Vapour Pressure

Vapour Pressure
Vapour Pressure

Vapor is a type of fluid that does not contain any visible particles. It can be found in various places including the air we breathe. Vapor occurs naturally in clouds and water. When the smoke rises from your fireplace, it is actually a form of vapor.

When steam condenses, it forms droplets of water which are then called fog. Fog also happens to occur during cloud formation. When you blow your nose, you are releasing vapor out of your body because the inside lining of your nose has moist mucous membranes and tiny hairs.

Vapor is formed when heat changes the state of a substance from a solid or a liquid to a gaseous state. The process takes place in three stages:

In the first stage, the compound gets heated to its boiling point.

Vapour is not a new concept but now the demand has increased a lot due to its various benefits. You may know the term an air freshener and some people even use it to improve the smell of the room. There is no doubt that it works really well for the purpose for which it was created, but there are many other ways through which it helps us in improving different aspects of life. Here are some of the amazing health benefits of using a vaporizer.

Vaporizers help in relieving stress

There is nothing more relaxing than taking deep breaths and inhaling fresh and pure oxygen. But when you feel stressed, all this activity becomes quite difficult for you and it creates problems like headaches or high blood pressure. To avoid such situations you should try to take a breath of clean air every 15 minutes during the day. A vaporizer

Vapour Pressure
Vapour Pressure

will work wonders on your mind and body by increasing the production of serotonin. Serotonin is the hormone responsible for reducing anxiety levels and decreasing tension.

You will sleep better

When you are feeling anxious or tired, it affects your sleeping pattern and disturbs your night. To overcome these issues, you can use a vaporizer to provide a peaceful atmosphere inside the house. Your body gets relaxed and the brain receives enough amount of oxygen so that you get a sound and healthy sleep.

Boost metabolism

The more you breathe, the more active your metabolic rate and if you have a sluggish metabolic rate then it leads to weight gain. When you use a vaporizer at home you inhale the pure air and thus increase the level of energy within you and boost up metabolism. As a result, you lose extra pounds from your body without having any side effects.

Improve digestion

If you have been experiencing stomach discomfort for a long time, it might be because of your digestive system. You may not know that the vapors of vaporizers improve our gastrointestinal functions. It also helps to eliminate toxins and gas present in the body. Thus, it provides relief from constipation as well.

Reduce cholesterol

There are certain foods that contain fats and they cause an unpleasant sensation in the stomach. These things act like obstacles to proper digestion.

Vapour Pressure

What Is Vapour Pressure?

Vapor pressure occurs when there is a difference in temperature between two phases. In other words, liquid water molecules are moving around but they can’t escape because their surrounding air molecules are too warm. The result is that the liquid forms bubbles and becomes unstable.

When vapor pressure exists, a substance can be said to be supersaturated. This means that more of the substance is present than would normally be expected for a given amount of space. In fact, this excess of a substance in a gas can lead to something called ‘rain’ which causes condensation on the outside of objects.

Supersaturation isn’t just found in nature. It happens inside our homes too. For example, you might find that your cupboards contain things such as eggs or salt crystals. This is because liquids tend to form layers inside containers.

The vapor pressure is the quantity of gas that evaporates from a liquid or solid substance in one atmosphere. In other words, vapor pressure means the amount of vapor that the solid or liquid will release.

The main reason for this question arises when someone wants to know what is vapour pressure and how it works. Well, it is very simple and easy if you understand the process of evaporation.

Vaporization is a chemical reaction that takes place in the air above the surface of any liquid or solid. Vaporization involves converting all atoms and molecules into gaseous form. Thus, you may say that the vapors are nothing but gases.

As the temperature increases, there is an increase of vapor pressure; thus vapor pressure plays a vital role in the development of life. At lower temperatures, the atmospheric pressure is greater than the boiling point and vapor pressure of water and ice is zero. But as the temperature rises, the vapor pressure decreases and it reaches 0K (or 273.15 K) for the maximum.

If the heat source is removed, then the vapor pressure will decrease because the heat will not be available and the gas particles will return to their original state. It is the same principle that governs the behavior of steam under normal conditions.

The vapor pressure of a pure substance is less than its saturated vapour pressure and is called the sub-saturated vapor pressure. The difference between the two pressures is known as the super saturation vapour pressure. This pressure is the vapour pressure of the substance at the temperature of interest.

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Characteristics of Vapour Pressure

Vapour Pressure

When it comes to liquids, they behave differently depending on their state. For example, water boils when the surrounding air is very hot, but freezes when the outside temperatures drop drastically. However, a common feature to all liquids is that they evaporate into a gas. If you’ve ever seen a glass pipe containing a substance such as marijuana, then you know that vaporization happens quickly.

If you think back to elementary school science lessons, then you may remember the process of evaporation being explained by the concept of ‘vapor pressure’. Vapor pressure is a measure of how much pressure is needed to force a given volume of a liquid to change its phase. This can be used to predict certain characteristics of a liquid.

One thing to note about this property is that it varies with temperature.

