Definitions [13]
Define matter
Anything that has mass and occupies space is called matter.
Define interconversion of states of matter.
The process by which matter changes from one state to another and back to the original state, without any change in its chemical composition.
Define the term ‘amorphous’.
The solids which do not possess the repeating ordered arrangement of atoms or ions are called amorphous solids.
Define unit cell.
A basic repeating structural unit of a crystalline solid is called a unit cell.
Define Anisotropy.
The ability of crystalline solids to change values of physical properties when measured in different directions is called anisotropy.
Packing efficiency is the ratio of volumes occupied by atoms in unit cell to the total volume of the unit cell. It is also known as the packing fraction or the density of packing.
A doped semiconductor, having higher conductivity than a pure intrinsic semiconductor, is an extrinsic semiconductor.
A pure semiconductor with very low but finite electrical conductivity is called an intrinsic semiconductor.
The process by which impurities are introduced into semiconductors to enhance their conductivity is called doping.
A doped semiconductor, having higher conductivity than a pure intrinsic semiconductor, is an extrinsic semiconductor.
A pure semiconductor with very low but finite electrical conductivity is called an intrinsic semiconductor.
The process by which impurities are introduced into semiconductors to enhance their conductivity is called doping.
Define the following term:
Ferromagnetism
Ferromagnetism is defined as the phenomenon in which substances, such as iron, cobalt and nickel, are strongly attracted by a magnetic field. Such substances are called ferromagnetic substances.
Formulae [1]
Packing fraction or Packing efficiency = \[\frac{\text{Total volume of spheres}}{\text{Volume of the unit cell}}\times100\]
Theorems and Laws [2]
Name the law or principle to which the following observations confirm:
When 9650 coulombs of electricity is passed through a solution of copper sulphate, 3.175 g of copper is deposited on the cathode (at. wt. of Cu = 63.5).
Faraday’s first law of electrolysis: The mass of a substance deposited or liberated at an electrode is directly proportional to the quantity of electricity passed through the electrolyte.
Given: Charge passed = 9650 C
Atomic mass of Cu = 63.5
Valency of Cu in CuSO4 = 2
Equivalent mass of Cu = `63.5/2` = 31.75
Now, Mass deposited = `9650/96500 xx 31.75`
= 0.1 × 31.75
= 3.175 g
Name the law or principle to which the following observations confirm:
When 9650 coulombs of electricity is passed through a solution of copper sulphate, 3.175 g of copper is deposited on the cathode (at. wt. of Cu = 63.5).
Faraday’s first law of electrolysis: The mass of a substance deposited or liberated at an electrode is directly proportional to the quantity of electricity passed through the electrolyte.
Given: Charge passed = 9650 C
Atomic mass of Cu = 63.5
Valency of Cu in CuSO4 = 2
Equivalent mass of Cu = `63.5/2` = 31.75
Now, Mass deposited = `9650/96500 xx 31.75`
= 0.1 × 31.75
= 3.175 g
Key Points
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Mean molecular separation | ~3–5 Å | ~3–10 Å | >5 Å |
| Particle arrangement | Tightly packed, regular | Loosely packed, irregular | Highly irregular |
| Particle movement | Fixed positions, cannot move freely | Moves a small distance within liquid | Continuous random motion |
| Shape & volume | Definite shape and volume | Takes shape of container, definite volume | Takes shape and volume of container |
| Intermolecular space | Very small | Moderate | Large |
| Effect of temperature | Small volume change | Moderate volume change | Significant volume change |
| Compressibility | Practically incompressible | Slightly compressible | Highly compressible |
| Example | A piece of iron | Water, spirit, oil | Air |
| Property | Ionic Solids | Covalent Network Solids | Molecular Solids | Metallic Solids |
|---|---|---|---|---|
| Particles | Cations and anions | Covalently bonded atoms | Mono/polyatomic molecules | Metal ions in a sea of electrons |
| Forces | Electrostatic | Covalent bonds | London, dipole-dipole, H-bonding | Metallic bonds |
| Hardness | Hard and brittle | Very hard | Soft | Soft to very hard |
| Melting point | 600–3000°C | 1200–4000°C | Low (−272 to 400°C) | −39 to 3400°C |
| Conductivity | Poor (solid); good (molten/aqueous) | Poor (except graphite; diamond conducts heat) | Poor | Good conductor of heat and electricity |
| Examples | NaCl, CaF₂ | Diamond, silica | Ice, benzoic acid | Na, Mg, Cu, Au |
Solids are classified into three groups based on conductivity:
| Type | Conductivity (Ohm⁻¹ m⁻¹) | Band Gap | Reason | Examples |
|---|---|---|---|---|
| Metallic conductors | 10⁴ – 10⁷ (very high) | No band gap (overlapping s & p bands) | Motion of electrons | Cu, Al, Ag |
| Insulators | 10⁻²⁰ – 10⁻¹⁰ (very low) | Large (forbidden zone) | Electrons cannot cross | Diamond, wood, rubber |
| Semiconductors | 10⁻⁶ – 10⁴ (moderate) | Small | Motion of interstitial electrons/holes | Si, Ge |
Conductivity of metals decreases with increase in temperature; conductivity of semiconductors increases with temperature.
