Allotropy or allotropism, refers to the ability of some chemical elements to exist in two or more different forms in the same physical state, known as allotropes. Allotropes are structural variations of an element in which the atoms are linked together in different manners. Carbon allotropes include diamond (carbon atoms bonded together to form a cubic lattice of tetrahedra), graphite (carbon atoms bonded together in sheets of a hexagonal lattice), graphene (single sheets of graphite), and fullerenes (carbon atoms bonded together in spherical, tubular, or ellipsoidal formations).
Topics
Chemical Reactions and Equations
- Chemical Reactions in Daily Life
- Chemical Equations
- Balancing Chemical Equation
- Types of Chemical Reactions > Combination Reaction
- Types of Chemical Reactions > Decomposition Reaction
- Types of Chemical Reactions > Single Displacement Reaction
- Types of Chemical Reactions > Double Displacement Reaction
- Chemical Properties of Carbon Compounds > Oxidation
- The Effects of Oxidation Reactions in Everyday Life
Acids, Bases and Salts
- Acids and Bases in Daily Life
- Acids and Bases in the Laboratory
- Acids and Bases React with Metals
- Reaction of Metal Carbonates with Acids
- Acids and Bases Reaction with each other
- Reaction of Metallic Oxides with Acids
- Reaction of a Non-metallic Oxide with Base
- Common Properties of Acids and Bases
- The pH Scale
- Importance of pH in Everyday Life
- Salts > Family of Salts
- Salts > pH of Salts
- Salts > Chemicals from Common Salt
- Salts > Water in Salt Crystals
Metals and Non-metals
Carbon and its Compounds
- Importance of Carbon
- The Covalent Bond
- Allotropes of Carbon > Diamond
- Allotropes of Carbon > Graphite
- Allotropes of Carbon > Fullerene
- Carbon: A Versatile Element
- Organic Compounds
- Classification of Hydrocarbons
- Carbon Compounds: Chains, Branches, Rings
- Homologous Series
- Nomenclature
- Chemical Properties of Carbon Compounds > Combustion
- Ethanol
- Ethanoic Acid
- Soaps and Detergents
Life Processes
- Life Processes in Living Organisms
- Nutrition
- Autotrophic Nutrition
- Heterotrophic Nutrition
- Nutrition in Human Beings
- Dental Caries
- Cellular Respiration
- Human Respiratory System
- Production of ATP
- Blood Circulatory System
- Human Heart
- Blood Vessels Entering and Leaving The Heart
- Valves of the Heart
- Blood Pressure (B.P.)
- Blood Vessels
- Composition of Blood > Cellular Elements: Blood Platelets (Thrombocytes)
- Tissue Fluid (Or Intercellular Fluid)
- Lymph and Lymphatic System
- Transportation in Plants
- Transportation of Water
- Transportation of Food and Other Substances
- Excretion
- Excretion in Human Beings
- Kidney and Its Internal Structure
- Structure of a Kidney Tubule (Nephrons)
- Dialysis and Artificial Kidney
- Excretion in Plants
- Organ and Body Donation
Control and Co-ordination
- Human Nervous System
- Neuron (Or Nerve Cell)
- Synapse
- Nerves
- Reflex Action
- Reflex Arc
- The Human Brain
- The Spinal Cord
- Mechanism of Muscle Action Under Nervous Control
- Coordination and Response to Stimuli in Plants
- Tropic Movements in Plants
- Phototropism
- Geotropism
- Hydrotropism
- Thigmotropism
- Chemotropism
- Hormonal Regulation in Animals
How do Organisms Reproduce?
