From Models to Materials · Paper 1 — Free Chemistry HL Practice Questions

Three solids — sodium chloride (NaCl), iodine (I₂), and copper (Cu) — are tested for electrical conductivity at room temperature. Only one conducts. Which statement correctly identifies the conducting solid and explains why?

When liquid bromine, $\text{Br}_2$, is placed in a sealed container at room temperature, it reaches equilibrium with its vapour. The container is then cooled until some vapour condenses. Which statement correctly describes the change in both the arrangement and the average kinetic energy of the bromine particles as condensation occurs?

A drop of ethanol ($\text{C}_2\text{H}_5\text{OH}$) placed one hand feels noticeably colder than a drop of water ($\text{H}_2\text{O}$) placed on the other hand as each evaporates. Which statement best explains this observation?

A sealed syringe contains liquid water at $25\ ^\circ\text{C}$. The plunger is pulled back until the internal pressure drops to $2.0\ \text{kPa}$. The vapour pressure of water at $25\ ^\circ\text{C}$ is $3.2\ \text{kPa}$. Which statement best explains why the liquid water vaporizes completely under these conditions?