GENERAL CHEMISTRY

Kinetic Molecular Model/Theory- theory/experiment-based; explains the state of matter based on the idea that matter is composed of tiny particles that are always in motion or constant movement; describes behavior, interaction, movements of molecules

Kinetic Energy- energy of motion; energy in motion. Actively using energy for movement; provided by any substance;  moving particles

Molecule- a group of two or more atoms held together by attractive forces known as chemical bonds

States of Matter

1. Solid- rigid, not flexible; fixed in shape and volume; exists in different shapes; follow a pattern; closely packed; has properties of:

1. Malleability- material’s ability to be formed or hammered into thin sheets without breaking

2. Ductility- material’s ability to be stretched, pulled, or drawn into a thin wire or thread without breaking

2. Liquid- not rigid, not fixed in shape but fixed in volume; occupy the shape of its repository

3. Gas- not rigid, not fixed; moves freely and diffuses easily; low density; forces are weak and molecules move randomly

8 Phase Changes (M.I.C.E.S. Run From Dogs)

1. Melting- solid to liquid

2. Ionization- gas to plasma

3. Condensation- gas to liquid

4. Evaporation- liquid to gas

5. Sublimation- solid to gas

6. Recombination- plasma to gas

7. Freezing- liquid to solid

8. Deposition- gas to solid

Temperature Scales- Kelvin, Celsius, Rankine, Fahrenheit

Gas and Absolute Temperature

• If the absolute temperature scale increases, so does the kinetic energy

• Zero temperature is equal to absolute zero; coldest possible temperature where there is no internal energy; particles are stationary when temperature is at absolute zero (no motion/heat) 0 Kelvin = -273.15 ℃ or -460 ℉

Kinetic Energy- one of the forms of energy that an object/particle has the reason of its motion

Heat Flow- depends on attractive forces present in the substance

Volatility- ease of evaporation of a liquid or substance

Intermolecular Forces of Attraction

• the greater the amount of intermolecular forces, the greater the amount of energy required to overcome those forces; weaker than intramolecular forces; pertain to forces that hold molecules in a substance  and exist between molecules

• determine the state of matter and their physical properties such as:

1. Solid- heat fusion, melting point

2. Liquid- boiling point, viscosity, vapor pressure, heat of vaporization

3. Gas- expansibility, diffusibility, compressibility 

Types of Intermolecular Forces

1. Van der Waals Forces- named after Johaness Diderik van der Waals, a Dutch physicist; weakest of all intermolecular attractions between molecules 

1. London Dispersion Force- happens when one molecule with a temporary dipole exerts a weak attractive force on another molecule; responsible for condensation and solidification of these molecules

2. Dipole-dipole Interaction- occurs between partially positive (+) and partially negative (+) ends; interaction is observed in polar covalent molecules such as amino acids, wherein the electrons are shared by an oxygen atom; effective over short distance only as it is still weak; increase in temperature diminishes the strength of this interaction

• Hydrogen Bonding: a special kind of dipole-dipole interaction formed when hydrogen bonds with fluorine, oxygen or nitrogen; the distance needed is 2x-10 meters ; partially positive end of the hydrogen atom is attracted to the partially negative end of fluorine, oxygen, or nitrogen; weaker than ionic or covalent bonding but is the strongest intermolecular force of attraction; reason for the high melting and boiling point of water, ammonia, and alcohol such as methanol

2. Ion-dipole Interaction- arises from the interaction between an ion and a polar molecule; 15 kj/mol for 500 parts/mil distance; responsible for formation of cations in a solution

• If molecule is an anion (-), it will be attracted to the partially positive end of the polar molecule

• If molecule is a cation (+), it will be attracted to the partially negative end of the polar molecule

Intramolecular Forces of Attraction

• responsible for interaction with only the compound; generally stronger; within a single molecule; forces that hold atoms within a molecule

Types of Intramolecular Forces

1. Ionic Bonding

• atoms transfer electrons to each other; require at least one electron donor and one electron acceptor; folded structure; intramolecular forces exist within formula unit of ionic compound e.g. Table salt (NaCl)

2. Covalent Bonding

• the sharing of electrons between atoms; occurs between two atoms of the same element or of elements close to each other in the periodic table; intramolecular forces exist within the molecules of all covalent compounds e.g. water (H20)

Classifying Intermolecular Forces

1. H2O (oxygen disperses) - Dispersion Force

2. CH4 (high dispersion) - Dispersion Force

3. HCl (high attraction) - Dipole-dipole interaction

4. Mg (positive interaction) - ion-induced dipole interaction

5. C2H2 - dispersion force

6. K+- ion-induced dipole interaction

Properties of Liquids

1. Surface Tension- tension of the surface film of a liquid caused by the attraction of the particle on the surface layer by the bulk of the liquid, which tends to minimize the surface area

• amount of energy needed to conquer forces between molecules of the liquid’s surface and increase its surface area

• Spherical shape encloses the greatest volume of matter with the least amount of surface area

1. Cohesion- attraction between liquid and liquid

2. Adhesion- attraction between solid and liquid

2. Viscosity- the more viscous a liquid substance is, the greater the resistance to flow; e.g. a less viscous magma will extrude/ spread easily while highly viscous magma will need more force through a vent

• The viscosity of a substance depends on the intermolecular force that holds its molecules together

3. Vapor Pressure- created by faster molecules that break away from the liquid or solid and enter the gas phase

• It is expected that vapor pressure will increase with the temperature; substances with high vapor pressure are said to be volatile

Molar Heat of Vaporization & Boiling Point

• The relationship between vapor pressure and strength of intermolecular forces is consistent with the trends in two other properties of liquids, the enthalpy or molar heat of vaporization, and the boiling point of the liquid. The molar heat of vaporization (ΔHvap) is the energy required to vaporize 1 mole of a liquid at a given temperature. H is the symbol for enthalpy, which means heat content at a given standard condition.

Structure and Properties of Water

• exhibits hydrogen bonding

Density- varies with temperature (the higher the temperature, the less dense an object becomes, and vice versa). However, water has a unique property in terms of density. Its hydrogen bonds make solid ice less dense than liquid water and allow ice to float.

Water molecules form hydrogen bonds, giving tetrahedral (tetra - four, hedron - face) structuring held by four neighboring molecules

• Has boiling point of 100℃

• Above 4℃, thermal expansion will occur causing the density of water to increase

• Even with the same mass, cold water is more dense while hot water is less dense. The warmer it is, the lower the mass.

Formula for Mass, Density, & Volume: 

m = d v

d = m / v

v = m / d

Types and Properties of Solids- classified into arrangement of particles

1. Crystalline- symmetrical structure, electrostatic attraction (e.g. crystal rocks, salt (NaCl), potassium chloride (KCl), and potassium bromide (KBr)

Types of Crystalline

• Ionic

• Covalent

• Molecular

• Metallic

Amorphous/Non-crystalline- do not have a regular structure and have a more random arrangement of particles (e.g. plastics, polymer, glass)