Solids are classified into three groups based on conductivity:
| Type | Conductivity (Ohm⁻¹ m⁻¹) | Band Gap | Reason | Examples |
|---|---|---|---|---|
| Metallic conductors | 10⁴ – 10⁷ (very high) | No band gap (overlapping s & p bands) | Motion of electrons | Cu, Al, Ag |
| Insulators | 10⁻²⁰ – 10⁻¹⁰ (very low) | Large (forbidden zone) | Electrons cannot cross | Diamond, wood, rubber |
| Semiconductors | 10⁻⁶ – 10⁴ (moderate) | Small | Motion of interstitial electrons/holes | Si, Ge |
Conductivity of metals decreases with increase in temperature; conductivity of semiconductors increases with temperature.
Motion of electrons generates a magnetic field — each electron behaves like a tiny bar magnet with a magnetic moment measured in Bohr Magneton (μ_B) = 9.27 × 10⁻²⁴ A m².
| Type | Nature | Electron Configuration | Examples |
|---|---|---|---|
| Diamagnetic | Weakly repelled by magnetic field; magnetised in opposite direction | All electrons paired | NaCl, H₂O, N₂, C₆H₆, F₂, benzene |
| Paramagnetic | Weakly attracted by magnetic field; magnetised in same direction | Unpaired electrons; lose magnetism when field removed | O₂, Cu²⁺, Fe³⁺, Cr³⁺ |
| Ferromagnetic | Strongly attracted; can be permanently magnetised (all domains align in field direction) | Unpaired electrons + aligned domains | Fe, Co, Ni, Gd, CrO₂ |
Concepts [28]
- States of Matter
- General Characteristics of Solid State
- Amorphous and Crystalline Solids
- Classification of Crystalline Solids
- Bragg's Law and Its Applications
- Crystal Lattices and Unit Cells
- Crystal Lattices and Unit Cells - Primitive and Centred Unit Cells
- Number of Atoms in a Unit Cell
- Close Packed Structures of Solids
- Close Packed Structures - Formula of a Compound and Number of Voids Filled
- Packing Efficiency
- Packing Efficiency in Simple Cubic Lattice
- Efficiency of Packing in Body-centred Cubic Structures
- Packing Efficiency in hcp and ccp Structures
- Calculations Involving Unit Cell Dimensions
- Imperfections in Solids - Introduction
- Imperfections in Solids
- Types of Point Defects - Stoichiometric Defects
- Types of Point Defects - Non-stoichiometric Defects
- Types of Point Defects - Impurity Defects
- Properties of Solids: Electrical Properties
- Properties of Solids: Electrical Properties
- Conduction of Electricity in Metals
- Conduction of Electricity in Semiconductors
- Applications of n-type and p-type Semiconductors
- Properties of Solids: Magnetic Properties
- Solid State
- Band Theory of Metals
