Gen Chem 2 Departmental Reviewer PDF

GEN CHEM 2 DEPARTMENTAL REVIEWER PROPERTIES OF LIQUID AND INTERMOLECULAR FORCES Viscosity - a measure of a fluid’s Fluid - Gas or liquid; Substance resistance to flow. The greater the that can flow. viscosity, the slower the liquid...

GEN CHEM 2 DEPARTMENTAL REVIEWER PROPERTIES OF LIQUID AND INTERMOLECULAR FORCES Viscosity - a measure of a fluid’s Fluid - Gas or liquid; Substance resistance to flow. The greater the that can flow. viscosity, the slower the liquid flows. Surface Tension - the measure of the elastic force in the surface of a Viscosity is expressed in units of liquid. It is the amount of energy centipoise. required to stretch or increase the surface of a liquid by a unit area. It is Water Viscosity - 1 centipoise or like an elastic film or “skin”. 0.001 Pa/s at 20°C. Molecules within a liquid are The more Hydrogen bonding (OH), pulled in all directions by the higher the viscosity. intermolecular force while molecules at the surface are pulled The larger the molecule, even downwards and sideways by other nonpolar, the stronger the molecules. intermolecular forces and viscosity. Liquids with strong intermolecular force = high surface tension Liquids that have strong intermolecular forces have higher Capillary Action - the tendency of viscosities than those that have a liquid to rise in narrow tubes or weak intermolecular forces. be drawn into small openings such as those between grains of a Vapor - A gaseous substance that rock. Capillary action, also known as exist naturally as a liquid or capillarity, is a result of solid at normal temperature. intermolecular attraction between the liquid and solid materials. Vaporization - The change of phase from liquid to vapor (gaseous phase). 2 TYPES OF CAPILLARY ACTION: Cohesion - the intermolecular attraction between like molecules Vapor pressure of a liquid - the (the liquid molecules). rate of condensation of the gas Adhesion - attraction between becomes equal to the rate of unlike molecules (such as those in evaporation of the liquid = water and in the particles that make EQUILIBRIUM up the glass tube). liquid ⇋ vapor (gas) Meniscus - the curved surface of a liquid in a container. The curve can The equilibrium vapor pressure - be either concave or convex. is the maximum vapor pressure of - Concave: If adhesion is stronger a liquid at a given temperature and than cohesion, curved downwards that it is constant at a constant at the edges. temperature. It increases with - Convex: If cohesion is stronger temperature. than adhesion, curved upwards at the edges. GEN CHEM 2 DEPARTMENTAL REVIEWER The greater the number of gaseous Crystal or crystalline solid - A particles, the greater the pressure solid material whose exerted by the gas. components, such as atoms, molecules or ions, are arranged in a As temperature increases, the vapor highly ordered microscopic pressure also increase (directly structure. proportional) Ion - An atom or group of atoms The stronger the intermolecular force that has a net positive or of attraction, the lower the vapor negative charge. pressure. Ionic crystal - A solid that consists Boiling point - the temperature at of positively and negatively which the liquid converts into a charged ions held together by gas. The boiling point is the electrostatic forces. temperature at which the vapor pressure of a liquid is equal to the Electrostatic bonding - The external pressure. attraction between oppositely charged ions in a chemical The Normal boiling point = 1 atm. compound. The normal boiling point of water Ionic bond - The electrostatic force =100°C. that holds ions together in an ionic compound. The boiling point is related to molar heat of vaporization: the higher Network solid or covalent network ΔHvap , the higher the boiling crystal - A solid that may be a point chemical compound (or element) in which atoms are bonded by Molar heat of vaporization (ΔHvap) covalent bonds in a continuous - the energy required to vaporize network extending throughout the 1 mole of a liquid at a given material. temperature. Molecular crystal - A solid H = enthalpy, which means heat composed of molecules held content at a given standard condition. together by van der Waals forces (dispersion Type of energy: kinetic & heat force, dipole- dipole attraction, hydrogen bonding). The higher the (ΔHvap), the boiling point also increases Covalent bond - A bond in which one or more pairs of electrons are If intermolecular force is strong, shared molar heat & boiling point must also be high. Crystal lattice - The regular repeating structure of a crystalline PROPERTIES OF SOLID AND solid. INTERMOLECULAR FORCES Unit cell - The smallest subunit of a crystal lattice that can be GEN CHEM 2 DEPARTMENTAL REVIEWER repeated over and over to make the conductor, Good heat conductor, entire crystal. Malleable and conductor, Lustrous. 2. Ionic crystals - made of ions 2 TYPES OF SOLID: (cations & anions) that forms a - crystalline solid strong electrostatic interaction. Hard - amorphous solid and of high melting points. (Ex: Typical salts; NaCl, Ca(No3)2) DISTINCT FEATURES: *Observed property: Hard, high 1. Arrangement melting point, poor electrical - Crystalline: fixed geometric conductor in the solid state, good pattern or lattices. Regular & electrical conductor in the molten repeating. Ex. Sodium chloride state, brittle. (NaCl), Copper sulfate (CuSO4 ), and sugar 3. Molecular crystals - made of (C12H22O11) atoms like noble gas or molecules. (Ex: Argon, Ar; mthane, - Amorphous: random orientation. CH4;sucrose, C12H22O11; Dry ice) Considered super-cooled liquids.Ex. *Observed property: Soft, low are glass, plastic, coal, and rubber. melting point, poor electrical conductor in the solid and molten 2. Behavior when heated state, poor heat conductor, brittle. - Crystalline: repeating units called crystal lattices. The crystals are all 4. Covalent Network crystals - broken by the same amount of made of atoms in covalent bonds energy, and also becomes liquid at (shares electron to its nearest the same time at the specific neighbor). There are no individual temperature. molecules and the entire crystal -Amorphous: wide range of may be considered one very large temperature. molecule. (Ex: Diamond, C; quartz, SiO2) CRYSTALLINE SOLID: *Ovserved property: Hard, very - made of crystal lattices (regular high melting point, poor electrical repeating structure). conductor in the solud and molten state, poor heat conductor, brittle. - xray diffraction: Technique to determine the atomic & molecular structure of a crystal. Atoms cause beams of incident x-ray to diffract into many specific directions. TYPES OF CRYSTALLINE: 1. Metalic crystals - electrostatic interactions between cation and delocalized electrons. Metallic bonds = sea of electrons. (Ex: iron, silver, gold, etc) *Observed property: Dense, High melting point, Good electrical