Kinetic Molecular Model and Intermolecular Forces

• Kinetic Molecular Theory explains the properties of gas, solids, and liquids in terms of intermolecular forces of attraction and the kinetic energy of the individual particles.
• All matter is made of tiny particles. These particles are in constant motion.
• The speed of particles is proportional to temperature.
• Solids, liquids, and gases differ in distances between particles, freedom of motion of particles, and the extent to which the particles interact.
• Solid's Volume/Shape is fixed, regardless of size and the shape of the container
• Solid's Compressibility is Almost incompressible
• Solid's Density is High
• Solid's motion, Vibration in place
• Liquid's Volume/Shape is Fixed volume;assumes The shape of the occupied part ofcontainer.
• Liquid's Compressibility is Slightly compressible but cannot be easily compressed.
• Liquid's Density is High
• Liquid's motion is random, medium speed, limited distances
• Gas Volume/Shape, assumes volume and shape of container.
• Gas Compressibility is Easy to compress
• Gas density is low.
• Gas motion is random, fast, cover large distances
• Liquids and solids are in condensed states compared to gases.
• Based on KMT the Molecules of Solids are closely packed, arranged in highly organized order. Always in constant motion. Vibrating around fixed locations. Held together by strong intermolecular forces.
• Based on KMT the Molecules of Liquids are held together by attractive intermolecular forces. Close together with little space between molecules. With higher collision rate than gases. In constant motion,move/slide one past another freely so liquid can flow.
• A force of attraction is any type of force that causes objects to come together, even if those objects are not close to or touching each other.
• Types of Forces of Attraction: INTRAMOLECULAR are attractive forces between atoms in a molecule.
• Types of Forces of Attraction: INTERMOLECULAR are attractive forces between molecules.
• Generally, intermolecular forces are weaker than intramolecular forces.
• Intramolecular Forces: Metallic Bond consists of positive ions and a sea of electrons, which is free to move about among the ions.

  
  

  Ex: Fe, Mg, Li
• Intramolecular Forces: Ionic Bond electrostatic attraction between two oppositely charged ion.

  
  

  Ex: NaCl, MgO
• Intramolecular Forces: Covalent Bond a bond that involvesthe sharing of electrons to form electron pairs between atoms.

  Ex: H₂, CO₂, H₂O
• Covalent Bond (Bond Polarity): Polar covalent compounds with uneven sharing of electrons.
• Covalent Bond (Bond Polarity): Non-Polar covalent compounds with equal sharing of electrons.
• Ways to Determine the Bond Polarity: Difference in Electronegativity is the difference between the electronegativity of the atoms in a bond.
• Ways to Determine the Bond Polarity: Dipole Moment the product of the charges at one center multiplied to the distance between the positive and the negative centers.
• If the electronegativity difference has a value of:0 NON-POLAR COVALENT0.1 – 1.8 POLAR COVALENT

  >1.9 IONIC
• Electronegativity The ability of an atom to attract itself to the electrons in a chemical bond.
• Elements with high electronegativity have a greater tendency to attract electrons than the elements with low electronegativity
• Dipole moments occur when there is a separation of charge. A quantitative measure of the polarity of a bond.
• Dipole moment can be predicted using the difference in electronegativity of the atoms in a bond. The higher the difference in electronegativity the larger the dipole moment.
• The shift of electron density is symbolized by placing a crossed arrow.
• Intermolecular Forces: Ion- Dipole Bond attractive forces between an ion and a polar molecule.Ex: H₂O and Na +
• Dipole refers to a bond or molecule whose ends have opposite charges.
• Van der Waals Forces are intermolecular forces where the distance affects their strength.
• Van der Waals Forces are weaker than intramolecular forces.