Freezing Point And Vapour Pressure: Detailed Facts

This article will study the detailed facts of freezing point and vapour pressure and their relationship.

The freezing point is a certain temperature range of a substance at which both liquid and solid substances will be at equilibrium. At this phase, their vapour pressure will be equal. If you add a non-volatile solid to the volatile liquid, the combination of solvents will have less vapour pressure.

First, let us learn about the freezing point.

Freezing Point: Meaning

It is mainly a process in which certain physical and chemical changes occur.

It is indicated as a change of state of any substance or material to a different form when certain factors affect it. If there is a transition of material from liquid to solid in the equilibrium stage at a specific temperature point, it is considered the freezing point of water.
It is also considered the temperature point at which both the solid and liquid state of the substance exists together in the equilibrium state.

Let us now study the detailed explanation of factors affecting the freezing point.

Factors affecting the Freezing Point of a substance

The major factors that affect the freezing point of a substance are as follows,

If the intermolecular forces of the liquid matter are strong and valid, then its freezing point increases.
Similarly, if the intermolecular force that acts between the molecules of the liquid matter is weak, it will decrease the freezing point of the liquid.
From the above two factors, we can infer that the intermolecular forces of a substance directly affect the freezing point. Hence, they are proportional to one another.

freezing point and vapour pressure — **Image Credit: Pixabay free images**

Now let us know about vapour pressure.

Vapour Pressure: Meaning

The simple way in which a vapour pressure can be defined is as follows,

If we place any liquid substance inside a vessel and start to heat it continuously, then the molecules of this substance move in random directions at different speeds. It occurs due to the different kinetic energies of the molecules. Here it causes the vapour pressure that will affect other properties of the liquid.

To study the effects of vapour pressure on freezing point.

How does vapour pressure affect the freezing point?

Except for water, in all the other cases, if there is a slight increase or decrease in vapour pressure, there will be a slight rise or fall in the freezing point of the substance.

There are some specific solvent molecules for which the surface of molecules will be able to vaporize when pressure acting on it decreases gradually. At this point, the boiling point will gain a rise. The other consequence of the freezing and vapour pressure is both decreases together for some solvents except in the case of water, and here we can see if there is a rise in pressure, it lowers the freezing point of water.

It’s time to understand why pressure increases the freezing point.

Why does pressure increase the freezing point?

There is a direct relation between the increase of pressure and the freezing point that helps change matter.

When we try to apply some high pressure on the gaseous substance, the gas molecules transform into a liquid state under these circumstances. If we again apply high pressure on the same substance, the attraction forces convert it from liquid to a solid-state. It has a direct relationship between the rate of crystallization and the increase in vapour pressure, and both lead to an increase in freezing point.

Now to study the effect of decrease of pressure.

Does pressure decrease the freezing point?

Only in the case of water, we can observe the decrease in freezing point when the vapour pressure increases.

If there is an increase in vapour pressure, the water atoms spread in a wider area during the bond formation or transition from the liquid state to the solid crystalline state. This action is the main reason why ice appears less dense than the water, leading to ice floatation. This freezing action that causes the spreading of molecules indicates that when the pressure is applied leads to a lowering of the freezing point of water.

To understand the relationship between the freezing point and pressure.

What is the relationship between the freezing point and pressure?

Certain things play a major role in relating vapour pressure and freezing point.

Firstly, the change in vapour pressure of a substance will reduce or increase the freezing point of any material.
Except in the case of water, in all the other substances, pressure decreases, affecting the substance’s temperature and reducing its freezing point.
There are solvents for which the surface of molecules will be able to vaporize only when pressure acting on it reduces gradually. At this point, the boiling point will gain a rise. The other consequence of the freezing and vapour pressure decreases together for some solvents.

To study the phase of substances under pressure.

Does water freeze faster or slower under pressure?

Whether water freezes faster or slower depends on the increase and decrease in vapour pressure.

When you keep water in a freezer with normal vapour pressure, then the rate of air pressure certainly affects the freezing of water. If the pressure rate is higher, it reduces the freezing point of water and vice versa in the case of lower pressure.

