2. Properties of Liquids Surface tension is the resistance of a liquid to an increase in its surface area. Strong intermolecular forces (polar molecules) High surface tension To increase a liquid’s surface area, molecules must move from the interior of the liquid to the surface. Requires energy since intermolecular forces must be overcome.

3. Properties of Liquids Cohesion is the intermolecular attraction between like molecules Adhesion is an attraction between unlike molecules Adhesion Cohesion attracted to glass attracted to each other Capillary action – spontaneous rising of a liquid in a narrow tube.

4. Properties of Liquids Viscosity is a measure of a liquid’s resistance to flow. Strong intermolecular forces High viscosity

6. Two categories Amorphous solids – considerable disorder in their structures. Crystalline solids – highly regular arrangement of their components. Lattice – three dimensional system of points designating the positions of the components that make up the crystal. Unit Cell – smallest repeating unit of a lattice. At lattice points: Atoms Molecules Ions Unit cells in 3 dimensions Unit Cell lattice point

7. Types of Crystalline Solids Ionic Solids – Ion-Ion interactions are the strongest (including the “intermolecular forces” (H bonding, etc.) Lattice points occupied by ions Held together by electrostatic attraction Hard, brittle, high melting point Poor conductor of heat and electricity CsClZnSCaF 2

8. Types of Crystalline Solids Network Atomic Solids – Stronger than IM forces but generally weaker than ion-ion Lattice points occupied by atoms Held together by covalent bonds Hard, high melting point Poor conductor of heat and electricity diamond graphite carbon atoms

9. Types of Crystalline Solids Metallic Atomic Solid – Typically weaker than covalent, but can be in the low end of covalent Lattice points occupied by metal atoms Held together by metallic bonds Soft to hard, low to high melting point Good conductors of heat and electricity Cross Section of a Metallic Crystal nucleus & inner shell e - mobile “sea” of e -

10. Types of Crystalline Solids Molecular Crystals Lattice points occupied by molecules Held together by intermolecular forces Soft, low melting point Poor conductor of heat and electricity Sulfur crystals Phosphorus crystals