We often relate two things or persons in life that won’t go hand in hand, won’t belong in the same group, or are very different from each other to oil and water. Now, why did we associate these two kinds of liquid to being uncooperative with each other? If we pour a little bit of vegetable oil in water and shake it very well, it might seem that both of the liquids have mixed. But slowly, small droplets of oil form at the surface of the water, and they will continue to form these droplets until they combine to make larger drops. Eventually, the oil settles on the top of the water as a different layer in the container. People know that these two liquids don’t really mix, but hardly a few actually seem to know the scientific principle behind this phenomenon.
Water and oil are made up of very different elements and have their own distinct physical and chemical characteristics. The water molecule, which is often called H2O, is composed of two hydrogen atoms and one oxygen atom. But these atoms are often not arranged in a straight line. The two hydrogen atoms are aligned to only one side of the oxygen atom, which is the one that occupies a sharp end in the structure, thus forming the shape of the letter V. The water molecule has a small positive charge at the end of the hydrogen atoms, while the end of the oxygen atom has a slightly negative charge. This difference in charges is due to the varying frequency of electronegativity of the two atoms. The electronegativity then makes water a polar molecule. As most of you know, opposite charges attract each other. As such, the negative poles found on each water molecule are attracted to the positive poles carried by other water molecules. This connection constitutes a tight bonding between the water molecules, which is called hydrogen bonds.
As for oil, this liquid is considered a non-polar chemical. Oils are usually made of fatty acids. The electron sharing that is occurring on its molecules is less prominent compared to water because it consists of non-polar molecules that basically have no charge. Because there are no charges happening in the oil molecules, they are not attracted to other polar molecules, as opposed to the water that is comprised of molecules that attract each other fairly easily and quickly. However, they still do attract molecules of their own kind and cluster together, although it is not a tight bond. Polar molecules would dissolve only in polar solvents, while non-polar molecules dissolve only in non-polar solvents. The nature of these poles essentially separates water and oil into two separate layers since they have different charges and composition. The oil would typically float on top of the water because it is less dense than water, and the lesser density may be caused by the less tight connection between the oil molecules.
However, thanks to the advancement of science brought by technology, it is actually possible now to mix the two substances. However, the bond is done using a mediating agent, and this agent is called the emulsifier. Most of these emulsifiers create bonds with both oil and water molecules. The end product is an emulsion wherein one substance is spread through the other. Laundry and cleaning products like detergents and soaps that we use in our daily lives are great examples of emulsifiers.
What is the densest liquid on Earth?
While water is quite a dense liquid, it is not considered the densest on the planet, as that distinction belongs to a peculiar liquid called mercury. Now, there are many people who would say that mercury is supposed to be a liquid because it has a distinct form, and its color is not transparent or translucent; however, these descriptions are actually wrong.
Mercury does not have a distinct form since it is able to changes its shape based on what container is used to store it, which is a feature found in all liquids like water and oil. Also, a liquid will still be a liquid even if it isn’t transparent, but for mercury’s case, its solid and opaque color is caused by its composition. Mercury is not just any kind of liquid, as it is a liquid metal, a type that is made up of alloys that melt a very low temperature. The melting of these alloys causes its structure to have a liquid form. Mercury rarely has a solidified form, since it melts at room temperature, which is supposed to be the temperature found almost anywhere on Earth. However, it can become solid at freezing temperatures, much like ice, but it only freezes at negative 38.83 degrees Celsius, while water turns to ice at 0 degrees.
Because of its alloy composition, its molecules tend to bond even more tightly than water, hence the reason why it is the densest liquid on Earth. If you put oil, water, and mercury with the same volume in a glass, you would immediately notice that mercury would go at the bottom, water would be at the middle, and oil would be at the top. There is currently no way for scientists to mix water and mercury together, unlike what we did for water and oil. Because they don’t really mix, you can treat the mercury in the glass as a piece of rock that just moves like jelly at the bottom.