Properties Of Water Essay, Research Paper

Properties of Water

Water is essential for life as we know it on earth. It is used by plants

and animals for basic biological processes which would be impossible without the

use of water. The origin of all life can be traced back to the water in the

Earth’s precambrien seas. Water is also the universal solvent. It reacts with

more 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 of

oxygen. It is attracted to itself by hydrogen bonds. Hydrogen bonds are weaker

than covalent bonds, but collectively these bonds hold water together and give

it its cohesiveness. These bonds are also very important to water’s ability to

absorb heat, as without hydrogen bonds water would have a boiling point of -80

degrees C and a freezing point of -100 degrees C.

In reality, however, water has a boiling point of 100 degrees C and a

freezing point of 0 degrees C. The amount of energy needed to raise the

temperature of one gram of water by one Celsius degree is called a Calorie. One

Calorie is about twice as much energy as you need to warm one gram of most other

fluids by the same amount. This makes water much better for regulating the

temperatures of animals and the environment.

Water also has a very high heat of vaporization. Converting one gram of

cold water into ice requires 80 Calories of energy. Converting the same amount

of very hot water into steam requires 540. The high amounts of energy required

to change water from its liquid state make water tend to stay a fluid. The

process of freezing water involves slowing down the activity of the water

molecules until they contract and enter into a solid state. Once the ice is

cooled down to 4 degrees or less, the hydrogen bonds no longer contract, but

they become rigid and open, and the ice becomes less dense. Because the ice has

become 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 it

takes a very long time to cool off enough that it freezes. This also traps just

enough warmth to keep marine animals alive during the winter.

The process of turning water into steam is a different story. Because it

requires the breaking of water’s hydrogen bonds, this process takes far more

energy than it does to turn water into ice. The extra energy that is used in

converting water into steam helps keep the overall temperature from getting too

hot. In this manner water regulates the temperature of both animals when they

sweat, and the earth through evaporation.

Water affects the earth’s ecosystems in very important ways as well. When

water in the earth’s saltwater bodies evaporates into the air. This water vapor

then cools off, becomes liquid again, and then falls as rain or snow. The salt

is left behind, and the resulting precipitation helps replenish the water in

lakes, streams, rivers, and the groundwater supply. However, all of this water

eventually 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 the

process of evaporation. These remain in the water and cause problems until they

are either filtered out by natural or artificial processes, or until they are

diluted 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 safe

for consumption.

The properties of water give it the ability to react with different

elements and molecules in very interesting ways. Water’s properties allow it to

be the focal point of many cellular functions, primarily because of its reactive

abilities.

Ionization is one example of these reactions. This occurs when a water

molecule in a hydrogen bond with another one loses an atom of hydrogen. The

remaining particle is a hydroxl ion. Micromolecules with different charges than

water can cause ionization to happen as well. During the process of ionization

water realeases an eaqual number of hydrogen (H+) and hydroxyl (OH-). This

dissociation process involves only a few water molecules at once. The actual

number is about 10-7 moles/liter).

Acids [L. acidus, sour] are molecules that release the hydrogen ions in

the dissociation process. Strong acids, such as hydrochloric, dissociate almost

entirely in water. Bases are molecules that take up these extra hydrogen ions.

Water passes through pores easily. Cells take advantage of this by

having ?channels? — tiny holes in the cell membrane. These are exactly the

right size that water can get through them, while larger particles are held

inside.

Osmosis [Gk. Osmo, pushing] is defined by the Sylvia Mader textbook as ?

the diffusion of water across a differentially permeable membrane?. This

process is caused by a fluid attempting to seek equilibrium by going from a high

pressure situation into a lower pressure one. This pressure that causes this

operation is known as osmotic pressure.

Another interesting state that water can be in is that of an isotonic

solution. These are solutions which neither water is neither gained nor lost,

and the pressure is equal on both sides of the cell membrane. When this

pressure is not equal, the degree of the inequality is defined as tonicity.

When the pressure is very unequal, so that the pressure causes water to

flow inward, it is known as a hypotonic solution [hypo, less than]. The ?less

than? prefix refers to a solution with a lower percentage of solute, and which

contains more water than the cell. The cell then swells, possibly even to the

point 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, more

than]. The ??more than? prefix in this word refers to a solution with a higher

level 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 grapefruit

in the sun.

Animals regulate the amount of water in their bodies in very individual

ways, each suited for the environment in which they each live. Sharks and fish

are able to live in an environment nearly saturated by salt by having a sort a

immunity to it. Some sharks survive by making their blood as toxic as the

surrounding water.

Certain seaside animals as well have developed ways to keep the salt in

their water from dehydrating them. Some kinds of birds and reptiles have a sort

of nasal salt gland which allows them to excrete the large amounts of salt that

they take in when they drink. Some mammals as well can live in highly saline

environments by making their urine stronger, and having very dry fecal material.

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