Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23General Chemistry Topic 4:Water, Solutions, GasesObjectives: By the end of this topic, you should: 1. Be familiar with the polar nature and hydrogen-bonding properties of water molecules and how this gives rise to the structures of ice and liquid water. 2. Understand the nature of hydrophobic and hydrophilic groups.  3. Understand the process of solvation of ions 4. Understand and be able to define the terms solution, solute, solvent, and saturated solution. 5. Understand the concept of the mole, Avogadro’s Number, and why they are important. 6. Understand molarity and appreciate the significance and usefulness of this term.  7. Be able to carry out basic calculations involving molar and percent solutions and dilutions. (Note: we will work on understanding these calculations in lab as well)Suggested reading: Denniston et al., Chapter 5, pp. 187-191(180-185) and Chapter 4, pp. 128-137 (127-136). Homework problems: 4.31 (4.25), 4.36 (4.30), 4.39 (4.33), 4.45 (4.39), 4.46 (4.40), 4.48 (4.42), 4.52-4.54 (4.46-4.48)Covalent – sharing of valence electrons (molecules) - nonpolar – equal sharing of electrons - polar – unequal sharing of electrons - single (1 pair), double (2 pr), or triple (3 pr) bonds possibleH-bonds – very weak attraction between a partially positive (+) hydrogen atom and a partially negative (-) atom (usually O or N).Collectively very strong (VERY important)Ionic – attraction between oppositely charged ionsBond types:Compounds have atoms joined by chemical bonds.Bond formation involves gain, loss, or sharing of valence electrons, and is governed by the Octet Rule (fill the outer e- shell).Salts – ionic compounds: metal + nonmetal (or polyatomic ion)REVIEW - Chemical Compounds – An OverviewKnow the name and formulaClusters of atoms held together by covalent bonds - NOT electrically neutral. - atoms obey the Octet Rule Some important polyatomic ions Ion Name FormulaAmmonium NH4+Nitrate NO3-Hydronium H3O+Hydroxide OH– Acetate CH3COO– Carbonate CO3–2 Bicarbonate HCO3-Sulfate SO4–2 Phosphate PO4–3 Monohydrogen phosphate HPO4–2 Dihydrogen phosphate H2PO4– Nitrate ion NO3– Cyanide ion CN– O H-Hydroxide ion, OH- is a good exampleAmmonium ionNH4+Sulfate ionSO4-2Nitrate ionNO3-Polyatomic IonsMost organisms are mostly water, about 70% by weight.The high specific heat makes water a “heat buffer” to maintain a constant body temperature. Rates of chemical reactions that comprise life vary with temperature so keeping temperature constant is critical.Water is an excellent polar solvent. All chemical eactions in our bodies occur in water. Water is a common chemical reactant or product in living systems - hydrolysis and condensation reactions, energy storage and generation, etc.Life is aqueous - Water is a major playerStable 3-D shape of biomolecules, critical to their biological functions, mediated via interactions with solvent water (H-bonds). Hydrophobic (water-fearing) interactions among lipids make membranes.Life is aqueous - Water is a major playerOH H+ +-Dipolar nature of waterWater forms lots ofH-bonds with itselfH + - O on different water moleculesO is much more electronegativethan is H; electrons spend mostof their time around O atomunshared e- pairs;electronegativityWater is a polar molecule – a good thingThe structure of water itself is determined by H-bonding interactions among water molecules. Each water molecule participates in several H-bonds with other water molecules.Water, a very polar molecule, is a great solvent for polar molecules, and for most ionic compounds.“Like dissolves like”Molecules that can participate in the H-bonding network of water will dissolve in water.Water is a polar moleculeCrystal structure ofsolid water (ice)Structure of liquid water(almost crystalline)+= Na+-= Cl-NaClcrystalWater is a good solvent for ions, forming “solvent cages” around them, holding them in solution.hydrated ions- of O on H2Ointeracts with Na++ of H on H2Ointeracts with Cl-Solvation of ionic compounds by waterSoluble salts dissolve (separate into individual ions) in water.Insoluble salts do NOT dissolve in water; they remain as solids even when in water.Why? Ionic attractions between (+) and (-) ions in ionic compound are too strong for water to break (solvate).Solubility: the amount of solute that can be dissolved in 100 mL H2O. - varies (greatly) with different salts and molecules - generally increases with increasing temperatureSaturated solution - contains all the solute it can dissolve at a given TSoluble vs. Insoluble SaltsSome general solubility rules (FYI, not exam material): Salts that contain Na+, K+, NH4+, or NO3- are “always” soluble Salts that contain OH-, CO3-2, S-2, or PO4-3 are insoluble (unless they also contain one of the above soluble ions)Water also “solvates” or dissolves polar molecules, again forming “solvent cages” around individual molecules.Sucrose(sugar)crystalHydrophilic = water-loving - polar groups (-OH, -NH2) - ionic groups (NH3+; COO-)Solvation of polar molecules by waterMolecules that contain O, N, F, or Cl (electronegative atoms) are polar.Molecules that cannot participate in the H-bonding network of water are insoluble in water, they have NO attraction for water and will NOT dissolve.Hydrophobic interactions; interactions that hold hydrophobic molecules (or parts of molecules) together and away from water.Hydrophobic interactionsare absolutely criticalfor living systemsMembranes = cellsunstablestableHydrophobic (water-fearing) molecules are insoluble in waterMixture - a blend of two or more compounds or elements in any relative amounts.Homogeneous mixture - any small sample has the same composition/properties as any other sample taken anywhere else in the mixture.Solution - homogeneous mixture in which the particles of both solvent and solute are the size of atoms, ions, or molecules.Colloidal dispersion - homogeneous mixture in which the dispersed particles are large cluster of ions, molecules, or macromolecules, e.g., proteins in blood, mayonnaise, smoke.Suspensions - dispersed or suspended particles are > 1000 nanometers (1 m or 0.001 mm) in average diameter, e.g., blood is a