Packet #7 Various Chapters Water Packet #7 Various Chapters Tuesday, November 20, 2018

Introduction Most abundant liquid in the world Makes up at least half of all living organisms and up to 95% of some species. 75% of earth is submerged in water Tuesday, November 20, 2018

Forms of Water Molecules 11/20/2018

Forms of Water Molecules H2O Naturally occurring water consists of 99.76% H2O The remainder consists of various isotopes HDO & D2O Formed with an isotope of hydrogen called deuterium 2H Deuterium is most often found with a normal hydrogen atom but occasionally, D2O is formed Both are called heavy water and have deleterious effect on living organisms. 18O Tuesday, November 20, 2018

Water as a Polar Molecule 11/20/2018

The Water Molecule H2O is a polar molecule and results in the ability for the molecule to form hydrogen bonds In most cases, with other water molecules to form liquid, solid or gaseous water. Due to the opposite charges Tuesday, November 20, 2018

Solubility Water, versatile solvent due to its polarity, is used to form an aqueous solution. A solution is considered as a homogeneous (of uniform structure or composition throughout ) mixture of two or more substances, which may be solids, liquids, gases, or a combination of these. Examples of Aqueous Solutions Water (Solvent) and salt (Solute) Water (Solvent) and sugar (Solute) Tuesday, November 20, 2018

Solubility II “Likes dissolves likes” Oil and water are dislikes Polar with polar Non-polar with non-polar Oil and water are dislikes Water = polar Oil = non-polar We say that oil and water are nearly completely immiscible The oil is suspended Tuesday, November 20, 2018

Water & Ionic Compounds The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them Tuesday, November 20, 2018

Water & Proteins Water can also interact with polar molecules such as proteins This oxygen is attracted to a slight positive charge on the lysozyme molecule. This oxygen is attracted to a slight negative charge on the lysozyme molecule. (a) Lysozyme molecule in a nonaqueous environment (b) Lysozyme molecule (purple) in an aqueous environment such as tears or saliva (c) Ionic and polar regions on the protein’s Surface attract water molecules. + – Figure 3.7 Tuesday, November 20, 2018

Water & Biochemical Reactions Most biochemical reactions, that occur within cells of the body, occur in water Since most biochemical reactions occur in water, it is important to calculate the concentration of solutes in an aqueous solution Molarity The number of moles of a solute per liter of solution Molality The number of moles of a solute per 1000 g of solvent Mole The number of molecules of a substance in a given mass Tuesday, November 20, 2018

Hydrophilic vs. Hydrophobic Hydrophilic substance Water loving Has an affinity for water Hydrophobic substance Water hating Does not have an affinity for water Tuesday, November 20, 2018

Water Molecules & Hydrogen Bonds 11/20/2018

The Water Molecule & Hydrogen Bonds Liquid, solid and gaseous water is formed as hydrogen bonds are formed, and broken, between the oxygen, and hydrogen, atoms of individual water molecules. Tuesday, November 20, 2018

Phases of Matter {Water} Tuesday, November 20, 2018

Importance of Hydrogen Bonds in Liquid Water 11/20/2018

Cohesion Cohesion Tendency of molecules, if in substance, to hold together by mutual attraction The hydrogen bonding of individual water molecules result in strong cohesion forces. Tuesday, November 20, 2018

Cohesion & Surface Tension What does this (strong cohesion forces) mean? One drop of liquid water will assume the smallest possible area on a surface The water molecule will form a sphere Water molecules, at the surface of the drop, will be drawn together forming a skin-like layer off molecules on the surface. The force formed when the individual water molecules draw together at the surface of the drop is called surface tension. Tuesday, November 20, 2018

Surface Tension Is a measure of how hard it is, the amount of force necessary, to break the surface of a liquid Insects walking on the surface of water and the movement of water up plants are two biological processes that can occur as a result of the cohesive properties of water molecules. Tuesday, November 20, 2018

Homework Assignment Conduct experiment determining how much water can a penny hold Must use an old and a new penny Difference in composition Must complete at least 20 trials for each penny Must complete a full lab report with a 3 page background research section on cohesion forces and surface tension PAPER MUST BE SUBMITTED to Mr. Barrow Due 2:45pm EDT September 2009 Tuesday, November 20, 2018

