Chem 331 Phases of Substances and solutions Kinetic theory The kinetic particle theory explains the properties of the different states of matter. The particles in solids, liquids and gases have different amounts of energy. They are arranged differently and move in different ways. This table summarizes the arrangement and movement of the particles in solids, liquids and gases, and shows simple diagrams of the arrangement of the particles that you should be able to recognize. Diagram of particle arrangement and movement Solid Liquid Gas Arrangement of particles close together regular pattern close together random far apart random movement of particles vibrate about a fixed position move around each other move quickly in any direction diagram Solids The table shows some of the properties of solids and why they are like this. Property of solids Why they are like this They have a fixed shape and cannot flow The particles cannot move from place to place They cannot be compressed or squashed The particles are close together and have no space to move into Liquids Some of the properties of liquids and why they are like this Property of liquids Why they are like this They flow and take the shape of their container The particles can move around each other
o Dipole-induced dipole forces: The field of a permanent induces a dipole in a non-polar atom or molecule. o Dispersion force: Due to charge fluctuations of the atoms there is an instantaneous displacement of the center of positive charge against the center of the negative charge. Thus at a certain moment a dipole exists and induces a dipole in another atom. Therefore non-polar atoms (e.g. neon) or molecules attract each other. Table 1: Short Range Interaction Forces Nature of Bond Type of Force Energy (kcal/mol) Distance Ionic bond Coulombic force 180 (NaCl) 240 (LiF) 2.8 Å 2.0 Å Covalent bond Electrostatic force (wave function overlap) 170 (Diamond) 283 (SiC) N/A N/A Metallic bond free valency electron sea interaction (sometimes also partially covalent (e.g., Fe and W) 26 (Na) 96 (Fe) 210 (W) 4.3 Å 2.9 Å 3.1 Å Hydrogen Bond a strong type of directional dipole-dipole interaction 7 (HF) Van der Waals (i) dipole-dipole force (ii) dipole-induced dipole force (iii) dispersion forces (charge fluctuation) 2.4 (CH4) significant in the range of a few Å to hundreds of Å Types of intermolecular forces
trichloromethane/propanone and nitric acid/water mixtures. Phase diagrams showing a minimum (figure) indicate that the mixture is destabilized relative to the ideal solution, A-B interactions then being unfavourable. For such mixtures GE is positive (less favourable to mixing than ideal), and there may be contributions from both enthalpy and entropy effects. Examples include dioxane/water and ethanol/water mixtures. The system shown in the figure below is also azeotropic, but shows its azeotropy in a different way. Suppose we start with a mixture of composition a1, and follow the changes in the composition of the vapour that raises trough a fractionatimg column. The mixture boils at a2 to give a vapour of composition a'2. This vapour condenses in the column to a liquid of the same composition (a3). That liquid reaches equilibrium with its vapour at a3', which condenses higher up the tube to give a liquid of the same composition, which we now call a4. The fractionation therefore shifts the vapour towards the azeotropic composition at b, but not beyond, and the azeotropic vapour emerges from the top of the column. An example is ethanol/water, which boils