Water is often called the "universal solvent" because it can dissolve a wide variety of substances, more than any other liquid. However, it's important to note that the term "universal" is a bit of an exaggeration. While water can dissolve many substances, it cannot dissolve everything. For example, it does not dissolve oils or fats.

The key to water's dissolving power lies in its polarity. Here's how it works:

* Polarity: Water molecules are bent, with the oxygen atom being slightly negative and the hydrogen atoms being slightly positive. This uneven distribution of charge makes water a polar molecule.

* Attraction: When a polar molecule like water encounters another polar molecule or an ionic compound, the opposite charges attract. The positive end of the water molecule attracts the negative end of the other molecule, and vice versa.

* Dissolving: This attraction can overcome the forces holding the other substance together, causing it to break apart and become surrounded by water molecules. This is the process of dissolving.

Examples:

* Salt (NaCl): When salt dissolves in water, the positive sodium ions (Na+) are attracted to the negative oxygen end of water molecules, while the negative chloride ions (Cl-) are attracted to the positive hydrogen ends. This weakens the ionic bonds in the salt crystal, allowing it to dissolve.

* Sugar (C12H22O11): Sugar is a polar molecule with many oxygen atoms. The oxygen atoms in sugar can form hydrogen bonds with the hydrogen atoms in water, leading to its dissolution.

Non-polar substances and water:

Non-polar substances like oils and fats have an even distribution of charge. They are not attracted to the polar water molecules and therefore don't dissolve in water. This is why oil and water separate.

In summary, water's polarity is the key factor in its ability to dissolve many substances. The positive and negative ends of water molecules attract and interact with other polar molecules and ionic compounds, breaking them down and causing them to dissolve.