H 6

Halogenation

Addition of halogens such as chlorine (Cl2) or bromine (Br2):

      C 2 H 4 + Cl 2 → C 2 H 4 Cl 2

Hydration

Alcohol is formed by adding water (H 2 O) in the presence of an acidic catalyst:

      C 2 H 4 + H 2 O → C 2 H 5 OH

Polymerization

Alkenes can undergo polymerization, a process that joins smaller molecules to form long chains called polymers. The polymerization of ethene produces polyethylene, a common plastic material.

Polymerization of ethene:

      N C 2 H 4 → -(-CH 2 -CH 2 -)- N

Geometrical isomerism in alkenes

Another interesting feature of alkenes is geometric isomerism, which arises due to restricted rotation around the carbon-carbon double bond. This leads to different spatial arrangements of the groups, called "cis" and "trans" isomers.

Cis-trans isomerism

Take the example of but-2-ene:

Cis-isomers: identical groups are on the same side.

      HH
       ,
        C = C
       ,
      CH 3 CH 3

Trans-isomers: identical groups are in opposite directions.

      H CH 3
       ,
        C = C
       ,
      CH 3 H

Importance and uses of alkenes

Alkenes are important in a variety of industrial applications:

  • Ethene is used in the production of ethanol, polyethylene, and ethylene oxide.
  • Propene is a key raw material in the production of polypropylene.
  • Alkenes are also used in the production of detergents and plastics.

Conclusion

Alkanes are an important class of organic compounds, characterized by their carbon-carbon double bonds. Through understanding alkanes, including their structure, reactions, and applications, one gains a broader insight into the field of organic chemistry. By learning about alkanes, students can begin to appreciate the richness and complexity of chemical compounds and their applications in everyday life.


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Alkene

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