When two hydrogen atoms combine with one oxygen atom, the result is a water molecule, which is a(n):

When two hydrogen atoms combine with one oxygen atom, the result is a water molecule, which is a(n):

• A. Atom
• B. Mixture
• C. Element
• D. Compound

Answer: (D)

When different elements join in a fixed ratio and form a substance with new properties, that substance is a compound. Water is two hydrogen atoms bonded to one oxygen atom, so it has a definite composition and can be broken down into its elements only through chemical reactions. An element is made of one kind of atom, and an atom is a single unit of an element, so neither describes water. A mixture is a physical blend where the components keep their own properties and can be separated by physical means, which isn’t the case for water since the hydrogen and oxygen are chemically bonded. Water is also a molecule, but given these options, the best label is compound.

When different elements join in a fixed ratio and form a substance with new properties, that substance is a compound. Water is two hydrogen atoms bonded to one oxygen atom, so it has a definite composition and can be broken down into its elements only through chemical reactions. An element is made of one kind of atom, and an atom is a single unit of an element, so neither describes water. A mixture is a physical blend where the components keep their own properties and can be separated by physical means, which isn’t the case for water since the hydrogen and oxygen are chemically bonded. Water is also a molecule, but given these options, the best label is compound.