Chemistry: Basic Concepts and Measurements

Flashcards covering introductory chemistry concepts including classification of matter, units of measurement, laws of chemical combination, and the mole concept.

Chemistry

The study of matter, its physical and chemical properties, and the physical and chemical changes it undergoes under different conditions.

Matter

Anything that occupies space and has mass.

Pure Substances

Substances that have a definite chemical composition and always have the same properties regardless of their origin.

Mixtures

Substances that have no definite chemical composition and hence no definite properties.

Elements

Pure substances which cannot be broken down into simpler substances by ordinary chemical changes; classified as metals, nonmetals, and metalloids.

Metals

Elements characterized by a shiny appearance (lustre), the ability to conduct heat and electricity, and being ductile and malleable.

Non-metals

Elements that usually have no lustre, are poor conductors of heat and electricity, and are brittle.

Metalloids

Elements with properties intermediate between metals and non-metals, such as arsenic, silicon, and germanium; also called semi-metals.

Compounds

Pure substances which can be broken down into simpler substances by ordinary chemical changes, composed of elements combined in a fixed proportion.

Homogeneous Mixtures

Mixtures where the molecules of the constituent solute and solvent are uniformly mixed throughout the bulk; also known as solutions.

Heterogeneous Mixtures

Mixtures where the molecules of the constituents are not uniformly mixed throughout the bulk, such as a suspension of an insoluble solid in a liquid.

Physical Properties

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

Chemical Properties

Properties exhibited when substances undergo a chemical change, resulting in a change in chemical composition.

Units

Arbitrarily decided and universally accepted standards used for quantitative measurements.

Sl Fundamental Units

The seven base units of the International System: metre ($m$), kilogram ($kg$), second ($s$), ampere ($A$), Kelvin ($K$), mole ($mol$), and candela ($cd$).

Mass

An inherent property of matter that measures the quantity of matter a body contains and does not vary with position.

Weight

The result of the mass and gravitational attraction on a body; it varies based on the distance from the centre of the earth.

Volume

The amount of space occupied by a three-dimensional object, with SI units expressed as cubic metres ($m^3$).

Density

The mass of a substance per unit volume, with the SI unit being $kg\,m^{-3}$.

Fahrenheit Scale Relationship

The mathematical relationship used to convert between Celsius and Fahrenheit: $\text{°F} = \frac{9}{5}(\text{°C}) + 32$.

Kelvin Scale Relationship

The mathematical relationship used to connect the Kelvin scale to the Celsius scale: $K = \text{°C} + 273.15$.

Law of Conservation of Mass

A law stated by Antoine Lavoisier which posits that 'mass can neither be created nor destroyed' in a chemical reaction.

Law of Definite Proportions

Also known as the Law of Definite Composition, it states that a given compound always contains exactly the same proportion of elements by weight.

Law of Multiple Proportions

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

Gay Lussac Law of Gaseous Volume

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

Avogadro Law

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

Dalton's Atomic Theory

A theory proposing that matter consists of tiny indivisible particles called atoms, and that chemical reactions involve only the reorganization of these atoms.

Atomic Mass Unit (amu)

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

Unified Mass Unit

A recently introduced unit replacing amu, called the dalton (symbol '$u$' or '$Da$').

Average Atomic Mass

The weighted average of the atomic masses of the naturally occurring isotopes of an element, based on their relative abundance.

Molecular Mass

The sum of average atomic masses of all the atoms of elements that constitute a molecule.

Formula Mass

The sum of atomic masses of the atoms present in the formula of ionic compounds, such as $NaCl$, that do not contain discrete molecules.

Mole

The amount of a substance that contains as many entities as there are atoms in exactly $12\,g$ of the carbon-12 isotope.

Avogadro's Constant ($N_A$)

The number of entities in one mole of a substance, equal to $6.0221367 \times 10^{23}\,\text{particles/mol}$.

Molar Mass

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