Basic Concepts of Chemistry

Introduction

• Importance of understanding basic concepts in chemistry.
• Chemistry: science of atoms, molecules, and their transformations.
• Understanding properties, composition, and interactions of matter.
• Focus on fundamental principles; essential for further studies in chemistry.

What is Chemistry?

• Chemistry: science of atoms, molecules, and their transformations.
• Perspective: view everything as matter consisting of atoms and molecules.
• Focus on transformations, e.g., formation of diamonds from coal.

States of Matter

• Solid: Particles closely packed, fixed shape, and volume.
• Liquid: Particles relatively close, fixed volume but no fixed shape.
• Gas: Particles far apart, neither fixed shape nor volume.
• Interconvertibility of states: solid→liquid (melting), liquid→gas (vaporization), gas→solid (deposition).

Classification of Matter

• Pure Substances: Fixed composition, e.g., elements and compounds.
• Mixtures: Varying composition, e.g., homogeneous and heterogeneous.

Pure Substances

• Elements: Single type of atom, e.g., gold, silver.
• Compounds: Combinations of different atoms, fixed ratios, e.g., water (H₂O).

Mixtures

• Homogeneous: Uniform composition, e.g., salt dissolved in water.
• Heterogeneous: Non-uniform composition, e.g., sand in water.

Properties of Matter

• Physical Properties: Observable and measurable without changing the substance, e.g., color, melting point.
• Chemical Properties: Requires a chemical change to observe, e.g., acidity, reactivity.

SI Units and Measurements

• Importance of standard units (SI units) for consistency.
• Examples: meter (length), kilogram (mass), second (time), Kelvin (temperature).
• Use of scientific notation for large and small numbers.

Atomic and Molecular Mass

• Atomic Mass: Mass of a single atom, usually expressed in atomic mass units (amu).
• Molecular Mass: Sum of atomic masses of atoms in a molecule.

The Mole Concept

• Mole: Unit for quantity, 1 mole = 6.022 × 10²³ entities (Avogadro's number).
• Importance in converting between atoms/molecules and grams.

Percentage Composition

• Calculation method for determining the percentage of each element in a compound.

Empirical and Molecular Formulas

• Empirical Formula: Simplest whole-number ratio of elements in a compound.
• Molecular Formula: Actual number of atoms of each element in a molecule.

Chemical Reactions

• Balanced Chemical Equations: Ensure mass conservation by balancing the number of atoms of each element on both sides.

Limiting Reagents

• Definition: reagent that determines the amount of product formed in a reaction.
• Important for determining theoretical yields.

Solutions and Their Concentrations

• Solution: Homogeneous mixture, consists of solute and solvent.
• Concentration units: mass percent, mole fraction, molarity, molality.