Final answer:
The substance with a melting point of 0°C, a boiling point of 100°C, and a density of 1.00 g/mL is likely water (H₂O), which can exist as both solid and liquid at its melting point, and as both liquid and gas at its boiling point.
Step-by-step explanation:
The substance with a melting point of 0°C, a boiling point of 100°C and a density of 1.00 g/mL could likely be water (H₂O). These physical properties are characteristic of water at standard atmospheric pressure. At its melting or freezing point, water can exist in both solid (ice) and liquid forms in equilibrium. Similarly, at the boiling point, liquid water and water vapor (gas) can coexist. The process of a solid melting is an endothermic process, where heat is absorbed, and freezing is exothermic, releasing heat. Likewise, boiling is endothermic while condensation (gas to liquid) is exothermic.