The boiling point of a substance is the temperature at which it changes from a liquid to a gas. At this temperature, the vapor pressure of the liquid equals the atmospheric pressure surrounding it. Different substances have different boiling points, which can be influenced by factors such as pressure and the presence of impurities. For example, the boiling point of water at sea level is 100 degrees Celsius (212 degrees Fahrenheit). However, at higher altitudes, where atmospheric pressure is lower, the boiling point of water decreases. This means that food may take longer to cook in boiling water at high elevations.