Unit 1: Some Basic Concepts of Chemistry

Comprehensive vocabulary flashcards covering the basic concepts of chemistry including historical context, states of matter, units of measurement, laws of chemical combination, and stoichiometric calculations.

Chemistry

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

Philosopher’s stone (Paras)

A substance sought by early chemists believed to be capable of converting baser metals like iron and copper into gold.

Elixir of life

A substance sought in the development of chemistry believed to grant immortality.

Rasayan Shastra

The name for chemistry in ancient India, which included metallurgy, medicine, and the manufacture of cosmetics, glass, and dyes.

Acharya Kanda

Born in 600 BCE and also known as Kashyap, he was the first proponent of the ‘atomic theory’ and authored the text Vaiseshika Sutras.

Paramãnu

The name given by Acharya Kanda to small indivisible particles, comparable to atoms, which are eternal, indestructible, and spherical.

Bhasma

Metal-based preparations mentioned in the Charaka Samhita for treating ailments; modern science has proved they contain nanoparticles of metals.

Matter

Anything which has mass and occupies space.

Solid

A state of matter where particles are held very close together in an orderly fashion with restricted movement, resulting in a definite volume and definite shape.

Liquid

A state of matter with a definite volume but no definite shape, where particles are close but able to move around.

Gas

A state of matter with neither definite volume nor definite shape, characterized by particles that are far apart and move easily and fast.

Pure Substance

A substance where all constituent particles are same in chemical nature and have a fixed composition.

Homogeneous Mixture

A mixture where the components are uniformly distributed throughout and the composition is uniform throughout, such as air or a sugar solution.

Heterogeneous Mixture

A mixture where the composition is not uniform throughout and different components are sometimes visible, such as salt and sugar mixed together.

Element

A substance consisting of only one type of atoms, existing either as individual atoms or as molecules.

Compound

A substance obtained when two or more atoms of different elements combine together in a definite ratio; its properties differ from those of its constituent elements.

Physical Properties

Properties such as colour, odour, melting point, and density that can be measured or observed without changing the identity of the substance.

Chemical Properties

Properties that require a chemical change to be observed, such as composition, combustibility, and reactivity with acids and bases.

SI System

The International System of Units (Le Systeme International d’Unités), established by the 11th General Conference on Weights and Measures (CGPM).

Mass

The amount of matter present in a substance, which remains constant regardless of location.

Weight

The force exerted by gravity on an object, which may vary from one place to another.

Density

The amount of mass per unit volume, calculated as $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$, with SI units of $\text{kg}\text{m}^{-3}$.

Scientific Notation

An exponential notation in the form $N \times 10^n$, where $n$ is an exponent and $N$ is a digit term between 1.000… and 9.999….

Significant Figures

Meaningful digits in a measurement which are known with certainty plus one digit that is estimated or uncertain.

Precision

The closeness of various measurements for the same quantity.

Accuracy

The agreement of a particular value to the true value of the result.

Law of Conservation of Mass

A law put forth by Antoine Lavoisier in 1789 stating that matter can neither be created nor destroyed during physical or chemical changes.

Law of Definite Proportions

A law stated by Joseph Proust which says a given compound always contains exactly the same proportion of elements by weight.

Law of Multiple Proportions

A law proposed by Dalton in 1803 stating that if two elements form more than one compound, the masses of one element combining with a fixed mass of the other are in the ratio of small whole numbers.

Gay Lussac’s Law of Gaseous Volumes

States that when gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume at the same temperature and pressure.

Avogadro’s Law

Proposed in 1811, it states that equal volumes of all gases at the same temperature and pressure should contain equal number of molecules.

Atomic Mass Unit (amu)

A mass exactly equal to one-twelfth of the mass of one carbon-12 atom; $1\,\text{amu} = 1.66056 \times 10^{-24}\,\text{g}$.

Molecular Mass

The sum of atomic masses of the elements present in a molecule.

Formula Mass

The sum of atomic masses used for compounds like sodium chloride (NaCl) that consist of ions arranged in a three-dimensional structure rather than discrete molecules.

Mole (mol)

The SI unit for the amount of substance, containing exactly $6.02214076 \times 10^{23}$ elementary entities.

Molar Mass

The mass of one mole of a substance in grams, which is numerically equal to its atomic, molecular, or formula mass in $u$.

Empirical Formula

The formula representing the simplest whole number ratio of various atoms present in a compound.

Molecular Formula

The formula showing the exact number of different types of atoms present in a molecule of a compound.

Stoichiometry

The calculation of masses and sometimes volumes of reactants and products involved in a chemical reaction.

Limiting Reagent

The reactant that is present in the least amount and is consumed first, thereby limiting the amount of product formed.

Mass Per Cent

The concentration of a solute expressed as $\frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$.

Mole Fraction

The ratio of the number of moles of a particular component to the total number of moles of the solution.

Molarity (M)

The number of moles of the solute present in 1 litre of the solution; it is temperature dependent.

Molality (m)

The number of moles of solute present in $1\,\text{kg}$ of solvent; it does not change with temperature.