Unit 1 – Some Basic Concepts of Chemistry (Vocabulary)

Vocabulary flashcards summarising key terms and definitions from ‘Unit 1 – Some Basic Concepts of Chemistry,’ covering historical background, measurement, laws of combination, atomic theory, and solution chemistry.

Chemistry

The branch of science that studies the preparation, properties, structure and reactions of material substances.

Alchemy

Early form of chemistry focused on transmuting base metals into gold and discovering the ‘elixir of life.’

Iatrochemistry

Medieval Indian chemical tradition concerned with medicines and health-related preparations.

Rasayan Shastra

Ancient Indian term for chemistry encompassing metallurgy, medicine, cosmetics, glass, dyes, etc.

Philosopher’s Stone

Legendary alchemical substance believed to convert base metals into gold.

Elixir of Life

Mythical substance sought by alchemists to grant immortality.

Matter

Anything that has mass and occupies space.

Solid

State of matter with definite shape and volume; particles are closely packed in an orderly fashion.

Liquid

State of matter with definite volume but no definite shape; particles are close but can move around.

Gas

State of matter with neither definite volume nor shape; particles are far apart and move freely.

Mixture

A physical combination of two or more substances in variable ratios; components can be separated physically.

Pure Substance

Material with uniform composition; all constituent particles are identical in chemical nature.

Element

Pure substance whose particles contain only one kind of atom.

Compound

Pure substance formed when atoms of two or more elements combine in a fixed ratio.

Homogeneous Mixture

Mixture whose composition is uniform throughout; components are indistinguishable.

Heterogeneous Mixture

Mixture with non-uniform composition; different components are visible or detectable.

Physical Property

Characteristic observed without changing a substance’s composition (e.g., colour, density, boiling point).

Chemical Property

Characteristic that becomes evident during a chemical change (e.g., combustibility, acidity).

SI Unit

Internationally agreed base or derived unit used for scientific measurement.

Metre (m)

SI base unit of length; distance light travels in vacuum in 1/299 792 458 s.

Kilogram (kg)

SI base unit of mass defined via the Planck constant.

Second (s)

SI base unit of time based on 9 192 631 770 periods of radiation of Cs-133.

Kelvin (K)

SI base unit of thermodynamic temperature; linked to the Boltzmann constant.

Mole (mol)

SI base unit for amount of substance containing exactly 6.022 140 76 × 10²³ entities.

Avogadro Constant (N_A)

The fixed number 6.022 140 76 × 10²³ entities per mole.

Density

Mass per unit volume of a substance; SI unit kg m⁻³.

Atomic Mass Unit (u)

1⁄12 of the mass of a carbon-12 atom; used to express atomic and molecular masses.

Average Atomic Mass

Weighted average of isotopic masses of an element based on natural abundance.

Molecular Mass

Sum of atomic masses of atoms in a molecule.

Formula Mass

Sum of atomic masses in a formula unit of an ionic compound like NaCl.

Mass Percent

(Mass of element ÷ Molar mass of compound) × 100; expresses elemental composition.

Empirical Formula

Simplest whole-number ratio of elements in a compound.

Molecular Formula

Actual number of each type of atom in one molecule of a compound.

Stoichiometry

Quantitative study of reactants and products in a chemical reaction using a balanced equation.

Limiting Reagent

Reactant that is completely consumed first, limiting the amount of product formed.

Mole Fraction

Ratio of moles of a component to total moles in a mixture or solution.

Molarity (M)

Moles of solute per litre of solution.

Molality (m)

Moles of solute per kilogram of solvent.

Significant Figures

Digits in a measurement that are known with certainty plus one doubtful digit, reflecting precision.

Scientific Notation

Way of expressing numbers as N × 10ⁿ where 1 ≤ N < 10 and n is an integer.

Law of Conservation of Mass

Matter is neither created nor destroyed in a chemical reaction; total mass remains constant.

Law of Definite Proportions

A compound always contains the same elements in the same mass ratio.

Law of Multiple Proportions

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in simple whole-number ratios.

Gay-Lussac’s Law of Gaseous Volumes

Gases react in simple whole-number ratios by volume at constant temperature and pressure.

Avogadro’s Law

Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.

Dalton’s Atomic Theory

Early theory stating that matter is made of indivisible atoms which combine in simple ratios to form compounds.

Dimensional Analysis

Method of converting units using factor-label (unit-factor) technique.

Analytical Balance

High-precision instrument for measuring mass, capable of determining masses to 0.1 mg or better.