Heredity
Light – Reflection and Refraction
- Light and Its Straight-Line Propagation
- Reflection of Light
- Spherical Mirrors
- Image Formation by Spherical Mirrors
- Representation of Images Formed by Spherical Mirrors
- Image Formation by Concave Mirror
- Image Formation by a Convex Mirror
- Sign Convention for Reflection by Spherical Mirrors
- Ray Optics - Mirror Formula
- Refraction of Light
- Refraction through a Rectangular Glass Slab
- The Refractive Index
- Refraction by Spherical Lenses
- Image Formation by Lenses
- Image Formation in Lenses Using Ray Diagrams
- Sign Convention for Spherical Lenses
- Lens Formula
- Power of a Lens
The Human Eye and the Colourful World
- The Human Eye
- Defects of Vision and Their Correction
- Defects of Vision and Their Corrections > Myopia
- Defects of Vision and Their Corrections > Hypermetropia
- Defects of Vision and Their Corrections > Presbyopia
- Refraction of Light Through a Prism
- Dispersion of Light
- Atmosphere Refraction
- Scattering of Light
Electricity
Magnetic Effects of Electric Current
- Magnetic Effect of Electric Current
- Applications of Biot-Savart's Law > Magnetic Field due to a Finite Straight Current-Carrying Wire
- Magnetic Field Due to a Current-Carrying Conductor
- Right-hand Thumb Rule
- Applications of Biot-Savart's Law > Magnetic Field at the Centre of a Circular Loop
- Applications of Ampere’s Circuital Law > Magnetic Field of a Long Straight Solenoid
- Force on a Current Carrying Conductor in a Magnetic Field
- Fleming’s Left Hand Rule
- Magnetism in Medicine
- Domestic Electric Circuits
Our Environment
- Crystalline Forms
- Diamond
- Uses of Diamond
Maharashtra State Board: Class 9
Crystalline Forms:
Crystalline forms of materials are substances in which the atoms are arranged in a regular, repeating pattern. This orderly structure gives crystalline forms unique properties, making them distinct from amorphous materials, which lack such arrangement. Crystalline substances are commonly found in nature and include materials like diamonds, graphite, and quartz.
- Crystalline forms have a well-organised and definite arrangement of atoms, ions, or molecules.
- The strong forces of attraction in their structured arrangement result in high melting and boiling points.
- Crystalline forms possess definite geometrical shapes with sharp edges and flat surfaces (planes).
- Due to their orderly structure, they often exhibit symmetry and may display different properties in different directions (anisotropy).
- Crystalline materials melt sharply at a specific temperature, distinguishing them from amorphous substances, which soften over a range.
Maharashtra State Board: Class 9
Allotropy:
Maharashtra State Board: Class 9
Diamond:
Diamonds have fascinated people throughout history for their beauty, rarity, and unique properties. Once renowned for the famous 'Kohinoor' diamond, India has been a prominent source of these precious gems, particularly in regions like Golconda and Panna. Diamonds are also found globally, in places such as South Africa, Brazil, and Russia. Their remarkable characteristics arise from their unique atomic structure, where each carbon atom is covalently bonded to four others in a three-dimensional arrangement, making diamonds incredibly hard.
Diamond
- Diamonds are the hardest natural substance, known for their exceptional durability and brilliance.
- The density of diamond is 3.5 g/cm³, reflecting its compact atomic structure.
- Diamonds have a very high melting point of 3500°C, making them resistant to extreme heat.
- When heated to 800°C in the presence of oxygen, diamonds release carbon dioxide without forming any other products.
- Diamonds do not dissolve in any solvent, showcasing their chemical stability.
- Acids and bases have no effect on diamonds, further highlighting their inert nature.
- Diamonds are poor conductors of electricity because they lack free electrons.
- These properties make diamonds valuable for industrial applications and prized as gemstones.
Structure of carbon atoms in diamond
Maharashtra State Board: Class 9
Uses of Diamond:
- Diamonds are used in glass-cutting and rock-drilling machines due to their exceptional hardness.
- They are widely used in making ornaments and jewellery for their brilliance and aesthetic appeal.
- Diamond knives are utilised in eye surgeries for precise and delicate procedures.
- Diamond dust is used to polish other diamonds, improving their shine and finish.
- Diamonds are used to create protective windows in space equipment and artificial satellites to shield against radiation.
- They are essential in industrial tools for grinding, cutting, and shaping hard materials.
- Diamonds are applied in heat sinks for electronics, efficiently dissipating heat due to their high thermal conductivity.
- They enhance sound quality in high-performance speakers by reducing distortion.
- Diamonds are used in advanced optical systems and lasers for their clarity and durability.
- Synthetic diamonds are increasingly being used in medical and electronic applications for their reliability and cost-effectiveness.
