Physical and chemical characteristics of waterPosted: March 14, 2011
Physical and chemical characteristics of water
Water is a substance, not an element. This became clear only in the late 18th century, when Lavoisier has specifed its exact composition – two hydrogen atoms plus one oxygen atom bound in a compound by covalent bond.
H2O is the chemical formula with which we word the water. Positively charged hydrogen atoms are situated on either side of the negatively charged oxygen atom. Thus, the molecules that are produced are oppositely charged and draw each other. We call the water adhesive and cohesive, and it is because of these two properties – surface tension and the ability to draw other substances. For example, the droplets are formed due to the attraction of water molecules and if there was no gravity, they would be completely round.
Water has a neutral pH of about 7. It is neither alkaline nor acidic. Water, wherever it goes, it draws and carries with it any chemicals, no matter harmful or helpful. With its ability to dissolve them, there is no other substance can match it.
Water is a unique substance with unique physical properties. It is in constant motion, enter into relations with other substances and change them. This substance is odorless and tasteless at normal temperature and pressure. It is the only substance which could be in all the three aggregate states: liquid, solid and gaseous. The liquid water has no color and because of that living organisms – plants and animals – survive underwater.
Water changes from one into another physical state and never disappears. It boils at 90°C and freezes at 0°C. In freezing water expands. An interesting phenomenon is that the solid state of water – ice – is less dense than the liquid state, so actually ices swim on the water without sinking.
Water has a high heat index, so it is especially important for the climate and changing of seasons, and in industry, where it is used as a cooler or a heater. It is not a conductor, but if ions are dissolved in it, it becomes conductive. Measuring its electrical conductivity, we can see the purity of water.
Water quantity on Earth is generally constant, i.e. it is unchangeable. In various parts of the atmosphere and hydrosphere there is constant transition of water. However, the concentration of water in them is different. The mentioned transition is called water cycle, which is periodically repeated. It includes several basic processes: evaporation from water bodies, water vapor concentration and cooling in the clouds; rains; rain draining into the ocean. We see that this is a logical and closed cycle, without which we would not have been alive.
Water properties – physical and chemical – are out of reach for any other substance on the planet. It gives us life; it purifies and maintains our vital function. It is extremely necessary and indispensable to the living nature. Some organisms are composed of more than 90% of water; the human body contains over 60% water, our lungs – about 90%. This comes to remind us just one thing, namely that the best for living matter is only one thing – Water.