1. Pressure:
* Lower Pressure, Lower Boiling Point: This is the biggest factor after heat. Think about how water boils at a lower temperature on top of a mountain. That's because the air pressure is lower, allowing water molecules to escape into the air more easily.
* Higher Pressure, Higher Boiling Point: Conversely, pressure cookers work because they trap steam, increasing the pressure inside. This forces water molecules to stay in the liquid state, requiring higher temperatures to boil.
2. Impurities:
* Dissolved Salts and Minerals: Adding salt to water raises the boiling point slightly. This is why seawater boils at a slightly higher temperature than fresh water.
* Other Substances: Adding other substances like sugar or even dirt can also influence the boiling point, but the effect is usually small.
3. Surface Tension:
* Clean Surfaces: Water boils more easily on smooth, clean surfaces.
* Impurities or Roughness: Impurities or rough surfaces can hinder bubble formation, requiring slightly higher temperatures to boil.
4. Nucleation Sites:
* Bubbles Need a Place to Start: Bubbles of vapor need a place to form, called nucleation sites. These can be tiny air bubbles, scratches on the container, or impurities in the water.
* Superheating: If there are no good nucleation sites, water can sometimes get hotter than its normal boiling point without boiling – a phenomenon called superheating.
In Summary:
While heat is the primary driver of boiling, factors like pressure, impurities, and surface tension can all influence the temperature at which water transitions from a liquid to a gas.
