Water through the lens of Physics and Chemistry
Introduction
Water is necessary for our survival. It is one of the most important resources on our planet, and life cannot exist without this life-giving liquid.
This blog will cover the physical and chemical attributes of water.
The molecular structure of water
All substances are made of molecules, and water is no exception. Molecules are extremely small particles, and each molecule has two or more atoms. The molecular structure of water consists of two hydrogen atoms and one oxygen atom bonded together. In a water molecule, the oxygen atom acts as the central atom, with each hydrogen atom bonded to it (the formula is H20). Both oxygen and hydrogen atoms have electrons. Oxygen has an electronegative charge which in simple terms means all its protons attracts all the electrons more strongly than hydrogen giving the oxygen atom a slight negative charge and the hydrogen atoms a slight positive charge.
For a simplified explanation, imagine a family of three members: a mother
(representing the oxygen atom) and two children (representing the hydrogen
atoms) who are bonded together. The mother, being more dominant, pulls the
shared resources (electrons) closer to herself, due to its higher
electronegativity.
Why is water called the universal solvent
Water is called the universal solvent as water also pulls other substances apart, this process is called dissolution, meaning the process of dissolving something.
Trivia facts:
1. Molecules cannot be seen even with the most powerful microscopes.
2. A single drop of water contains several million trillion molecules.
Let’s understand a bit more about oxygen and hydrogen atoms.
1. Oxygen: Oxygen has 8 electrons, and it has 8 protons and 8 neutrons in the nucleus.
2. Hydrogen: Hydrogen has an electron, and has only a proton and no neutron in the nucleus.
Exception: There is an exception regarding the electrons of oxygen and hydrogen. Nearly every element (including oxygen) can both gain or lose electrons. This happens when it has a reaction with another atom, causing one of the atoms to lose electrons and the other to gain electrons.
The force of water:
The "forces of water" encompass various phenomena related to the properties and behaviour of water. This includes various forces such as cohesion, adhesion, buoyancy, etc. Let’s understand each of these water properties (meaning how water behaves and interacts with its surroundings) below:
1) Capillary action
Have you ever wondered how we pour water into the roots of plants and roots take water up instead of down? Isn’t it against the laws of gravity? Well, this happens because of capillary action. Capillary action is the ability of water to move upward against gravity. This is with the help of cohesion and adhesion in narrow spaces. Cohesion is a process in which water molecules stick together, and adhesion is a process of water molecules getting attracted to other substances.
Let’s take an example – the water level in all the tubes below is not the same. This is due to the capillary action. Adhesion of water to the walls of a vessel will cause an upward force on the liquid. If you observe the below image closely, the water levels in the smaller tubes are climbing faster. The reason for this is, the water molecules are closer to the walls, so they can stick to them more easily and climb up faster. On the contrary, the water molecules in larger tubes having to cover more distance to reach the walls, so it takes longer for them to climb up. It's like a shortcut for water in smaller tubes, making capillary action more effective. The height to which capillary action will take water in a tube (picture below) is limited by surface tension and, of course, gravity.
Picture credit: https://www.usgs.gov/special-
The
floating of an object is directly linked to buoyancy, which means it has less
mass. If an object has buoyancy, it can float but there is an exception to it,
surface tension (which I will cover in my next segment). Let’s understand buoyancy
principle through an example:
A ball can float. This is because it is less dense (which in simple terms means the space inside something). This is the reason why things float, but there is an exception to it, surface tension.
3) Surface tension
3) Surface tension
Normally, objects float because it has less mass but surface tension can help it float. This happens if something is so light that it floats. Example: Needle is another such example which demonstrates how surface tension can support the weight of an object like a needle placed carefully on the surface of water starts floating. Many insects use this to their advantage as they walk on the surface of water due to the principles of surface tension.
4) What happens when you freeze water?
Normally the atoms and molecules of liquids contract upon freezing, but water behaves differently. Even though water atoms are tightly packed upon freezing – its molecules are not. So, instead of contracting water expands. This is why ice is less dense, and the reason why ice floats on water.
Comments
Post a Comment