1. Why is water ‘the universal’ solvent?
Water is commonly known as the universal solvent since it is able to dissolve a huge range of substances or solutes. The ability by water to dissolve many different substances is mainly due to its molecular structure as well as its polar nature. The water molecule is made up of two hydrogen atoms combined to one oxygen atom. There is a negative charge at the oxygen atoms and a positive charge at the hydrogen atoms of the water molecule. This is because the electrons within the molecule are not evenly distributed across the entire molecule. The uneven distribution of elections across the different atoms in water creates the polarity of the water molecule. The polarity of water molecules allows them to easily attract other charged molecules which causes easy dissolving. For example, substances such as salt or sugar are attracted to water molecules to form hydrogen bonds.
The process of a substance dissolving in water involves water molecules surrounding the solute being dissolved and breaking the bonds between the solute molecules. When water comes into contact with a solute, the polar water molecules surround the solute particles and form hydrogen bonds with them. 104
This pulls them apart from one another forming a solution with water. The solute molecules are broken down into individual particles which are them evenly dispersed within the water which is called dissolving.
The ability of water to dissolve a solute depends on the nature of the solute and also interaction with water molecules. Substances that are polar or charged, such as salts, acids and alcohols are generally soluble in water. This is because they interact with water molecules through hydrogen bonding. Nonpolar substances, such as oils and fats, on the other hand are generally insoluble in water. This is because they lack the polarity necessary for hydrogen bonding.
It is important to note that the process of dissolving a solute in water involves an increase in entropy. When a solute is being dissolved in water, the solute particles are dispersed throughout the water. This increases the randomness or disorder of the system. For example, when adding sugar too tea or coffee, stirring helps dissolving to occur faster. This is because stirring increases the entropy which helps the dissolution process. 362