Water’s Unique Properties There are strong forces of attraction between molecules of water. Hydrogen bonds Water is a polar molecule Water is amphoteric (can act as both acid & base) Water exists as a liquid over a wide temp range. Liquid water changes temperature slowly. High specific heat Liquid water can dissolve a variety of compounds. Water expands when it freezes.

Attraction Between Molecules There are strong forces of attraction between molecules of water. Hydrogen bonds Result in many distinctive properties

Liquid state Exists in liquid state over wide range of temperatures: 32° F to 212° F This is important because most biological processes require liquid water.

Unique Role of Water in Biological Systems It makes up about 70% of the human body It takes up about 71% of the Earth’s surface.

Water is critical to virtually all cellular function – Metabolism – Diffusion – Osmosis – Transport – Reproduction – Lubricant – Volume – Cellular respiration: C 6 H 12 O 6 + O 2 → CO 2 + H 2 O + energy – Photosynthesis: CO 2 + H 2 O + sunlight → C 6 H 12 O 6 + O 2 Key Role in Biological Systems

High Heat Capacity Water warms & cools slower than surrounding land Helps moderate earth’s climate

Universal Solvent: Water can dissolve many substances. Carry nutrients flush wastes distribute particles facilitate other cycles Unfortunately, it can become polluted by water- soluble wastes & transport wastes thru ecosystem

Expands When Frozen Ice has a lower density than liquid water. Thus, ice floats on water. One of the only exceptions to thermal expansion

Surface tension Surface behaves like an elastic membrane Cohesion – water molecules stick to each other

Capillary action Long narrow columns of water rise through roots to leaves Adhesion – water molecules stick to other surface

What are solutions? Homogeneous mixtures containing 2 or more substances called the solute and the solvent. Solute When you look at a solution it is impossible to tell the solute from the solvent Solvent

Solutions Solute- what is being dissolved Solvent- the dissolving medium (causes the dissolving) Solution- the resulting homogeneous mixture Aqueous Solution - water is solvent Dilution – adding more solvent = less concentrated

Universal Solvent Water is the most common solvent among liquid solutions H 2 O is polar, having a slightly positive charge on the hydrogen end and negative charge on the oxygen end. Because water is polar it dissolve other polar and ionic compounds

Dissolution or Solvation of Solid Solute = Dissolving Happens only on the surface Water molecules surround, attract, and pull ions or molecules into solution

Like dissolves Like Polar substances dissolve polar Nonpolar substances dissolve nonpolar Water is polar…which of the above will dissolve in H 2 O Glucose Mineral Oil Isopropyl Alcohol

Solubility Solubility is maximum amount of solute that will dissolve in solvent at a set of condition Soluble - A substance that dissolves in a solvent ex. Salt and water Insoluble - A substance that does not dissolve ex. Sand and water Miscible – 2 liquids that are soluble Ex. Alcohol and water Immiscible – 2 liquids that aren’t soluble Oil and Water

Factors Affecting Solubility & Rate of Dissolution (Dissolving) 1.Nature of Solute / Solvent 1.Nature of Solute / Solvent. - Like dissolves like Polar dissolves polar; nonpolar dissolves nonpolar 2. Temperature - affects velocity of particles 3. Pressure 4. Agitation = Stirring – disperses particles 5.Surface Area: crushing increases surface area on which dissolving can occur Sugar cubes vs Granulated sugar

Factors Affecting Solubility & Rate of Dissolution (Dissolving) Solid Solute in Liquid solvent Gas Solute in Liquid solvent Ex. Sugar in TeaEx. CO 2 bubbles in soda Temperature ↑ Pressure ↑ Agitation – ↑ Stirring Surface Area – ↑ Crush ↑↓ N/A ↑ ↑ ↓ ↑ N/A – can’t crush a gas!

General Solubility Rules Use STAAR Chart to determine Which Ionic compounds are soluble and insoluble NaNO 3 AgCl Be 3 (PO 4 ) 2 Na 3 PO 4 soluble insoluble soluble insoluble

Types of Solutions 1.Electrolytes – ionic compounds dissolve into ions conducts electric current the more ions → stronger current 2.Nonelectrolytes – molecular compounds: stay molecules in solution no ions → do not conduct current

Nonelectrolyte Weak electrolyte Strong electrolyte

Electrolytes in the Body  Carry messages to and from the brain as electrical signals  Maintain cellular function with the correct concentrations electrolytes

Types of Solutions 1.Saturated Solution: Full 2.Unsaturated Solution: not full 3.Supersaturated Solution: overly Full, crystals will form when disturbed

Saturated Solution Contains the maximum amount of dissolved solute for a given amount of solute at at specific temperature No more will dissolve Will be a point on the line of a Solubility Graph Ex. NaClO 3 at 40°

Unsaturated solution contains less dissolved solute for a given temperature and pressure than a saturated solution More can be dissolved Will be a point under the line on graph Ex. NaClO 3 at 40°

Supersaturated solution contains more dissolved solute than a saturated solution at the same temperature Contains more than it should Will precipitate if disturbed Will be a point above the line Ex. NaClO 3 at 40°

Saturated solution to supersaturated solution 3bKIOkcmk&feature=fvwp 3bKIOkcmk&feature=fvwp

Solubility Graph Determine type of solution: 30 grams of NaCl at 10°C Unsaturated 30 grams of K 2 Cr 2 O 7 at 50°C Saturated 50 grams of KCl at 40°C Supersaturated

Concentration of Solute The amount of solute in a solution is given by its concentration. Molarity (M) = moles solute Liters of solution EX: A liter of solution containing 0.1 mole of solute is a 0.1 M solution

A 100.5ml intravenous, IV, solution contains 5.10g of glucose (C 6 H 12 O 6 ). What is the molarity of this solution? Mass of solute = 5.10g C 6 H 12 O 6 Volume of solution = 100.5ml Molarity = ? 1 st – calculate the # of moles g C 6 H 12 O 6 2 nd – convert milliliters into liters (1000 ml = 1 L) 100.5ml = ______________L rd – use formula to solve Molarity = Moles of solute = Liters of solution = 0.282M = mol C 6 H 12 O g C 6 H 12 O 6 1 mole C 6 H 12 O 6

V 1 M 1 = V 2 M 2 Because total # of moles of solute does not change during dilution: moles in stock solution = moles after dilution, so: Molarity decreases as Volume increases Dilution Quite often, however, solutions are prepared by diluting a more concentrated solution. For example, if you needed a one molar solution you could start with a six molar solution and dilute it. The number of moles of solute stays the same. You have simply increased the amount of solvent in the solution

What volume of a 3.0 M KI stock solution would you use to make a 0.50 L of a 1.5M KI solution??? 1 st : Make a list M 1 = 3.0 M V 1 = ? V 2 = 0.50 L M 2 = 1.5 M Then plug into formula: V 1 M 1 = V 2 M 2 V 1 (3.0) = 0.50(1.5) And solve for V 1 = 0.50(1.5) 3.0 = 0.25 L