A student records the following observations for eight separate processes carried out at constant pressure in the laboratory.
1. Liquid ethanol boils at 78 °C.
2. An iron nail left outdoors gradually develops a reddish-brown surface.
3. Ice at 0 °C melts in an insulated beaker.
4. A white precipitate forms instantly when solutions of barium chloride and sodium sulfate are combined.
5. Solid iodine sublimes when gently warmed, forming a violet vapor.
6. Metallic sodium reacts vigorously with liquid water, producing bubbles of gas.
7. Carbon dioxide gas is compressed from 1.0 atm to 5.0 atm at 25 °C.
8. A sample of copper(II) sulfate pentahydrate turns white when heated, releasing water vapor.
For the purpose of this question all processes occur in closed systems except where gases are explicitly released.
(a) Sort the eight processes into two groups—those that represent chemical changes and those that represent physical changes—based solely on particulate‐level reasoning. Present your answer in a clearly labeled table.
(b) For ONE process you identified as a chemical change and ONE process you identified as a physical change, explain your classification in terms of what happens to intramolecular bonds and intermolecular forces.