It is quite easy for you to describe those things you see or hear. Yet generally, we have considerable difficulty in putting any name to a smell. We try to describe it by comparing it to some other smell; and tend to describe the feelings those aromas awaken in us. We refer to those smells we like as "nice" or pleasant, and to those we do not as "bad" or unpleasant, because a great many smells we encounter in our daily lives do not have actual names.
What we refer to as a smell is actually a reaction to chemical particles—in other words, molecules—given off by an object. The origin of the smell of freshly ground coffee that you find so delightful is actually the floating airborne molecules emanating from it. The more of these are given off, the stronger the aroma. The reason why a baking cake smells so much more strongly than a stale one is because the cake in the oven is emitting so many more scent particles. Scent molecules begin moving in the air more freely under the effect of heat, and are able to disperse over a wide area. But be aware that delicate balances have been specially arranged for human life. There are materials such as stone, iron and glass around you that you cannot smell, because these substances do not vaporize at room temperature. But assume for a moment that everything in your room suddenly began giving off aromas: Can you imagine how disturbing and even life-changing that would be?
Another interesting fact is that although water vaporizes at room temperature and even below, it has no odor. This special feature in water is most important, since it means that there is no difference between the scent of a dried rose and one that has been freshly watered and still has droplets on its petals. In other words, the rose's natural perfume is unimpaired. Furthermore, the water vapor, or moisture, in the air actually strengthens the effect of any existing smell. For instance, water molecules that vaporize after a downpour of rain raise scent particles up into the air and assist in spreading the scent of flowers all around.
No one knows how many varieties of odors there are in nature. Bearing in mind the existence of millions of molecules, we may safely say that the variety of scents is enormous. Studies have been carried out to place these aromas into various categories. But due to the extraordinary variety of smells, no satisfactory classification has ever been achieved.
The microscopic variation between molecules gives any one smell its particular characteristics. (Figure 1) For example, the feature that differentiates a cooked, fresh egg from a rotten one lies in the structures of the particles the two eggs give off. Differences in the chemical structures between various molecules are based, in turn, on very delicate variations. Indeed, the addition or subtraction of a single carbon atom can turn an attractive smell into a repellent one!
The design in every point in the universe can immediately be seen in the structures of scent molecules. The unique aromas of cocoa, lavender or strawberry are the results of the molecules that give rise to these smells, and to the specially arranged bonds among them. Every molecule has been planned in light of a specific purpose, in the exactly the form it needs to be. There is no doubt that this magnificent design belongs to God, Who created everything and determined it most exactly. (Surat al-Furqan: 2)
The three derivative scents of the chemical substance whose structure is shown in (91) resemble that of the rose. Yet each is distinguished from the other two by a different smell. The scents of lilac and spices (92), ozone and fruit (93) and cinnamon, carnation, spices and lilac all smell like the rose mixed with these scents.
Very small differences between molecules cause flowers and fruits to have very different scents from one another.