Why is water considered an excellent solvent for many substances?

Introduction / Context:
Water is often called the universal solvent because it can dissolve a wide variety of substances, especially ionic compounds and many polar molecules. This property is crucial in biological systems, chemistry, and environmental science. For example, nutrients, gases, and waste products are transported in aqueous solutions within living organisms. This question asks why water is such an excellent solvent. Understanding the molecular reason for this property helps explain many phenomena, from how salts dissolve to how biochemical reactions occur in cells.

Given Data / Assumptions:

• The options propose different reasons related to boiling point, reactivity, molecular size, and polarity with hydrogen bonding.
• We assume basic knowledge of molecular structure and chemical bonding.
• Solvent quality refers to the ability to dissolve many ionic and polar substances.
• We use standard chemistry concepts for polarity and hydrogen bonding.

Concept / Approach:
A water molecule has a bent shape and unequal sharing of electrons between oxygen and hydrogen atoms, which makes it polar. The oxygen end has a partial negative charge, and the hydrogen ends have partial positive charges. This polarity allows water molecules to attract and surround ions and other polar molecules, forming hydration shells. Water molecules can also form hydrogen bonds among themselves and with solutes that have electronegative atoms such as oxygen or nitrogen. These interactions help pull solute particles apart and keep them dispersed, which is the essence of dissolving. Therefore, the correct reason is related to polarity and hydrogen bonding, not low boiling point, non reactivity, or large molecular size.

Step-by-Step Solution:
Step 1: Recall that water has a bent molecular shape with oxygen being more electronegative than hydrogen. Step 2: Recognise that this creates partial charges on different parts of the molecule, making water a polar molecule. Step 3: Understand that polar water molecules can attract and stabilise ions, such as sodium and chloride, by surrounding them with oppositely charged ends. Step 4: Recall that water molecules form hydrogen bonds with each other and with polar solutes, helping to separate and disperse solute particles in solution. Step 5: Compare this explanation with the answer choices and identify the option that refers to polarity and hydrogen bonding as the key reasons. Step 6: Conclude that water is an excellent solvent mainly because its molecules are polar and can form hydrogen bonds with many solutes.

Verification / Alternative check:
Another way to verify is to think about substances that do not dissolve well in water, such as non polar oils. Since oils are non polar, they do not interact strongly with polar water molecules, so water cannot effectively separate their molecules. This contrast highlights the importance of polarity. Many ionic compounds such as common salt dissolve easily in water because the charged ions are strongly attracted to the partial charges on water molecules. Laboratory experiments show that when salt is added to water, the ions disperse and the solution conducts electricity, demonstrating that water has separated and stabilised the ions, consistent with the polarity and hydrogen bonding explanation.

Why Other Options Are Wrong:
A very low boiling point is not the main reason for good solvent properties. Water actually has a relatively high boiling point for its molecular size due to hydrogen bonding, so this statement is inaccurate and does not explain its ability to dissolve substances.

Water is not completely non reactive. It participates in many chemical reactions, such as hydrolysis and redox processes, so claiming total non reactivity is wrong and does not explain solvent behaviour.
Large and heavy molecules are not necessarily good solvents. In fact, water is a small molecule. Its excellent solvent properties come from polarity and hydrogen bonding, not from size or mass, so this option is incorrect.

Common Pitfalls:
Students may confuse properties such as high boiling point, surface tension, or specific heat with solvent ability and choose options that mention boiling or reactivity. Others might think that being unreactive automatically makes a substance a good solvent, which is not true. Another pitfall is not understanding what a polar molecule is and therefore not appreciating why water interacts strongly with ions and polar solutes. To avoid these mistakes, focus on the idea that like dissolves like: polar solvents dissolve polar and ionic solutes, and water is strongly polar with the ability to form hydrogen bonds.

Final Answer:
Water is considered an excellent solvent primarily because water molecules are polar and can form hydrogen bonds with solutes.