In basic chemistry, water (H2O) is correctly classified as which of the following types of substance?

Introduction / Context:
This question tests a fundamental classification in chemistry: the difference between elements, molecules, and compounds. Water is one of the most familiar substances, and students must be able to describe it correctly using these terms. The key idea is that a single substance can be both a molecule and a compound at the same time, so understanding how the definitions overlap is important.

Given Data / Assumptions:

• Water has the chemical formula H2O.
• Hydrogen and oxygen are elements.
• Molecule is defined as two or more atoms chemically bonded together.
• Compound is defined as a pure substance formed when atoms of different elements combine in a fixed ratio.
• We assume standard school level definitions of these terms.

Concept / Approach:
An element is a substance made of only one type of atom, such as pure hydrogen gas or pure oxygen gas. A molecule refers to a group of two or more atoms held together by covalent bonds; these atoms may be of the same element or different elements. A compound is a pure substance made of atoms of different elements bonded in a fixed ratio. Because water consists of two hydrogen atoms and one oxygen atom covalently bonded, each water particle is a molecule. Since these atoms are of different elements in a fixed 2:1 ratio, water is also a compound. Therefore, both the terms molecule and compound apply to water.

Step-by-Step Solution:
Step 1: Check whether water is an element. Water contains hydrogen and oxygen, so it is not a single element. Step 2: Check whether water is a molecule. H2O consists of three atoms bonded together, so it is definitely a molecule. Step 3: Check whether water is a compound. Because it contains different elements (H and O) in a fixed ratio, water is a compound. Step 4: Combine the correct descriptions. Water is both a molecule and a compound, so the answer must include both.

Verification / Alternative check:
Chemistry textbooks usually list water among common molecular compounds. They explain that all compounds whose particles are discrete molecules, such as water, methane, and carbon dioxide, can be called both molecules and compounds. Only substances made from one element, such as O2 or N2, are molecules but not compounds. Since water always appears with both hydrogen and oxygen, it fits both definitions. This confirms that the most precise description from the options is the one that includes both terms.

Why Other Options Are Wrong:
Option A: Element is incorrect because water contains more than one type of atom. Option B: Molecule alone is incomplete; although true, it does not fully reflect that water is also a compound. Option C: Compound alone is also incomplete; water is a compound whose smallest unit is a molecule.

Common Pitfalls:
Learners often think that being a compound and being a molecule are mutually exclusive categories, so they pick only one label. Another common mistake is to confuse water with hydrogen or oxygen gases and call it an element. Remember that a molecular compound like water is both a molecule and a compound, while an elemental molecule like O2 is only a molecule and not a compound.

Final Answer:
Water is correctly described as Both B & C, that is, it is both a molecule and a compound.