Have you ever seen water freezing and boiling at the same time? It is known as the triple point of water. When water is ice, liquid, and gas simultaneously, it becomes a triple point. The triple point is a combination of water stages at which water as liquid state solid as ice state and vapor at gas coexist at a perfect temperature. This point is 0.01 degrees Celsius or 273.16 Kelvin. At this temperature, only you can see water at different stages at the same time.
Water can boil and freeze at the same time
You must be thinking that water freezes at 0 degrees Celsius. Then how come it boils? It’s because the triple point can only exist in a vacuum or space. Not that vacuum cleaner! Vacuum chamber, to know how this occurs, we need to understand enthalpy vaporization. This term says that boiling is not the main point to heat water.
There is another way also, the atmospheric pressure. The pressure caused by air is called atmospheric pressure. The atmospheric pressure change with the attitude. It can only happen in vast large areas. Water boils at hundred degrees Celsius, but it is incomplete. It is defined as: “The boiling point of water is hundred degrees Celsius at one atmospheric pressure.”
Now, what does this one atmospheric pressure mean? Water doesn’t always need to boil at hundred degrees Celsius. You can boil it to whatever temperature you want. But you also have to change the atmospheric pressure like water can boil at 80 degrees Celsius at 6.9 Atmospheres.
- The atmospheric pressure is directly proportional to the temperature.
Let’s take the example of Earth. The air has atoms. The atoms also contain some weight. So the gravity will also cause on them. The air is mostly downwards near the surface than the Sky because of the weight of gravity. It means the atmospheric pressure will be more on the ground than the Sky. As the temperature is directly proportional to the atmospheric pressure, the ground pressure will be high, and the temperature will also be high. That’s why the Mountains are cold because they are located upwards.
How can water boil and freeze at the same time?
As in space or vacuum, there is very less or about no pressure. So if we put water in space or vacuum, it will start boiling. There are two factors on which the water boils.
Factor number one is When water boils, the molecules of water in the liquid state become vapor. Then the water molecules give their heat to the vapor molecules and energy also. After some time, all the heat is gone with energy, and a vacuum sucks very quickly. So this process is done very quickly. It is gone totally so that it will become ice.
As the heat molecules give their energy surroundings and make it equivalent, the surroundings also give their cold air to the boiling water and keep on boiling. If there is no pressure or very little pressure, the substance will go directly from solid to gas.
The second factor, air, also goes when the vapors are going from the water to the vacuum. Then there is no air inside the water, and water needs to compress, and heat forms ice.
There’s a time at 0.01 degrees Celsius when water is in all three stages. In thermodynamics, any pure substance can exist in three phases: a solid, a liquid, or gas.
- Solid as Ice.
- Liquid as water state.
- Gas as vapor state.
That’s the time which is known as the triple point. We can show these phases using a pressure-temperature diagram called a PT diagram.
The graph shows the different phases of a pure substance with pressure and temperature.
- With pressure P on the vertical axis.
- The temperature T on the horizontal axis.
The three phases are separated from each other by so-called separation lines. There is a melting line between the solid and the liquid phase. The sublimation line lies between the solid and the gaseous phase. And the vaporization line between the liquid and the gaseous phase. The triple point is the location where all of these lines need. It is specified by a certain pressure and temperature what is characteristic of each substance.
If a pure substance is like the specified temperature and pressure values, all three phases will be present simultaneously. One says that the three phases coexist.
Pure water has a trigger point temperature of 0.01 degrees Celsius and a triple point pressure of 611.5 Pascal. This is the same as about 0.6% of the normal atmospheric pressure. At this point, water will exist both as ice and liquid.
If you are very curious about the triple point, you can make it yourself at home. For this, you need a vacuum pump, thermometer, pressure chamber, and magnesium sulfate anhydrous.
- First, you need to add magnesium sulfate anhydrous in the water. Magnesium sulfate and just makes the process of boiling slow so that it does not harm the chamber.
- Now, put a thermometer in the water to measure the temperature.
- Put your beaker in the chamber and use the vacuum pump to remove all the air from it. And make the pressure low.
Now you can see the different states of water at a time!
IUPAC, Compendium of Chemical Terminology, 2nd ed., “Triple point.”
James Thomson, “A quantitative investigation of certain relations between the gaseous, the liquid, and the solid states of water-substance.”