Some Baise Concept of Chemistry

Practice flashcards covering the fundamental definitions, laws, and measurements in chemistry as presented in the lecture notes.

Chemistry

A branch of science which deals with the study of composition, structure and properties of matter.

Matter

Anything which has mass and occupies space.

Solids

A state of matter where particles are held very close to each other in an orderly arrangement with limited freedom of movement, resulting in a definite volume and definite shape.

Liquids

A state of matter where particles are close to each other but can move around, possessing a definite volume but no definite shape.

Gases

A state of matter where particles are far apart and move easily and fastly, having neither a definite volume nor a fixed shape.

Mixture

Matter which contains two or more substances.

Homogeneous Mixture

A mixture in which the composition is uniform throughout, such as a sugar solution in water.

Heterogeneous Mixture

A mixture in which the composition is not uniform throughout and different components are sometimes visible, such as a mixture of salt and sugar.

Pure substance

A substance made up of only one kind of particles with a fixed composition.

Elements

A pure substance containing only one type of particles, which may exist as atoms or molecules.

Compounds

A combination of two or more atoms of different elements in a definite ratio; its constituents cannot be separated by physical methods.

Physical Properties

Properties that can be measured or observed without changing the identity or composition of the substance, including colour, odour, melting points, boiling points, and density.

Chemical Properties

Properties requiring a chemical change to occur for their measurement or observation, such as combustibility and reactivity with acids and bases.

Weight

Defined by the formula $Weight = Mass \times Gravitational Force$. It may vary from one place to another due to changes in gravity.

Density

The ratio of mass to volume ($Density = \frac{Mass}{Volume}$) with the SI unit of $kgm^{-3}$.

Significant Figures

Meaningful digits which are known with certainty plus one which is estimated or uncertain.

Precision

Refers to 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

Mass can neither be created nor be destroyed.

Law of Definite Proportions

A compound always contains exactly the same proportion of elements by weight.

Law of Multiple Proportion

If two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in the ratio of small whole numbers.

Gay Lussac's Law of Gaseous Volume

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

Avogadro's Law

Equal volumes of all gases at the same temperature and pressure should contain an equal number of molecules.

One Atomic Mass Unit (amu)

Exactly equal to one twelfth of the mass of one Carbon-12 atom, where $1 \text{ amu} = 1.66056 \times 10^{-24} \text{ g}$.

Average Atomic Mass

The average mass of an element calculated by taking into account the masses of its isotopes and their natural abundances: \frac{\text{sum of (mass of isotopes} \times \text{% Natural Abundance)}}{100}.

Gram Atomic Mass

The mass of one mole of an element's atoms, expressed in grams.

Molecular Mass

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

Formula Mass

The sum of the atomic masses of the constituent atoms in an ionic compound.

One Mole

The amount of a substance that contains as many particles or entities as there are atoms in exactly $12 \text{ g}$ ($0.012 \text{ kg}$) of the $^{12}C$ isotope.

Molar Mass

The mass of one mole of a substance in grams.

Percentage Composition

The ratio of each element in a compound to the total mass of the compound, expressed as a percentage.

Empirical Formula

A formula that gives the simplest whole number ratio of various atoms in a compound.

Molecular Formula

A formula that determines the exact number of different types of atoms present in a molecule of a compound.

Stoichiometry

The calculation of masses (and sometimes volumes) of the reactants and products involved in a chemical reaction based on a balanced equation.

Limiting Reagent

The reactant that is consumed first and limits the amount of product formed in a chemical reaction.

Mass Per cent

The ratio of the mass of solute to the mass of the solution, expressed as a percentage: $\text{Mass Percent} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$.

Mole Fraction

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

Molarity

The number of moles of solute in $1 \text{ l}$ of solution.

Molality

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