The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid is affected by several factors, including the atmospheric pressure, the purity of the liquid, and the presence of dissolved substances. The boiling point of a liquid at sea level is typically given in units of degrees Celsius (°C) or Kelvin (K). For example, the boiling point of water at sea level is 100 °C or 373 K.