Quiz 2: Water

Biology

(a)The water molecules in the gaseous state show the same properties as that of other gases. This is because under standard temperature and pressure set up by IUPAC (International Union of Pure and Applied Chemists), all the gases tends to have same number of molecules. It was observed by the IUPAC scientists that when gases are subjected to similar physical conditions of temperature and pressure, they tend to arrange freely with negligible force of attraction. When gases attain such state, all of them were found to have same number of molecules in the given volume. Thus, gas-phase of water has same properties as that of other gases. (b)We have observed that any substance exists maximum only in two phases that can be; liquid and solid (like metals), liquid and gas (like acids) or solid and gas (like camphor). There is only one substance that is water which is versatile in its nature as it can exist in all the three forms. The water is found in the form of gaseous state as vapours, in liquid state as liquid water and in solid state as ice. This is possible due to the structure of water molecule. The two atoms of hydrogen and one of oxygen arrange themselves in such a way in three dimensions that it can be found in all the three states of matter. Thus, the unusual phase transitions of water are solid, liquid and gas. In the solid state water molecules are at very low temperature that tends to compress them close to each other forming ice cube. In liquid state, the water molecules are under standard temperature and pressure and are free to move but attached to each other by hydrogen bonds. In the gas phase, the water molecules are under high temperature that allows them to absorb energy and get free form forces of attraction and move freely. (c) We have already discussed above the unusual phase transitions of water. The reason for this unusual behavior is the physical conditions and the three dimensional structure of individual molecule. In the solid state water molecules are at very low temperature that tends to compress them close to each other forming ice cube. In liquid state, the water molecules are under standard temperature and pressure and are free to move but attached to each other by hydrogen bonds. In the gas phase, the water molecules are under high temperature that allows them to absorb energy and get free form forces of attraction and move freely.

The water molecule consists of two hydrogen atom and one oxygen atom arranged as follows: img In pure water, the water molecules tend to remain in equilibrium between its stable and protonated state. This can be understood as follows: img Thus, it can be said that one water molecule at present carries proton and exists as hydronium ion or in the protonated (H ₃ O + ) state while others would be in the stable (H ₂ O) state. This proton is transported from one molecule of water to another at a very high rate as compared to diffusion. Thus, it can be said that above 90 % of water concentration can be found as water (H ₂ O).

Electronegativity means the capacity of the atom to attract electrons and enter them into their valence shells. This property depends upon the size of atom. If the atom's size is small them its valence (outermost) shell will be close to the nucleus and thus, nucleus can easily pull the incoming electron/s. This property is carried out by atoms to attain stable electronic configuration. If the atoms fall short of two electrons they will gain from other atoms which have two extra electrons. In this way, if some atom is there to collect electron/s then there must be the one who can donate. Thus, the concept of electronegativity applies only to bonds as there are two atoms always. It is not possible that there is an atom who can release electrons but there is no one to take it up or vice-versa. Thus, an atom alone is not capable of taking up electrons instead there should also be the one to donate. So, it applies only to bonds.