Chem Module 11 Study Guide

Kinetic Molecular Theory (KMT)

A comprehensive model that describes the behavior of gases based on the idea that these substances are composed of numerous small particles that are in constant, rapid motion.

Assumption 1

Particle Size: In gases, the sizes of individual particles are negligible compared to the vast amounts of empty space between them, which is a fundamental concept in gas behavior.

Assumption 2

Particle Motion: Gas particles are perpetually in random motion, colliding with each other and with the walls of their container; these collisions are perfectly elastic, meaning there is no loss of kinetic energy.

Assumption 3

Particle Energy: Each gas particle possesses kinetic energy, which can be calculated by the formula KE = 1/2 mv², where m is the mass and v is the velocity of the particle.

Low Density

Gases display significantly lower density compared to solids and liquids due to the large volume occupied by gas particles in relation to their mass.

Diffusion

The process whereby gas particles intermingle and spread from regions of higher concentration to lower concentration, driven by their random motion.

Effusion

The process in which gas particles escape through a small hole into a vacuum or another space, where the speed of effusion is affected by the mass of the particles.

Pressure

Defined as the force exerted by gas particles colliding with the surfaces of their container per unit area; mathematically, Pressure = Force/Area.

Barometer

An instrument specifically designed to measure atmospheric pressure using a column of mercury or other fluid; variations in pressure can indicate weather changes.

Pascal (Pa)

The SI (International System of Units) unit of pressure, which is defined as one newton of force applied over an area of one square meter.

Dalton's Law of Partial Pressures

This law states that in a mixture of gases, the total pressure exerted is equal to the sum of the partial pressures of each individual gas in the mixture.

Intermolecular Forces

The attractive forces that exist between individual molecules or atoms, which significantly influence the physical properties of substances.

Dispersion Forces

Weak and temporary forces that arise from the momentary distributions of electron density in nonpolar molecules, leading to an induced dipole.

Dipole-Dipole Forces

Attractive forces that occur between the positively charged end of one polar molecule and the negatively charged end of another, influencing boiling points and solubility.

Hydrogen Bonds

A particularly strong type of dipole-dipole interaction that occurs when hydrogen is covalently bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine.

Viscosity

A measure of a fluid's resistance to flow, determined by the strength of intermolecular forces and temperature; higher viscosity corresponds to slower flow.

Surface Tension

The cohesive force at the surface of a liquid that occurs due to the attractive forces between liquid molecules, resulting in a 'skin' effect.

Cohesion

The intermolecular attraction between identical molecules, which contributes to liquid droplet formation and surface tension.

Adhesion

The attraction between different types of molecules, such as water molecules and the molecules of a solid surface, facilitating processes like capillary action.

Crystalline Solids

Solids characterized by a highly ordered and repeating geometric arrangement of their constituent particles, leading to distinct structural properties.

Amorphous Solids

Solids that lack a definite geometric structure; their particles are arranged randomly, resulting in varying properties compared to crystalline solids.

Phase Changes

Processes by which matter transitions between solid, liquid, and gas states, accompanied by the absorption or release of energy.

Vaporization

The process in which a liquid is converted into its gaseous state, occurring either through boiling or evaporation.

Sublimation

The direct transition of a solid into gas without passing through the liquid state, such as in the case of dry ice.

Condensation

The process where gaseous particles lose energy and transition into the liquid phase, commonly observed as dew on cool surfaces.

Freezing

The transition process where a liquid loses thermal energy and forms a structured solid, typically resulting in an organized crystal lattice.

Triple Point

The specific condition of temperature and pressure at which all three phases of a substance (solid, liquid, gas) coexist in thermodynamic equilibrium.

Critical Point

A particular temperature and pressure where a substance's distinct liquid and gas phases cease to exist, resulting in a supercritical fluid.