To study the facts of the increase in vapour pressure.

What happens to the freezing point when vapour pressure increases?

As the vapour pressure increases, there will be a decrease in the freezing point.

The freezing point of water will fall or reduces as there is an increase in pressure due to the arrangement of molecules in this process. As the atmospheric pressure rises, this pressure restricts water molecules to undergo proper arrangement. But if water transforms into a solid phase through freezing, it can be considered.

To study the occurrence of freezing.

Frequently Asked Questions | FAQs

Why does the freezing point of water always reduce as there is a rise in pressure?

It is already known that with the rise in atmospheric pressure, the freezing point of liquids reduces to a certain extent.

The freezing point of water always reduces as there is an increase in pressure due to the arrangement of molecules during this process. As the atmospheric pressure rises, this pressure restricts water molecules to undergo proper arrangement. But in the case of water transforming into a solid phase through freezing, it can be considered.

Which factor reduces the freezing point of water?

The two main factors or substances that alter the freezing point of water are salt and sugar.

During clearing the ice blocked roads, people generally spread slat over the area so that it melts the ice by lowering its freezing point. It is the physical and chemical change that causes the transformation of water into another state of matter. In the same way, sugar is a popular substance that reduces the freezing point.

Can we say that freezing point and vapour pressure increase together?

There will be a rise in freezing point for most of the substances, but only to a certain extent.

Only in the case of water, we can see a fall in freezing point, but other than this, all the other substances gain a rise in freezing point when there is an actual gain in pressure. This special property of expansion of water causes the ice to float. The main thing that we should observe here is as the pressure increases, the melting point decreases.

How are freezing point and vapour pressure related to one another?

There is an inverse relationship between the freezing point and the vapour pressure of a substance.

There are some solvent molecules for which the surface of molecules will be able to vaporize when pressure acting on it reduces suddenly. At this point, the boiling point will gain a rise. The other consequence of the freezing and vapour pressure decreases together for some solvents.

What factor increases the freezing point of water?

The prominent factor that increases the temperature of the freezing point of water is alcohol.

In general, the freezing point of the purest form of water is 0 °C. In recent days, scientists have invented a method to increase the freezing point of water by adding drops of alcohol to it. The other method discovered to increase the freezing point is through electricity.

In what way does pressure affect the freezing point of a substance?

If we consider in case of water, then the freezing point of the substance reduces when the atmospheric pressure or vapour pressure rises.

If the vapour pressure increases, the water atoms spread in a wider area during the bond formation or transition from liquid to solid crystalline state. This action makes ice appear less dense than the water, leading to the floatation of ice. This freezing action that causes the spreading of molecules indicates that when the pressure is applied leads to a lowering of the freezing point of water.

Does increasing vapour pressure decrease water’s freezing point or any other liquid substance?

The increase or decrease in vapour pressure always affects the freezing point of water or any other liquid.

When the vapour pressure increases, the actual process is the disarrangement of water molecules. It is why water cannot freeze at its exact preferred temperature but freezes below that. Therefore, we can conclude that only in the case of pure water the freezing point decreases on the rise in vapour pressure. It is not true for other liquid substances.

What are the different changes in a Freezing Point of a substance?

There are mainly two different changes that occur during the freezing point.

The two processes are physical and chemical, which occur during the freezing of any substance. These factors can even cause a change in the freezing point. By adding two or more soluble substances, we can change the freezing point from the physical aspect, while coming to the chemical aspect, we can apply pressure on the substance.

Also, please click to know about 6+ Fluid Pressure Example or Freezing Point And Boiling Point.

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Raghavi Acharya

I am Raghavi Acharya, I have completed my post-graduation in physics with a specialization in the field of condensed matter physics. I have always considered Physics to be a captivating area of study and I enjoy exploring the various fields of this subject. In my free time, I engage myself in digital art. My articles are aimed towards delivering the concepts of physics in a very simplified manner to the readers.