Question

choosing appropriate hypotheses
this lab question is: how can you distinguish a physical change from a chemical change?
which statements below are an appropriate hypothesis in response to this question? check all that apply

• if a substance changes state of matter (e.g., liquid to gas), then this is a physical change because the original properties of the substance have not changed.
• if a substance undergoes a physical change, then it will retain most of its original properties because no new substance is formed
• if a substance undergoes a chemical change, then it will not retain its original properties because a new substance is formed
• if a precipitate is formed when two substances are mixed, then a chemical change has taken place because precipitates are new substances.

Explanation:

An appropriate hypothesis for distinguishing physical and chemical changes should link observable changes to the core definitions: physical changes retain original properties (no new substance formed), while chemical changes form new substances with different properties.

1. The first statement correctly identifies state change as physical, tied to unchanged properties.
2. The second statement correctly links physical change to retained properties (no new substance).
3. The third statement correctly links chemical change to lost original properties (new substance formed).
4. The fourth statement correctly identifies precipitate formation (a new substance) as a chemical change.

All statements align with the criteria for valid hypotheses addressing the lab question.

Answer:

• [x] If a substance changes state of matter (e.g., liquid to gas), then this is a physical change because the original properties of the substance have not changed.
• [x] If a substance undergoes a physical change, then it will retain most of its original properties because no new substance is formed
• [x] If a substance undergoes a chemical change, then it will not retain its original properties because a new substance is formed
• [x] If a precipitate is formed when two substances are mixed, then a chemical change has taken place because precipitates are new substances.