CHEMISTRY GEN CHEM 2 Kinetic-Molecular-Model.pptx

Kinetic molecular model GEN CHEM 2

1. KINETIC MOLECULAR MODEL

2. KINETIC THEORY Kinetic Theory states that the tiny particles in all forms of matter are in constant motion. Kinetic refers to motion Helps you understand the behavior of solid, liquid, and gas atoms/molecules as well as the physical properties Provides a model behavior based off three principals 3 Principles of Kinetic Theory All matter is made of tiny particles (atoms) These particles are in constant motion When particles collide with each other or the container, the collisions are perfectly elastic (no energy is lost)

3. Kinetic-Theory Description of the Solid State Lower kinetic energy , less motion , more packed particles , and higher intermolecular forces (IMF) Intermolecular forces between particles are therefore much more effective in solids. These hold particles of a solid in relatively fixed positions, with only vibrational movement. Solids are more ordered than liquids and gases.

4. SOLIDS Particles are tightly packed and close together Particles do move but not very much Definite shape and definite volume (because particles are packed closely and do not move) Most solids are crystals Crystals are made of unit cells (repeating patterns) The shape of a crystal reflects the arrangement of the particles within the solid

5. Properties of Solids and the Particle Model – Definite shape and volume - solids maintain a definite shape without a container. Volume is constant due to closely packed particles. Non-fluid - particles can’t flow because particles are held in relatively fixed positions. Definite melting point - The temperature at which the kinetic energy of the particles are able to overcome the attractive forces holding them together in fixed positions (crystalline only) High Density- solids are packed more closely than that of a liquid or gas. Incompressible - particles are packed so close together there is virtually no space between them Slow Diffusion – much slower than liquids due to the high IMF’s between particles.

6. SOLIDS Unit cells put together make a crystal lattice (skeleton for the crystal) Crystals are classified into seven crystal systems: cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, rhombohedral Unit cell  crystal lattice  solid

7. SOLIDS Amorphous Solid: A solid with no defined shape (not a crystal) A solid that lacks an ordered internal structure Examples: Clay, PlayDoh , Rubber, Glass, Plastic, Asphalt Allotropes: Solids that appear in more than one form 2 or more different molecular forms of the same element in the same physical state (have different properties) Example: Carbon Powder = Graphite Pencil “lead” = graphite Hard solid = diamond

8. SOLIDS www.ohsu.edu/research/sbh/resultsimages/crystalvsglass.gif

9. SOLIDS Allotropes of Carbon: a) diamond b) Graphite c) lonsdaleite, d)buckminsterfullerene (buckyball) e) C540 f) C70 g) amorphous carbon h) single-walled (buckytube) www.wikipedia.org

10. LIQUIDS Particles are spread apart Particles move slowly through a container No definite shape but do have a definite volume Flow from one container to another Viscosity – resistance of a liquid to flowing Honey – high viscosity Water – low viscosity chemed.chem.purdue.edu/.../graphics

11. Kinetic Theory Description of the Liquid State According to the kinetic theory, motion of liquid particles can be described as . . . a form of matter that has a definite volume and takes the shape of its container. Kinetic-Theory Description of the Liquid State Particles in a liquid are in  constant motion however, the particles in a liquid are closer together than the particles in a gas are. Therefore, the attractive forces between particles in a liquid are more effective than those between particles in a gas. This attraction is caused by intermolecular forces. the particles are not bound together in fixed positions.

12. Properties of Liquids and the Particles Model – define each property Properties of Fluids Definite Volume - fixed. Does not vary. They cannot expand to fill a container Fluidity – ability to flow and take shape of container Relative High Density- close arrangement of particles (compared to a gas) making mass/volume ratio higher. Incompressible – much less compressible than gases b/c particles are closer together Dissolving Ability- liquids can dissolve solids, liquids, and gases Ability to Diffuse – mix with other liquids due to constant motion of particles Surface Tension – results from attractive forces between particles on a liquid’s surface. a force that pulls adjacent parts of the liquid’s surface together, thereby decreasing surface area Tendency to Evaporate and Boil - Vaporization is the liquid to gas phase change Tendency to Solidify - Freezing is the liquid to solid phase change