Kinetic Molecular Model of Solids and Liquids PDF

Kinetic Molecular Model of Solids and Liquids Lesson 1.1  kinetic molecular theory explains the states of matter and is based on the idea that matter is composed of tiny particles that are always in motion. This theory helps explain observable properties and behavior...

Kinetic Molecular Model of Solids and Liquids Lesson 1.1  kinetic molecular theory explains the states of matter and is based on the idea that matter is composed of tiny particles that are always in motion. This theory helps explain observable properties and behaviors of solids, liquids, and gases.  kinetic molecular model explains the properties of solids and liquids in terms of the intermolecular forces of attraction and the kinetic energy of the individual particles. Intermolecular forces Kinetic energy (attractive forces between (the energy that comes from neighboring particles of one motion) keeps the particles at or more substances) pull the a distance and/or moving particles together around. It is dependent on the temperature of the substance.. kinetic molecular model To put this model in another perspective, consider a few drops of blue food color added to a glass of water. The blue food color slowly goes down the glass of water, spreads out, and ultimately colors the entire water blue. This happens because both the particles of water and the food color are constantly moving due to their kinetic energy. Kinetic molecular model of the liquid state this model explains how liquids behave 01 Definite Volume: fixed. Does not vary. They cannot expand to fill a container 02 Fluidity: Liquids can flow, adjusting to the shape of their containers, because their molecules are free to move. 03 Density: The molecules of a liquid are packed relatively close together. Consequently, liquids are much denser than gases. 04 intermolecular force: The particles of liquid are held close together by strong intermolecular attractive forces, but not strong enough to keep them in a rigid position. 05 Slightly compressible: much less compressible than gases because particles are closer together 06 Dissolving Ability: liquids can dissolve solids, liquids, and gases 07 Ability to Diffuse: mix with other liquids due to the constant motion of particles. Note: liquids diffuse more slowly than gases 08 Tendency to Evaporate and Boil: Vaporization is the liquid to gas phase change 09 Tendency to Solidify: Freezing is the liquid to solid phase change  Questions: ❑ Why are liquids denser than gases? ▪ Molecules are closer together so more molecules in a given area ❑ Why are liquids harder to compress than gases? ▪ Same as above – molecules are closer ❑ Why do liquids diffuse slower than gases? ▪ Particles are not moving as fast as gases ❑ Can a liquid boil without increasing the temperature? How? ▪ Yes – lower the atmospheric pressure Kinetic molecular model of the solid state this model explains how solids behave 01 Definite shape and volume: solids maintain a definite shape without a container. Volume is constant due to closely packed particles. 02 Non-fluid: particles cannot flow because particles are held in relatively fixed positions. 03 High Density: solids are packed more closely than that of a liquid or gas. 04 intermolecular force: the intermolecular attractive forces between their particles are stronger than those in liquids and gases, enough to keep the solids rigid. 05 Incompressible: particles are packed so close together there is virtually no space between them Characteristics of Solids and Liquids Solids Liquids Properties ▪ Have definite volume ▪ Have definite volume but and shape no definite shape ▪ Do not flow ▪ Flow and take the shape of ▪ Virtually incompressible their container ▪ Expand when heated, but ▪ Very difficult to compress to a lesser extent than ▪ Slightly expand when liquids and gases heated Particles ▪ Strongly attracted to each Weakly attracted to each other other; break their ▪ Vibrate in fixed positions interaction easily ▪ Vibrate faster when Move more freely than heated those in solids; slide past one another Move faster when heated Intermolecular forces of attraction Lesson 1.2  Intermolecular forces – occur between molecules Intramolecular forces – occur inside the molecules (bonds)  Intermolecular forces of attraction The Intermolecular forces of attraction in a pure substance include dipole-dipole, hydrogen bonding, ion-dipole, and London dispersion forces. Dipole-dipole and London dispersion forces are collectively known as van der Waals forces.  Dipole-Dipole Forces Electronegativity- the tendency of an atom to attract electrons The more electronegative atom pulls the electron H Cl toward itself and gains a partial negative charge. Dipole- opposite charges (positive and negative)  Dipole-Dipole Forces Chlorine atoms pull the shared pair of electrons equally Cl Cl Electrons remain in between Not a dipole Dipole-Dipole Forces Polar molecules attract each other when unlike charges are close together and repel each other when like charges are close together Hydrogen Bond A hydrogen bond is a special type of dipole- dipole interaction that exists only in molecules that contain a hydrogen atom bonded to a small, highly electronegative atom such as N, O, or F.  Hydrogen Bonds The more electronegative atom pulls the electron toward itself and gains a relatively large partial negative charge. In turn, the hydrogen acquires a similarly large partial positive charge that strongly attracts the partial negative charge of a neighboring electronegative atom.  Hydrogen Bonds Note that unlike covalent bonding, where electrons are involved and shared between atoms, the hydrogen bond is not a real chemical bond that participated in by electrons. A covalent bond is a type of intramolecular force of attraction, while hydrogen bond is intermolecular in nature. Ion-Dipole Forces Ion-dipole interaction Ion-dipole interaction Ion-Dipole Forces  Ion-Dipole Forces Ion-dipole attraction becomes stronger as the charge of the ion increases.  London Dispersion Forces London dispersion forces, or simply dispersion forces, are intermolecular forces of attraction that exist between all atoms and molecules. Moreover, these are the only forces acting in nonpolar molecules. Nevertheless, the electrons have some freedom to move about the molecule; therefore, at any instance, the molecule momentarily acquires a non-uniform electron density resulting in a temporary dipole (also called instantaneous dipole). This dipole can then induce dipoles in neighboring molecules. Therefore, the London dispersion forces are attractions between an instantaneous dipole and an induced dipole. neutral atom temporary dipole temporary neutral atom induced dipole dipole temporary induced dipole dipole London Dispersion Force London Dispersion Forces The size of a molecule can affect the London dispersion force between two molecules. The bigger the molecule, the stronger the attraction between two molecules. As an example, between helium and argon, two argon atoms will have greater London dispersion force because they are bigger than helium atoms.