Final answer:
The temperature at which a liquid turns to gas is known as the boiling point, a physical property, exemplified by water's boiling point of 100°C at 1 atm pressure.
Step-by-step explanation:
The temperature at which a liquid turns to gas is known as the boiling point. The boiling point is a physical property and is defined as the temperature at which a substance's vapor pressure equals the surrounding atmospheric pressure, causing the substance to form bubbles and change to vapor (or gas) throughout the liquid. An example is water, which has a boiling point of 100°C at 1 atmosphere of pressure (normal boiling point). When a liquid reaches its boiling point, it undergoes a phase change from liquid to gas. This phase change is also influenced by the surrounding pressure as gases are strongly affected by pressure. Therefore, a higher pressure would result in a higher boiling point, and vice versa.