Water Properties PDF

All living organisms require water more than any Water other substance Most cells are composed of 70-95% water Water is the molecule Most cells are surrounded by water that supports all of life First sign...

All living organisms require water more than any Water other substance Most cells are composed of 70-95% water Water is the molecule Most cells are surrounded by water that supports all of life First sign NASA looks for when identifying habitible mergent properties of water It is very cohesive Its density changes with temp Four of water’s properties that facilitate an environment for life are: Its ability to moderate temperature It is a very versatile solvent he bonds that hold water together   Hydrogen + bond Polar covalent bonds   +   +   + Cohesive ability Cohesion – an attraction between the same substances Adhesion – an attraction between different substances The many hydrogen bonds that hold water together are responsible for it’s strong cohesive ability Surface tension Evapotranspiration bility to moderate temperature Water absorbs heat from warmer air and can release stored heat to cooler a Cooling the air Warming the air Burbank San Bernardino Santa Barbara 73° 100° 90° Los Angeles Riverside 96° (Airport) 75° Santa Ana 84° Palm Springs 70s (°F) 106° 80s Pacific Ocean 68° 90s 100s San Diego 72° 40 miles bility to moderate temperature Kinetic energy – the energy of motion Heat – a measure Temperature – a of the total amount measure of the of kinetic energy intensity of heat due to due to molecular the average kinetic motion energy of molecules Celsius scale (oC) Fahrenheit scale (oF) Water freezes – 0oC Water freezes – 32oF Water boils – 100oC Water boils – 212oF o F = (9/5)oC + 32 Conversions: o C = (oF – 32)5/9 bility to moderate temperature pecific heat – the amount of energy it takes to raise 1 g of a substance by 1oC For water that is: 1 cal/g/oC “Calories” on a food label are actually A Calorie (cal) is the kilocalories amount of heat required (kcal) to raise the temperature of 1 g of water by 1oC bility to moderate temperature Water’s high specific heat can be traced to hydrogen bonding Heat is Heat is released absorbed when hydrogen when hydrogen bonds form bonds break The high specific heat of water minimizes temperature fluctuations to within limits that permit life! bility to moderate temperature This feature of water also contributes to evaporative cooling Heat from skin is absorbed during the breaking of the hydrogen bonds This helps stabilize temperatures in organisms as well as bodies of water xpansion upon freezing In liquid water the molecules move around and the hydrogen bonds break and re-form Ice has much less kinetic energy so the bonds don’t strain and Ice floats in liquid water because it takes on a break. They crystalline structure making it less dense than are very stable liquid water xpansion upon freezing Water is its most dense at 4oC (39oF) When it gets colder than 4oC, the density decreases This is also why we have fall and spring turnover in our lakes. How do you think that works? ersatility as a solvent Water acts as a very good solvent and can dissolve many different types of compounds necessary for life Solvent – dissolving agent of a solution Solution – a liquid Solute – that is a substance that is homogeneous dissolved in a mixture of a solution substance An aqueous solution is one in which water is the solvent ersatility as a solvent  Na Water’s polarity  is what makes it    a good solvent.   It can form  Na  hydrogen bonds  with ions or   other polar Cl Cl molecules         When a polar compound is dissolved in water, a hydration shell is formed from water molecules surrounding the charged regions of the molecules or ions ersatility as a solvent Even large molecules, like proteins, can dissolve in water if they have polar regions +    + e additional things to know about biological solutions 1. Chemical reactions depend on collisions of the solute, which are floating around in water randomly More solute More collisions Faster reaction and more product e additional things to know about biological solutions 2. Water is always in a state of dynamic equilibrium Hydronium Hydroxide 2 H2O ion (H3O+) ion (OH) +  Adding acids or bases modifies the concentrations of H+ and OH- acid base e additional things to know about biological solutions 3. Acids and Log scale Bases Base – any pH = -log [H+] substance that increases the OH- concentration of a solution Acid – any substance that increases the H+ concentration of a solution e additional things to know about biological solutions Buffers are substances that 4. Buffers minimize changes in The internal concentrations of H+ (H30+) and pH of most living cells OH- must remain close to ph 7 In human blood plasma we have a buffer system made of carbonic acid and bicarbonate H2CO3 + H2O H3O+ + HCO3- Carbonic acid bicarbonate H2CO3 + OH- In basic conditions: H2O + HCO3- neutralized HCO3- + H+ In acidic conditions: H2CO3