CHEMISTRY

by vardhan Chemistry

PERIODIC TABLE

Definition: The periodic table is a tabular arrangement of elements, organized by increasing atomic number, electron configuration, and recurring chemical properties.

Structure:

  • Periods: Horizontal rows (7 in total) that represent the number of electron shells.
  • Groups: Vertical columns (18 in total) that contain elements with similar chemical properties and the same number of valence electrons.
  • Explanation:
  • Elements are arranged in order of increasing atomic number.
  • Elements in the same group have similar chemical and physical properties.
  • The periodic table helps predict the properties and behaviors of elements.

CHEMICAL REACTIONS:-

Definition: A chemical reaction is a process in which substances (reactants) undergo chemical changes to form new substances (products).

Types of Reactions:

  1. Synthesis Reaction: Two or more simple substances combine to form a more complex substance (A + B → AB).
  2. Decomposition Reaction: A complex substance breaks down into two or more simpler substances (AB → A + B).
  3. Single Replacement Reaction: One element replaces another in a compound (A + BC → AC + B).
  4. Double Replacement Reaction: Two compounds exchange elements or groups of elements to form two new compounds (AB + CD → AD + CB).
  5. Combustion Reaction: A substance combines with oxygen, releasing energy in the form of light or heat (CxHy + O₂ → CO₂ + H₂O).

ATOMIC STRUCTURE

Definition: The atomic structure refers to the arrangement of subatomic particles—protons, neutrons, and electrons—in an atom.

Components:

  1. Protons: Positively charged particles found in the nucleus.
  2. Neutrons: Neutral particles found in the nucleus.
  3. Electrons: Negatively charged particles orbiting the nucleus in electron shells.

Explanation:

  • The number of protons (atomic number) determines the element.
  • Neutrons contribute to the mass of the atom and can vary in number, leading to different isotopes of the same element.
  • Electrons are arranged in shells around the nucleus, and their arrangement determines the atom’s chemical properties.

STATES OF MATTER:-

Definition: States of matter refer to the distinct forms that different phases of matter take on. The primary states are solid, liquid, gas, and plasma.

Characteristics:

  • Solid: Defined shape and volume, particles tightly packed.
  • Liquid: Defined volume but no defined shape, particles less tightly packed than in solids.
  • Gas: Neither defined shape nor volume, particles are far apart and move freely.
  • Plasma: Ionized gas with free electrons, found in stars and fluroscent lights.

ACIDS AND BASES:-

Definition: Acids and bases are two classes of compounds that have specific properties and react with each other to form water and salts.

Characteristics:

  • Acids: Substances that donate protons (H⁺ ions) in solution. Have a sour taste, turn blue litmus paper red, and have pH less than 7.
  • Bases: Substances that accept protons or donate hydroxide ions (OH⁻) in solution. Have a bitter taste, turn red litmus paper blue, and have pH greater than 7.

REACTION RATES:-

Definition: Reaction rates refer to the speed at which a chemical reaction occurs. It is a measure of how fast reactants are converted into products.

Factors Affecting Reaction Rates:

  1. Concentration: Higher concentration of reactants increases the reaction rate.
  2. Temperature: Increasing the temperature usually increases the reaction rate.
  3. Surface Area: Larger surface area of reactants leads to a faster reaction rate.
  4. Catalysts: Substances that increase the reaction rate without being consumed.
  5. Nature of Reactants: Different substances react at different speeds.

CHEMICAL EQUILIBRIUM:-

Definition: Chemical equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in the concentrations of reactants and products.

Characteristics:

  • Dynamic Equilibrium: Reactions continue to occur, but the concentrations remain constant.
  • Equilibrium Constant (K): A ratio of the concentration of products to reactants at equilibrium.

Le Chatelier’s Principle: If a system at equilibrium is disturbed, it will shift to counteract the disturbance and restore equilibrium.

  • Changes in Concentration: Adding or removing reactants/products will shift the equilibrium.
  • Changes in Temperature: Increasing temperature favors the endothermic direction.
  • Changes in Pressure: Affect gaseous reactions; increasing pressure favors the side with fewer gas molecules.

REDOX REACTIONS:-

Definition: Redox (reduction-oxidation) reactions involve the transfer of electrons between two species. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.

Oxidation and Reduction:

  • Oxidation: Loss of electrons (increase in oxidation state).
  • Reduction: Gain of electrons (decrease in oxidation state).

Oxidizing and Reducing Agents:

  • Oxidizing Agent: The substance that gets reduced.
  • Reducing Agent: The substance that gets oxidized

ORGANIC CHEMISTRY:-

Definition: Organic chemistry is the study of carbon-containing compounds and their properties, structures, and reactions.

Key Concepts:

  • Hydrocarbons: Compounds composed of only carbon and hydrogen. Includes alkanes (single bonds), alkenes (double bonds), and alkynes (triple bonds).
  • Functional Groups: Specific groups of atoms within molecules that determine the chemical properties of those molecules. Examples include hydroxyl groups (-OH), carboxyl groups (-COOH), and amino groups (-NH₂).

POLYMERS:-

Definition: Polymers are large molecules made up of repeating structural units called monomers, which are covalently bonded together.

Types of Polymers:

  • Natural Polymers: Occur naturally. Examples include proteins, DNA, and cellulose.
  • Synthetic Polymers: Man-made polymers. Examples include plastics like polyethylene and polystyrene.

ELECTROCHEMISTRY:-

Definition: Electrochemistry is the study of chemical processes that cause electrons to move, creating an electric current. It involves redox reactions and the study of how chemical energy is converted into electrical energy and vice versa.

Key Concepts:

  • Galvanic (Voltaic) Cells: Convert chemical energy into electrical energy. Example: batteries.
  • Electrolytic Cells: Use electrical energy to drive a non-spontaneous chemical reaction. Example: electroplating.

ANALYTICAL CHEMISTRY:-

Definition: Analytical chemistry involves the qualitative and quantitative analysis of chemical compounds to determine their composition and concentration.

Techniques:

  • Spectroscopy: Measures the interaction of light with matter (e.g., UV-Vis spectroscopy).
  • Chromatography: Separates mixtures based on their movement through a stationary phase (e.g., gas chromatography).
  • Titration: Determines the concentration of a solution by reacting it with a standard solution.

ENVIRONMENTAL CHEMISTRY:-

Definition: Environmental chemistry is the study of chemical processes occurring in the environment and their effects on human health and ecosystems.

Key Concepts:

  • Pollution: Contamination of the environment with harmful substances. Examples include air pollution, water pollution, and soil pollution.
  • Green Chemistry: Designing products and processes that minimize the use and generation of hazardous substances.
  • Climate Change: Chemical processes that contribute to global warming, such as the emission of greenhouse gases (e.g., CO₂, CH₄).