Adhesion & Capillarity Forces 11/20/2018

Adhesion Adhesion The attraction of molecules of different compounds to one another. The ability of water to cling readily to other molecules is responsible for the upward movement of water when a small-bore tube is dipped into it. This phenomenon is called capillary action. Tuesday, November 20, 2018

Capillary Action in Plants Xylem vessels, found in plants, are responsible for the movement of water in plants. Xylem vessels, of a diameter 0.02mm can, in theory, support a column of water of height 1.5m by capillary forces. Capillary action, resulting from cohesion, has one of its main biological effects being the upward movement of water from soil. Tuesday, November 20, 2018

Thermal Capacity Tuesday, November 20, 2018

Thermal Capacity Thermal capacity and specific heat go hand in hand. Hydrogen bonding results in the necessity of heat to cause increased molecular movement Formation of steam from liquid water for example. When heat energy is applied to liquid, solid or gaseous water, it is first used to break hydrogen bonds Tuesday, November 20, 2018

Thermal Capacity II The presence of hydrogen bonds makes liquid water resistant to temperature change This is why the temperature of liquid water rises only very slowly for a given amount of added heat Since water is resistant to temperature change, it is said to have a very high specific heat The amount of heat that must be absorbed or lost for 1 gram of that substance to change its temperature by 1˚C Tuesday, November 20, 2018

Thermal Capacity & Enzymatic Reactions Why is the use of heat energy for breaking hydrogen bonds important? Allows thermal stability so that enzymatic reactions(biochemical reactions) in water mediums are not subjected to large temperature fluctuations and can take place at a more constant rate. If there were no hydrogen bonds, water would be a gas at most temperatures Tuesday, November 20, 2018

The Cooling Effect As temperatures outside rise, the body begins to sweat. The sweat allows water to aid in cooling as air passes over it. With hydrogen bonds in place, at high temperatures, when humans sweat, it allows water to aid in cooling as the wind blows in areas of low humidity. Water, with a high heat of vaporization, is most effective in cooling the body. Heat of Vaporization The amount of heat required to convert a unit mass of a liquid at its boiling point into vapor without an increase in temperature. Water stays around long enough for the body to cool. Tuesday, November 20, 2018

Density Tuesday, November 20, 2018

Density Water has a maximum density at 4ºC This is when water is in a liquid state H2O (l) is more dense than H2O (s) Water freezes from top downward allowing ice to form at the top Ice at top can insulate the warmer water below that layer from colder temperatures above Prevents large bodies of water from freezing solid and allowing the survival of aquatic organisms Tuesday, November 20, 2018

Dissociation & pH Tuesday, November 20, 2018

Dissociation Water has a slight tendency to dissociate into ions according to the equation 2H2O  H2O+ + OH- H2O  H+ + OH- Hydronium ions and hydroxide ions Tuesday, November 20, 2018

Dissociation II Apart from dissociating itself, water readily causes the dissociation of other substances placed in it. Making it an excellent solvent. Tuesday, November 20, 2018

Neutral pH In 1 liter of water, this dissociation produces 1/10,000,000 (10-7) mole of hydrogen ions. Equivalent to a pH of 7 Neutral Tuesday, November 20, 2018

Acidic pH If the concentration of hydrogen ions is higher than what is seen at neutral pH, then the solution would be acidic An acid, therefore, is a substance that donates hydrogen ions Increases hydrogen ion concentration Example If the concentration of hydrogen ions is 1/1000 (10-3), then the pH would be 3 Tuesday, November 20, 2018

Basic pH If the concentration of hydrogen ions is lower than what is seen at neutral pH, the solution would be basic A base is a substance that is hydrogen ion acceptor Decreases hydrogen ion concentration Example If the concentration of hydrogen ions is 1/1,000,000,000 (10-9) the pH would be 9. Tuesday, November 20, 2018

Buffers A buffer solution is one that retains a constant pH despite the addition of small quantities of acids or bases. Buffers contain both hydrogen ion donors and acceptors. Hydrogen carbonate ions may act as an acceptor or a donor Hydrogen carbonate salts and phosphate salts are responsible for the buffering of blood. pH of 7.4 Tuesday, November 20, 2018

Effect of Sudden Changes in pH Changes in concentration of ions can have a great affect on living organisms Particularly enzymes Why? Answer to come in protein & enzyme packets. 11/20/2018

pH Scale 11/20/2018