Question

chemical and physical changes
part b
while studying chemical and physical changes, students added salt to a glass of water. they stirred the salt until it dissolved and could no longer be seen. \thats a chemical change,\ sarah stated. do you agree?
explain.
a yes, it is a chemical change because something new is formed
b no, it is a physical change. it is salt and water and you cant get the salt back by boiling off the water
c yes, it is a chemical change because there was a change to the appearance of one of the components, the salt
d no, it is a physical change. a chemical change...

Explanation:

To determine if dissolving salt in water is a chemical or physical change, we recall the definitions:

• Physical change: Alters appearance/state but not chemical identity; no new substance forms, and the original substance can be recovered (e.g., boiling water to retrieve salt).
• Chemical change: Forms a new substance with distinct properties (irreversible by simple means).

• Option A: Incorrect. Dissolving salt does not form a new substance (salt + water → salt water, which is a mixture, not a new compound).
• Option B: Partially correct about it being physical, but the claim "you can’t get the salt back" is wrong—boiling water (evaporation) does recover salt.
• Option C: Incorrect. A change in appearance (salt dissolving) is a physical change, not chemical (no new substance).
• Option D (implied correct, though text is cut off): Dissolving salt is physical because the salt’s chemical identity (NaCl) remains, and it can be recovered (e.g., evaporation). The key is no new substance forms, so it’s physical.

Answer:

D (assuming the full option D states: "No, it is a physical change. A chemical change forms a new substance, but dissolving salt only mixes it with water; the salt can be recovered by evaporating the water.")
(Note: If D’s full text aligns with the physical change definition, it is correct. The other options are flawed: A/C claim chemical change (wrong), B incorrectly says salt can’t be recovered.)