Fundamental Principles of Chemistry and Atomic Theory

Fundamental Laws of Chemistry

Magnitude: It is any quality that characterizes bodies or phenomena that can be measured and expressed through numbers.

Law of Conservation of Mass: In any chemical reaction that takes place in an enclosed space, the total mass of substances present there is conserved. The mass of the reactants is the same as the mass of the products.

Proust's Law: When combining two or more chemical elements to give a particular compound, they always do so in a fixed proportion, whatever its physical state.

Dalton's Law: If two elements can be combined to form more than one compound, a fixed amount of one of them is combined with variable amounts of the other elements, so that the related quantities are simple numbers.

Dalton's Atomic Theory

• 1. The chemical elements are formed by small particles called atoms that are indivisible and inseparable.
• 2. All atoms of the same element are equal and therefore have the same mass and properties, whereas atoms of different elements have different mass and properties.
• 3. Chemical compounds are formed by the union of different element atoms, and these atoms combine with each other in a ratio of simple numbers.
• 4. Atoms are not created or destroyed in a chemical reaction; they are only redistributed.

Kinetic Molecular Theory

• 1. Gases are formed by particles. The size of these is negligible compared with the distance between them.
• 2. Gas molecules move continuously and randomly, colliding with each other and with the walls of the container.
• 3. The collisions that arise are completely elastic; that is, there is no variation in kinetic energy.
• 4. The average kinetic energy of gas molecules is directly proportional to the temperature of the sample.

Solutions and Atomic Variations

Solubility: The solubility of a substance in a given solvent at a specific temperature is the concentration of solute in its saturated solution.

Osmosis: When solutions of two different concentrations are separated by a semipermeable membrane, the solvent passes from the less concentrated solution to the more concentrated one.

Reverse Osmosis: This technique uses high pressures to force water from a more concentrated solution to a less concentrated one.

Isotopes: There are different kinds of atoms that form an element. Isotopes have the same atomic number, but the mass number is different because they differentiate in the number of neutrons.