Which statement correctly describes water's chemical nature?

• A. Water cannot be broken down chemically.
• B. Water easily decomposes into hydrogen and oxygen under sunlight.
• C. Water is a reactive chemical that breaks down spontaneously.
• D. Water is composed of silicon and oxygen only.

Answer: (A)

Understanding that water is a chemical compound that can be decomposed into its elements with energy is what this item is testing. Water (H2O) is made of two hydrogen atoms and one oxygen atom bonded together. Those bonds can be broken when energy is supplied, such as in electrolysis, which splits liquid water into hydrogen gas and oxygen gas. Water is quite stable under normal conditions, so it doesn’t spontaneously break down in everyday situations, and sunlight alone doesn’t readily drive its decomposition. Also, water’s composition is not silicon and oxygen; it’s hydrogen and oxygen. So the idea that water cannot be broken down isn’t correct, and the others mix up conditions or composition.