Presentation on theme: "The Chemistry of Life: Properties of Water"— Presentation transcript:
1 The Chemistry of Life: Properties of Water BiologyMs. Haut
2 Properties of Water Cohesive nature of water Ability to moderate temperatureUnusual phase changesVersatile solvent
3 THE PROPERTIES OF WATER 1. Cohesion of WaterWater is a polar molecule, electrons are shared unequallyCohesion is the ability of water molecules to attach to other water moleculesAttach by hydrogen bonds
4 In a water molecule, oxygen exerts a stronger pull on the shared electrons than hydrogen This makes the oxygen end of the molecule slightly negatively chargedThe hydrogen end of the molecule is slightly positively chargedWater is therefore a polar molecule(–)(–)OHH(+)(+)Figure 2.9
5 H+ atom is covalently bonded to the oxygen via a shared pair of electrons. Oxygen is an "electronegative" or electron "loving" atom compared with hydrogen"polar" molecule, meaning that there is an uneven distribution of electron densityThis attraction forms weak bonds called hydrogen bonds
6 Surface TensionThe cohesion of water molecules at the surface of a body of water
7 Due to hydrogen bonding, water molecules can move from a plant’s roots to its leaves Insects can walk on water due to surface tension created by cohesive water moleculesWater Spider
8 Adhesion Water can also be attracted to other materials. Water can also be attracted to other materials.
9 Capillary ActionWhen one water molecule moves closer to the straw molecules the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw.WaterMercury
10 Plant Transpiration—aided by cohesion and adhesion Giant RedwoodsPlant Transpiration—aided by cohesion and adhesion
11 Water’s hydrogen bonds moderate temperature Water has high specific heatSpecific heat = heat needed to raise temp. of 1g of substance by 1ºCBoiling Point High .... water stays liquid longerAs such, water can act as heat reservoire, moderating Earth’s global temperature
12 Water’s hydrogen bonds moderate temperature It takes a lot of energy to disrupt hydrogen bondsable to absorb a great deal of heat energy without a large increase in temperatureAs water cools, a slight drop in temperature releases a large amount of heat
22 Properties of WaterA molecule in which the charges are unevenly distributed is called apolar molecule.cohesive molecule.hydrogen molecule.covalent molecule.
23 Properties of Water Hydrogen bonds between water molecules result from 2Hydrogen bonds between water molecules result fromadhesion between water molecules.magnetic attractions between water molecules.uneven electron distribution in each water molecule.ionic bonds in the water molecule.
26 Solutions and Suspensions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined.Strawberries and Sugar
27 Solutions and Suspensions Two types of mixtures can be made with waterSolutionsSuspensions
28 Solutions and Suspensions Two types of mixtures can be made with waterSolutionsAll the components of a solution are evenly distributed throughout the solution.In a salt–water solution, table salt is the solute—the substance that is dissolved.Water is the solvent—the substance in which the solute dissolves
29 Solutions and Suspensions When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules.Ions break away from the crystal and are surrounded by water molecules.The ions gradually become dispersed in the water, forming a solution.When an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions.
30 Solutions and Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out.The movement of water molecules keeps the small particles suspended.Suspension of flour in water
31 Some Important Biological Fluids Are Both Solutions and Suspensions Blood is mostly water, which contains many dissolved compounds.Blood also contains cells and other undissolved particles that remain in suspension as the blood moves through the body.
32 Acids, Bases, and pH Acids, Bases, and pH H20 H+ + OH- A water molecule can react to form hydrogen and hydroxide ions.H20 H+ + OH-Water is neutral because the number of positive hydrogen ions (H+) produced is equal to the number of negative hydroxide ions (OH-) produced.
33 Acids, Bases, and pH The pH scale Measurement system to indicate the concentration of H+ ions in solution.The pH scale ranges from 0 to 14.SolutionpH rangeH+/OH- ratioAcidconcentration of H+ ions greater than OH- ionsNeutral7.0concentration of H+ ions and OH- ions is equal.Baseconcentration of H+ ions less than OH- ions
37 pH Indicators Cabbage Juice Boiled cabbage creates a bluish/purplish juice that can be used to test pH of substances
38 pH Indicators Cabbage juice responds like litmus paper Indicator turns:Red in AcidsBlue in Bases
39 pH Indicators pH paper phenolphthalein -turns pink in presence of base
40 Acids, Bases, and pH Buffers The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5.If the pH is lower or higher, it will affect the chemical reactions that take place within the cells.enzymes denature & reactions stop (That’s a bad thing!)
41 Acids, Bases, and pHControlling pH is important for maintaining homeostasis.Buffers are weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.They accept H+ ions when they are in excess and donate H+ ions when they are depleted
45 Acids, Bases, and pH A dissolved substance is called a solvent. 1A dissolved substance is called asolvent.solution.solute.suspension.
46 Acids, Bases, and pH2A compound that removes ions from a solution is called a(an)base.buffer.acid.salt.
47 Acids, Bases, and pH3On a pH scale, a value of 2 means that the solution hasequal concentrations of H+ and OH- ions.the same concentration of H+ ions as pure water.higher concentration of H+ than in pure water.lower concentration of H+ than in pure water.
48 Acids, Bases, and pH4Tomato juice has a pH of 4, while soap has a pH of 10. How much more acidic is the juice?6 times more acidic1,000,000 times more acidic60 times more acidic1,000 times more acidic