The Properties of Water Water is arguably the most important biochemical, in one way or another it is intricately involved in just about every process on this planet. It has many properties but only the following will be covered at the moment. Some of the obvious properties is that it’s a colourless, tasteless and transparent liquid but some of the chemical properties are listed below. Water is a polar molecule. Water's unique properties are largely a result of its simple composition and structure. Water is composed of two hydrogen atoms and one oxygen atom. As shown in the diagram, the two hydrogen atoms are smaller and they rest on both sides of the larger oxygen atom. When the hydrogen atoms combine with oxygen, they each share their single electron and form what is known as a covalent bond. Because electrons are more attracted to the positively charged oxygen atom, the hydrogen’s become slightly positively charged and the oxygen atom becomes negatively charged. This separation between negative and positive charges creates what is known as a polar molecule, meaning a molecule that has an electrical charge. Although the water molecule as
a whole has no charge, the parts of it, the hydrogen wings and the oxygen body, do exhibit individual charges.Water acts as a solvent. More substances dissolve in water than in any other liquid, for this reason it is often called the "Universal Solvent." The reason for water's excellent ability at dissolving relates to its polarity; water offers positive and negative charges to which other atoms of molecules can attach. Note how water molecules can surround a positive sodium ion or a negative chloride ion, the common components of table salt. Water surrounds positive atoms (or the positive end of ...
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a whole has no charge, the parts of it, the hydrogen wings and the oxygen body, do exhibit individual charges.Water acts as a solvent. More substances dissolve in water than in any other liquid, for this reason it is often called the "Universal Solvent." The reason for water's excellent ability at dissolving relates to its polarity; water offers positive and negative charges to which other atoms of molecules can attach. Note how water molecules can surround a positive sodium ion or a negative chloride ion, the common components of table salt. Water surrounds positive atoms (or the positive end of a polar molecule) with the negative charge of the oxygen atom. Around negatively charged atoms or molecules, water places the positive hydrogen atoms first.Water exists in three forms. Water can exist on our planet in three physical states. Water can be a liquid (water), a gas vapour (clouds), or a solid (ice). Think about this. As most of you know, water turns into a vapour (i.e. boils) at 100°C and turns into ice (i.e. freezes) at 0°C at standard atmospheric pressure (i.e. at sea level). However, these changes of state require energy input or removal in addition to the energy input/removal required to change the temperature.Water has a neutral pH. pH is a measure of the acidity or alkalinity of a substance. The acidity of alkalinity of a substance depends on the concentration of hydrogen ions (acidic) or hydroxide ions (alkaline). The pH scale ranges from 0 to 14. The lower the pH the greater the acidity and the higher the pH, the more alkaline a substance. Pure water has a pH of 7, which is neutral. Seawater with its dissolved minerals tends to be slightly basis, around 8 or so. Water has a high latent heat of fusion. To increase the temperature of water, energy in the form of heat must be added. This heat-energy is measured in calories. One calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree. Thus, to raise the temperature of 1 gram of water from 0 degrees to 100 degrees would require 100 calories of heat. However, to change 1 gram of water from a liquid to a gas requires 540 calories. No change in temperature occurs; there is only a change in the physical state of the water as it turns from a liquid to a gas. The heat needed to change water from a liquid to a gas is called the latent heat of vaporisation. Water's exceptionally high latent heat of vaporization is what makes water so hard to boil. As we all know, vaporisation of water occurs at other temperatures as well. This process has to do with random motion of molecules at liquid-gas interfaces and physical laws governing vapour pressure. Simply put, not all water molecules in a glass of water have the same energy. Those that have lots of energy leave first, i.e. they vaporize. As they leave, they take their heat energy with them. That is why the surface of water cools first and why you feel cool when water evaporates from your body either through sweating or by getting wet. However water turns into vapour, the rules of the latent heat of vaporization still apply. On average, 540 calories of heat are required to evaporate 1 gram of water, although this number changes slightly as temperature changes.Water has a high heat capacity. Water has the highest heat capacity of any liquid or solid, except ammonia. The heat capacity of a substance is defined as the amount of heat that is required to raise the temperature of 1 gram of a substance by 1 degree. As we learned above, this amount of heat for water is defined as 1 calorie. This means that the heat capacity of all other substances is lower, i.e. that it takes less than 1 calorie to raise the temperature of 1 gram of the substance by 1 degree. The main point here is that water can absorb a tremendous amount of heat. For this reason, the oceans of the world tend to vary in temperature much less than land. The average range of temperatures in the ocean is from -2 degrees to 35 degrees C. On land, temperatures may vary anywhere from -70 degrees to 57 degrees C. Compare also the moon, which has no water. Temperatures here range from -155 degrees to 135 degrees C. Thus, water acts like a heat buffer for the globe. Its ability to absorb heat at one location and transport it to another locations is extremely important in moderating the climate of our globe. On a smaller scale, anyone who has lived near the beach has probably noticed that days are not as hot during summer and nights are not as cold during winter. This is because of the high heat capacity of water and its ability to absorb to release tremendous amounts of heat without changing temperature.Water has a high surface tension. The ability of water molecules to quickly break and re-form hydrogen bonds gives it a property called cohesion. Water's high amount of cohesion makes it such that a kind of "water barrier" is set up that allows things to float easier on the surface and causes water to form beads. An example of this is some insects can skate across the surface of the water. They can do this because water has a high surface tension. Water is essential to all living organisms. Water is major component of cells forming between 70 and 95% of the mass; human beings are about 60% water. Water also provides an environment for all the organisms that lie in the water; three quarters of the planets surface is covered in water.