Final answer:
Water's ability to remain a liquid at room temperature, unlike similarly sized molecules such as methane, is due to strong hydrogen bonding. These bonds also cause ice to be less dense than liquid, allowing it to float, which is vital for ecological systems and life in general.
Step-by-step explanation:
The ability of water to remain a liquid at room temperature, in contrast to similarly sized molecules like methane which are gases, is due to the presence of strong hydrogen bonding. This intermolecular force contributes significantly to the unique physical properties of water. For instance, each water molecule can form hydrogen bonds with up to four neighboring molecules due to its bent shape and the presence of two hydrogen atoms. This extensive bonding network gives water its high boiling point, surface tension, and the ability to act as a solvent for many biological processes.
Additionally, water's density decreases when it turns solid (ice). This is because the hydrogen bonds arrange the molecules in a crystalline structure that occupies more space than the liquid phase, creating an anomaly where the solid form floats on the liquid. These properties of water are essential for life, affecting climates, ecological systems, and the physiological processes of living organisms. Hydrogen bonding is therefore critical to the biochemical functions of water in nature and within the human body.