Question

choose the best answer.
2.15) a compound must have different joined together.
a. elements b. atoms c. molecules
write t for true or f for false. if false, rewrite the statement to make it true.
2.16) water is a compound and a molecule.
2.17) all compounds are molecules, but not all molecules are compounds.

Explanation:

• 2.15: A compound is a substance formed when two or more different elements chemically combine. Atoms can be of the same element (e.g., \(O_2\) has two oxygen atoms, but it is an element, not a compound). Molecules can be of elements (e.g., \(H_2\)) or compounds.
• 2.16: Water (\(H_2O\)) is made of two hydrogen and one oxygen atoms (different elements), so it is a compound. A molecule is a group of atoms bonded together. \(H_2O\) is also a molecule.
• 2.17: Compounds are made of different elements' atoms bonded together (so they are molecules). But molecules like \(O_2\) (made of same - element atoms) are not compounds.

Answer:

• 2.15: A. elements
• 2.16: T
• 2.17: T