Final answer:
The behavior of substances at temperatures below 0°C, particularly mercury (Hg) and bromine (Br2), demonstrates phase changes and the phenomenon of sublimation, where materials can switch between different states of matter without passing through the liquid phase, as seen with carbon dioxide (CO2) and water (H2O).
Step-by-step explanation:
The question asked pertains to the behavior of substances at temperatures below 0°C, specifically referencing mercury (Hg) and bromine (Br2), which are the only two elements in a liquid state at room temperature.
However, the properties of water (H2O) and carbon dioxide (CO2) are also relevant as they showcase the phenomena of sublimation and phase changes at temperatures below 0°C, which is characteristic of certain elements and compounds when exposed to pressure variations or temperature changes. It highlights that at the melting point or boiling point, two phases can exist simultaneously, such as solid and liquid water at 0°C. It also elucidates that substances like CO2 can sublimate directly from solid to gas at 1 atm, bypassing the liquid phase, and ice will sublime under certain conditions even at temperatures below freezing, which has practical implications such as the gradual reduction of ice in a freezer.