Properties of WaterWater is essential for life as we know it on earth. It is used by plantsand animals for basic biological processes which would be impossible without theuse of water. The origin of all life can be traced back to the water in theEarth’s precambrien seas.
Water is also the universal solvent. It reacts withmore elements and compounds than any other substance known to man. Water is a polar molecule made up of on atom of hydrogen and two atoms ofoxygen. It is attracted to itself by hydrogen bonds. Hydrogen bonds are weakerthan covalent bonds, but collectively these bonds hold water together and giveit its cohesiveness. These bonds are also very important to water’s ability toabsorb heat, as without hydrogen bonds water would have a boiling point of -80degrees C and a freezing point of -100 degrees C.
In reality, however, water has a boiling point of 100 degrees C and afreezing point of 0 degrees C. The amount of energy needed to raise thetemperature of one gram of water by one Celsius degree is called a Calorie. OneCalorie is about twice as much energy as you need to warm one gram of most otherfluids by the same amount. This makes water much better for regulating thetemperatures of animals and the environment.
Water also has a very high heat of vaporization. Converting one gram ofcold water into ice requires 80 Calories of energy. Converting the same amountof very hot water into steam requires 540. The high amounts of energy requiredto change water from its liquid state make water tend to stay a fluid.
Theprocess of freezing water involves slowing down the activity of the watermolecules until they contract and enter into a solid state. Once the ice iscooled down to 4 degrees or less, the hydrogen bonds no longer contract, butthey become rigid and open, and the ice becomes less dense. Because the ice hasbecome less dense, it floats on liquid water. Water freezes from the top down.
Once the top freezes, it acts as an insulator, so that the water beneath ittakes a very long time to cool off enough that it freezes. This also traps justenough warmth to keep marine animals alive during the winter. The process of turning water into steam is a different story. Because itrequires the breaking of water’s hydrogen bonds, this process takes far moreenergy than it does to turn water into ice. The extra energy that is used inconverting water into steam helps keep the overall temperature from getting toohot.
In this manner water regulates the temperature of both animals when theysweat, and the earth through evaporation. Water affects the earth’s ecosystems in very important ways as well. Whenwater in the earth’s saltwater bodies evaporates into the air. This water vaporthen cools off, becomes liquid again, and then falls as rain or snow.
The saltis left behind, and the resulting precipitation helps replenish the water inlakes, streams, rivers, and the groundwater supply. However, all of this watereventually flows down to the level of the oceans, and the cycle begins again. Because of this cyclical pattern, water is consided to be a renewable resource. However, some chemical impurities can remain with the water, even through theprocess of evaporation. These remain in the water and cause problems until theyare either filtered out by natural or artificial processes, or until they arediluted enough that they are no longer a problem.
Of all the water on the earth,only three percent is fresh. Of that three percent, only 1/3 is considered safefor consumption. The properties of water give it the ability to react with differentelements and molecules in very interesting ways. Water’s properties allow it tobe the focal point of many cellular functions, primarily because of its reactiveabilities.
Ionization is one example of these reactions. This occurs when a watermolecule in a hydrogen bond with another one loses an atom of hydrogen. Theremaining particle is a hydroxl ion. Micromolecules with different charges thanwater can cause ionization to happen as well. During the process of ionizationwater realeases an eaqual number of hydrogen (H+) and hydroxyl (OH-).
Thisdissociation process involves only a few water molecules at once. The actualnumber is about 10-7 moles/liter). Acids L. acidus, sour are molecules that release the hydrogen ions inthe dissociation process.
Strong acids, such as hydrochloric, dissociate almostentirely in water. Bases are molecules that take up these extra hydrogen ions. Water passes through pores easily. Cells take advantage of this byhaving channels — tiny holes in the cell membrane.
These are exactly theright size that water can get through them, while larger particles are heldinside. Osmosis Gk. Osmo, pushing is defined by the Sylvia Mader textbook as the diffusion of water across a differentially permeable membrane. Thisprocess is caused by a fluid attempting to seek equilibrium by going from a highpressure situation into a lower pressure one. This pressure that causes thisoperation is known as osmotic pressure. Another interesting state that water can be in is that of an isotonicsolution.
These are solutions which neither water is neither gained nor lost,and the pressure is equal on both sides of the cell membrane. When thispressure is not equal, the degree of the inequality is defined as tonicity. When the pressure is very unequal, so that the pressure causes water toflow inward, it is known as a hypotonic solution hypo, less than. The lessthan prefix refers to a solution with a lower percentage of solute, and whichcontains more water than the cell. The cell then swells, possibly even to thepoint where the cell will burst.
These exploded cells are referred to as lysis. The pressure that caused them to pop in the first place is referred to turgor L. turg, swell pressure. The opposite state is referred to as a hypertonic solution hyper, morethan.
The more than prefix in this word refers to a solution with a higherlevel of solute, and the cell contains more water than the outside solution. Therefore, a cell in a hypertonic solution tends to shrivel up like a grapefruitin the sun. Animals regulate the amount of water in their bodies in very individualways, each suited for the environment in which they each live. Sharks and fishare able to live in an environment nearly saturated by salt by having a sort aimmunity to it. Some sharks survive by making their blood as toxic as thesurrounding water. Certain seaside animals as well have developed ways to keep the salt intheir water from dehydrating them.
Some kinds of birds and reptiles have a sortof nasal salt gland which allows them to excrete the large amounts of salt thatthey take in when they drink. Some mammals as well can live in highly salineenvironments by making their urine stronger, and having very dry fecal material. .
