What is the Boiling Point of Water?

What is the Boiling Point of Water?

The following article provides information regarding the boiling point of water, and the associated factors that affect or alter it.
Boiling point of a substance is the exact temperature reading, at which the specific substance changes its liquid state to vapor or gaseous state. In other words, boiling point is the temperature, wherein the liquid and vapor states of a substance remain in equilibrium. Every element or substance has a standard boiling point, based on the material makeup and component particles. This particular temperature fluctuates with respect to the surrounding environmental conditions, such as altitude and atmospheric pressure.

We boil water every day for some or the other purposes, such as making beverages (tea, coffee, etc.), cooking food, sterilizing medical equipment, etc. However, it is to be noted that the boiling point changes with several factors.

Explanation

Boiling point is defined as the temperature when the vapor pressure of a substance or liquid is similar to the external or atmospheric pressure surrounding the solution. A further increase in temperature from this point, is taken up by the liquid as the latent heat of vaporization, which helps in changing the liquid to a gaseous state. This way, water heated at a temperature higher than boiling point gets evaporated as steam.
  • Water Boiling Point in Celsius: It is 100° C at 1 atmospheric pressure. Air bubbles form on the sides of vessel at the time of heating.
  • Water Boiling Point in Fahrenheit: It is 212° F, when measured at 1 atmospheric pressure. It is observed that every 500 feet increase in elevation of altitude corresponds to 1 degree drop in the water boiling point.
Factors Affecting the Boiling Point of Water

The change in the boiling point with reference to certain aspects is an interesting subject for science fair projects. It is understandable that a standard atmospheric pressure is maintained, when we talk about this topic. In general, the boiling point of a solution changes with respect to the pressure surrounding the liquid at that particular time. And this change in boiling temperature is directly proportional to the pressure.

Speaking about water boiling point, it is lower at higher altitudes where the atmospheric pressure is low, as compared to the standard boiling point measured at 1 atmosphere or 760 mm. of mercury. This explains the phenomenon of distilling water at a much lower temperature in laboratories. In such cases, the pressure is maintained at minimum (e.g., in vacuum flasks), which ultimately makes the water boil at a temperature lower than the standard boiling point. Thus, the pressure is usually mentioned while writing the boiling point of a specific liquid.

Another factor that elevates the water boiling point is the presence of solutes or other compounds. This is known as boiling point elevation, and it is a basic colligative property in chemistry. To be more precise, the boiling point in pure form is lower than that of salt water, or any other solution prepared by adding compounds. You can experiment this on your own at home or in laboratory. Likewise, boiling point of a pure solvent is lower than its solution.

If you compare boiling point of water with hydrogen sulfide or other hydrogen compounds, you will find it relatively high. This increased temperature reading is due to strong hydrogen bonds that tightly hold the water molecules together.