Which of the following best describes how chemical compounds are formed?

• A. By the evaporation of elements into gases
• B. By the decomposition of a single element into simpler substances
• C. By the physical mixing of elements without any chemical change
• D. By the chemical combination of two or more elements in fixed proportions

Answer: (D)

Verified step by step guidance

1. Understand that chemical compounds are substances formed when two or more elements chemically combine, meaning their atoms bond together through chemical reactions.
2. Recognize that the formation of compounds involves a chemical change, not just a physical mixing or phase change like evaporation.
3. Recall that elements cannot decompose into simpler substances because they are the simplest form of matter; decomposition applies to compounds, not elements.
4. Note that compounds have fixed proportions of elements, meaning the ratio of atoms is constant and specific for each compound.
5. Conclude that the best description of how chemical compounds are formed is by the chemical combination of two or more elements in fixed proportions.