Question

1. elements can be broken down into simpler substances by chemical means.
2. water is made of hydrogen and oxygen atoms bonded together.
3. carbon dioxide and water are examples of elements.
4. molecules can contain atoms of the same or different elements.

Explanation:

• 12: Elements are pure substances that cannot be broken down into simpler substances by chemical means. For example, gold (\(Au\)) remains gold no matter what chemical reaction it undergoes.
• 13: The chemical formula of water is \(H_2O\), which means each water molecule consists of two hydrogen (\(H\)) atoms and one oxygen (\(O\)) atom bonded together.
• 14: Carbon dioxide (\(CO_2\)) is made of carbon (\(C\)) and oxygen (\(O\)) atoms, and water (\(H_2O\)) is made of hydrogen (\(H\)) and oxygen (\(O\)) atoms. Elements are substances made of only one type of atom. So, they are compounds, not elements.
• 15: For example, \(O_2\) (oxygen gas) has atoms of the same element (oxygen), and \(CO_2\) has atoms of different elements (carbon and oxygen).

Answer:

1. False
2. True
3. False
4. True