Question

henry mixed salt and water together in a cup until he observed a clear solution. he measured the mass of the solution. then he placed the cup outside for several sunny days during the summer. after a week he observed that only solid salt remained in the cup and the mass had decreased. henry concluded that a physical and a chemical change occurred in this investigation. which statements correctly defend or dispute his conclusion? he is correct. dissolving salt in water is a physical change, but evaporating the water is a chemical change. formation of a solid is evidence that a chemical change occurred. he is correct. evaporation is a physical change, but dissolving salt in water is a chemical change. the formation of a solid is evidence of a chemical change.

Explanation:

To solve this, we analyze the processes:

Step 1: Analyze Dissolving Salt in Water

Dissolving salt (\( \text{NaCl} \)) in water is a physical change because the salt ions (\( \text{Na}^+ \), \( \text{Cl}^- \)) disperse in water but no new substance is formed (the salt can be recovered by evaporation).

Step 2: Analyze Evaporating Water

Evaporating water is also a physical change (liquid water \(
ightarrow \) gaseous water; no new substance is formed).

Step 3: Evaluate Henry’s Conclusion

Henry claims a chemical change occurred, but both dissolving and evaporation are physical changes. So his conclusion is incorrect. Let’s check the statements (assuming the third option argues his conclusion is wrong, e.g., "He is incorrect. Dissolving salt in water and evaporating water are physical changes; no chemical change occurred.").

1. Dissolving salt in water: Physical change (salt disperses, no new substance).
2. Evaporating water: Physical change (state change, no new substance).
3. Henry’s conclusion (chemical change) is wrong because both processes are physical.

Answer:

(Assuming the correct option is the one stating Henry is incorrect, e.g., "He is incorrect. Dissolving salt in water and evaporating water are physical changes; no chemical change occurred.")