Question

3 what makes a change a chemical change instead of a physical one? a the substance changes between solid, liquid, and gas b the atoms rearrange to form a new substance c the size or shape of the substance changes d the composition of the substance stays the same

Explanation:

• Option A: Changes between solid, liquid, and gas (phase changes) are physical changes. For example, water boiling (liquid to gas) is a physical change as the chemical composition (\(H_2O\)) remains the same.
• Option B: In a chemical change, atoms rearrange to form new substances. For instance, when hydrogen (\(H_2\)) and oxygen (\(O_2\)) react to form water (\(H_2O\)), new chemical bonds are formed and a new substance is created.
• Option C: Changes in size or shape (e.g., cutting a piece of paper) are physical changes. The chemical composition of the paper (mainly cellulose) does not change.
• Option D: If the composition of a substance stays the same, it is a physical change. Like dissolving salt (\(NaCl\)) in water - the \(NaCl\) can be recovered by evaporation, showing no new substance is formed.

Answer:

B. The atoms rearrange to form a new substance