Final answer:
Altitude impacts water's boiling point due to atmospheric pressure differences; higher altitudes mean lower pressure and thus a lower boiling point. This can affect cooking times and methods at different elevations. Changes in altitude also slightly affect freezing points, although this is less significant compared to the boiling point variations.
Step-by-step explanation:
Altitude affects the freezing, melting, and boiling points of water due to changes in atmospheric pressure. As altitude increases, the atmospheric pressure decreases, leading to a lower boiling point for water. At sea level, where atmospheric pressure is around 760 mmHg, water boils at 100°C. However, at higher altitudes such as in Denver, Colorado (approximately 1600 meters above sea level), the atmospheric pressure drops to about 640 mmHg, and water boils at approximately 95°C. The summit of Mount Everest, with significantly lower atmospheric pressure, will see boiling points much lower still. Likewise, the freezing point depression and boiling point elevation can be influenced by variations in atmospheric pressure caused by altitude.
Pressure cookers can compensate for the lower boiling points at high altitudes by increasing the pressure inside the cooker, which raises the boiling point of water. Conversely, the freezing point of water is also affected by altitude, but since it is more predominantly influenced by the presence of solutes—a concept known as freezing point depression—a change in altitude will not have as significant an effect unless the atmospheric conditions are substantially altered.