Special Nature of Water - (SCI-15)

Introduction

Do you know that we have a use for water in all of its three forms. We drink water in liquid form, we put ice or water as a solid into our drinks, and we inhale gaseous water as part of the air we breathe.

There are very few substances on the surface of the Earth that can be found naturally in these three states or forms, that is as liquid, solid and gas. Water is one of these remarkable substances. This is one of water’s most unique properties.

Another very unique property of water is that, when it is a solid it floats on its liquid. This is a very rare thing, usually the solid of any substance when placed in a container of the same substance in the liquid state will sink to the bottom of the container. This is because the solid of nearly all substances is denser than the liquid, but so for water.

Obviously water has something special going on its chemical nature and this is what this and the next few posts are about.

Ice Floats on Water

The following excerpt has been taken from the book “The Water Planet”, published by the National Geographic Education Division, D.C.

“Effects of Bonding The polarity of water molecules makes water great for dissolving other substances, such as sea salts and substances that travel through your body. Polarity also means that ice will float on liquid water. As water freezes, the weak bonds between the molecules form an open arrangement of molecules, as seen in Figure 7.

The molecules, therefore, are farther apart when they are frozen than they were as liquid. This causes ice to have a lower density than liquid water, letting it float on water. In large bodies of water, floating ice prevents the water below from freezing. If lakes froze from the bottom up, they would freeze solid every winter, killing all living things inside.”

Conclusion

The reason why ice or solid water floats on liquid water is due to the way water molecules bond when they are a solid. They bond in such a way that the molecules spread out making the solid (ice) less denser. Notice that when you freeze water it expands, if it were to contract it would certainly not float on liquid water.

The diagram shows this quite clearly.

This marvellous polarity property of water allows life to continue in winter. If the water molecules did not have this property then lakes and rivers would freeze all solid.

The more we look at water, we really come to realise that it is just perfect to support and maintain life the way we have it right now. If we were to change water we would change life the way we now it now.

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