Water; Some Properties

The human body is about 90% water. We need it for circulation (our heart does more work when we do not drink sufficient water), it helps regulate body temperature, it is used in digestion, and in every cell activity takes place in a watery environment.

Water is an unusual liquid in that as it cools down towards 4 degrees Celsius it contracts, but on cooling further below 4 degrees it expands. As it forms ice it expands even more.

At sea level water boils at about 100 degrees Celsius. Higher up where atmospheric pressure is lower water boils at a lower temperature and food may not cook well. Pressure cookers can be used in this case to make the water boil at a higher temperature.

Water is also a very good solvent, which allows it to have dissolved waste materials from our bodies in. The urine, consisting mainly of dissolved waste materials, can therefore transport waste material out of our bodies.

Rain water contains gases dissolved in it and also particles of dust. Without dissolved gases water tastes flat and such water may be poured back and forth from one container into another to allow gas to dissolve. Aeration, which involves dissolving of oxygen, can kill microorganisms making it safer to drink. Other methods of purifying water involve boiling, filtering and distilling. Distilling involves turning water into steam and then back to water by means of condensation. Generally, boiling water for at least 15 minutes makes it safe to drink (but not if there are poisons in it).

Sometimes with soap, water forms a scum and there is no lather. We then say that there is hardness in the water. This is mainly due to calcium and magnesium compounds dissolved in the water. There are various methods of softening water and one way is to add washing soda.

With our growing population using more water we need to take care that we do not waste this essential chemical.

Reference: Chemistry for the health sciences by Sackheim and Schultz