basic concepts of Chemistry

Law of Conservation of Mass

Principle stating that mass is neither created nor destroyed during a chemical reaction, meaning the total mass of reactants equals the total mass of products.

Law of Definite Proportions

Principle stating that a chemical compound always contains its constituent elements in fixed proportions by mass, regardless of source or method of preparation.

Law of Multiple Proportions

Principle 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 ratios of small whole numbers.

Law of Reciprocal Proportions

Principle stating that when two elements combine separately with a third element, their mass ratios are either the same or simple multiples of each other.

Gay-Lussac's Law of Combining Volumes

Principle stating that reacting gases combine in volumes that bear simple whole-number ratios to one another and to gaseous products at constant temperature and pressure.

Avogadro's Law

Principle stating that equal volumes of gases at the same temperature and pressure contain the same number of molecules.

Antoine Lavoisier

French chemist who proposed the Law of Conservation of Mass in 1789.

Joseph Proust

French chemist who formulated the Law of Definite Proportions.

John Dalton

English chemist who proposed the Law of Multiple Proportions and published 'A New System of Chemical Philosophy' in 1808.

Jeremias Benjamin Richter

German chemist who proposed the Law of Reciprocal Proportions in 1792.

Base SI unit for mass

Kilogram ($kg$)

Base SI unit for temperature

Kelvin ($K$)

Base SI unit for amount of substance

Mole ($mol$)

Base SI unit for luminous intensity

Candela ($cd$)

Base SI unit for electric current

Ampere ($A$)

Formula relating Fahrenheit and Celsius temperature scales

$$^\frac{\text{o}}{\text{c}}\text{F} = \frac{9}{5}(^\frac{\text{o}}{\text{c}}\text{C}) + 32$$

Formula relating Kelvin and Celsius temperature scales

$$K = ^\frac{\text{o}}{\text{c}}\text{C} + 273.15$$

Mass

The amount of matter present in an object, which remains constant regardless of location.

Weight

The gravitational force exerted on an object, which varies with local gravitational field strength.

Density

Mass per unit volume of a substance, represented by $\rho$ with SI unit $kg\,m^{-3}$.

Atomic Mass Unit ($amu$ or $u$)

Unit defined as exactly $\frac{1}{12}$th of the mass of one carbon-12 ($^{12}\text{C}$) atom.

Avogadro's Number

The total number of particles present in one mole of any substance, equal to $6.022 \times 10^{23}$.

Dalton's Atomic Theory

Model proposing that matter consists of indivisible atoms, atoms of a given element are identical, compounds form in fixed ratios, and chemical reactions rearrange atoms without creating or destroying them.