 Triatomic molecule  Contains covalent bonds  Includes partial positive and partial negative charges  Where do these charges come from?

 Water is a polar molecule. WHY??

 Attraction from dipole interactions. ◦ The negative end of one molecule attracts the positive end of another molecule.

 Hydrogen bonds occur from intermolecular attractions between water molecules  Other properties affected by hydrogen bonding ◦ Surface tension and Vapor Pressure

 inward force, or pull, that tends to minimize the surface area of a liquid  Water has higher surface tension than other liquids ◦ Why ? ◦ Water molecules at the surface can not form hydrogen bonds with air therefore the water molecules will turn inward to forma skin

 Surface tension makes it possible for this water strider to walk on water.

 A surfactant is any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension  Examples: ◦ Soaps and Detergents ◦ Soaps and detergents will reduce the surface area and cause the water to collapse

 Results from molecules escaping the surface of a liquid and entering the vapor phase ◦ Remember it is the measurement of the force exerted by gas above a liquid in a sealed container  Hydrogen bonding between water molecules also explains water’s unusually low vapor pressure. Because hydrogen bonds hold water molecules to one another, the tendency of these molecules to escape is low, and evaporation is slow.

 As water begins to cool, it behaves initially like a typical liquid. It contracts slightly and its density gradually increases. When the temperature of the water falls below 4˚C, the density of water starts to decrease.

 Hydrogen bonds hold the water molecules in place in the solid phase.  Honeycomb  When ice melts, the framework collapses, and the water molecules pack closer together, making liquid water more dense than ice

 An aqueous solution is water that contains dissolved substances.  In a solution, the dissolving medium is the solvent.  In a solution, the dissolved particles are the solute.  Solvents and solutes may be gases, liquids, or solids.  Solute particles can be atoms, ions, or molecules.

 Filtration will not work bc both the solvent and solute will pass through the filter paper

 As individual solute ions break away from the crystal, the negatively and positively charged ions become surrounded by solvent molecules, and the ionic crystal dissolves

 The process by which the positive and negative ions of an ionic solid become surrounded by solvent molecules is called solvation.

 Polar solvents such as water dissolve ionic compounds and polar compounds.  Nonpolar solvents such as gasoline dissolve nonpolar compounds.

 An electrolyte is a compound that conducts an electric current when it is in an aqueous solution or in the molten state.  ALL IONIC COMPOUNDS are Electrolytes bc they dissociate into their ions

 The bright glow shows that sodium chloride is a strong electrolyte because nearly all the dissolved sodium chloride exists as separate Na + and Cl – ions.

 A weak electrolyte conducts electricity poorly because only a fraction of the solute in the solution exists as ions

 A compound that does not conduct an electric current in either aqueous solution or the molten state is called a nonelectrolyte

 Suspension-particles will settle out upon standing ◦ Example: Clay and water Flour and water

 Particle Size  Suspensions have large particle size Diameter greater than 1000 nm  Solutions ◦ Diameter usually 1nm

 Suspensions are heterogenous because at least two substances can be clearly identified.  Can be separated by filtration

 A colloid is a heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm. The particles in a colloid are spread throughout the dispersion medium.  Larger particles than solution and smaller than suspension particles

 An emulsion is a colloidal dispersion of a liquid in a liquid. An emulsifying agent is essential for the formation of an emulsion and for maintaining the emulsion’s stability.  Mayonnaise is heterogeneous mixture of oil and vinegar. Such a mixture would quickly separate without the presence of egg yolk, which is the emulsifying agent.