Vapour Pressure of Liquid-liquid Solutions

The term ‘vapour pressure’ refers to the amount of force that is required to keep a given volume of air from escaping. If you take two containers filled with water, put them next to each other and leave both for a few minutes, you will find out that there has been a difference in the level of the fluid inside. The container on top is now higher than the lower one. This means that there must be more of the substance under less pressure.

In order to understand how this works, we need to look at a liquid-liquid solution. A mixture of different fluids usually creates a new type of solvent called a mixed phase. In our example, we have two kinds of fluid: one is water and another is alcohol. When they are combined, a sort of solution forms.

A liquid-liquid solution is a mixture containing two immiscible liquids with different densities, where the lower density phase occupies the uppermost portion. The relative proportions of these components affect the properties and behavior of this type of solution.

Vapor pressure is the tendency of the vapor formed when boiling a liquid to leave the surface area. The vapor pressure of a given material is usually defined as the difference between its saturation vapor pressure and the actual vapour pressure at the temperature in question. This is the amount of force required to keep liquid away from the solid wall until the equilibrium condition is achieved.

If you see the diagram below, you will understand how vapor pressure affects the movement of the molecules.

The higher the vapor pressure, the more difficult it is for the molecules to escape from the liquid. Thus the process of evaporation starts easily and the rate of removal increases over time. On the other hand, if the vapor pressure is low then the molecules are less likely to be removed from the liquid. So, there won’t be much mass loss.

Let us now find out the vapor pressures of some common solvents like alcohols and ethers:


Formaldehyde – 3.5 mm Hg

Methanol – 4.7 mm Hg

Ethanol – 1.8 mm Hg


Isopropyl Alcohol (C3H8O) – 14.4 mm Hg

Propylene Glycol (C3H6(OH)(CH2.3. – 17.9 mm Hg

Tetrahydrofuran (C4F10. – 27.1 mm Hg


Ethylene Oxide – 2.9 mm Hg

Butane (C4H10. – 5.1 mm Hg

Acetonitrile – 15.

Vapour Pressure of Pure Liquids

Vapor pressure, also known as vaporization, is a property of a liquid in which the amount of energy required to remove a single molecule from a bulk quantity is less than the total internal energy available to that molecule. Vapor pressure is defined as the force per unit area acting upon a substance and it represents how much force must be exerted to maintain a certain level of concentration of molecules within a container.

When a liquid is heated, it starts to turn into a gas because the bonds holding together the individual atoms are breaking down more easily. This means that the bond strength becomes weaker, so when they’re no longer held tightly enough, the atoms separate from each other. As this happens, all of the original properties (size, shape, weight) disappear. The same thing happens with a solid.

The vapor pressure is the driving force that helps the liquid to evaporate at a constant temperature. If you want to know the vapor pressure of pure liquids, then the first thing you should do is find the boiling point. The boiling point is the temperature when the liquid starts to boil. After the boiling point, you will find the boiling liquid temperature which is the highest temperature possible. This temperature is called the critical temperature. In this stage, the substance is unstable and is not stable.

There is another way of calculating the vapor pressure, if you have the mass and density values of the liquid then you can calculate the vapor pressure using the ideal gas law.

Ideal Gas Law

P = nRT

Where P – Vapor pressure in Pa

n – Number of moles of the substance

R – Universal gas constant

T – Temperature

If you follow these three points then you can easily calculate any vapour pressure value. Let us see the calculations for various substances.

Hydrogen: 1.2 kPa (at STP)

Carbon Monoxide: 0.085kpa

Oxygen: 0.23kpa

Nitrous Oxide: 6.35kpa

Ammonia: 3.6kpa

Sulfur Dioxide: 5.7kpa

Methane: 4.0kPA

Formaldehyde: 8.4kpa

Chlorine: 11.1kpa

In the case of water, the vapor pressure is 760mmHg.

The Vapour pressure of alcohols is between 2 and 20 times higher than that of water. That is why, if we drink too much alcohol then it will lead to dehydration. The most common cause of death due to drinking is a heart attack.

If you are looking to know more about the vapor pressure of pure liquids, then I recommend you read the blog.

Is Vapour Pressure Proportional to Temperature?

The law of vaporization states that the amount of steam generated is directly proportional to the absolute temperature. It’s also known as the ‘vapor pressure of water’. If you boil water, then it will generate a lot more steam than if you heat it up slowly.

What does this mean? Well, for example, when you are cooking food on a stove, you need to turn the heat down because if the air inside your kitchen starts getting hot, the air outside your kitchen can become very humid. This means your home will start feeling stuffy and uncomfortable. And this is something you don’t want in your house!

So, how do you keep the humidity level low so that your house doesn’t feel damp? One way to solve this problem would be to use an extractor fan.

Vapor Pressure Examples

The term “vapor pressure” is often used in the chemical industry. But, if you don’t know exactly what it means, then this may be confusing. So here’s a quick explanation.

Vapor pressure is a measure of how much gas will dissolve into a liquid or the amount of a solvent that a substance can hold without changing its state. In other words, the higher the vapor pressure, the greater the volatility of the compound. The lower the vapor pressure, the less volatile the compound is and vice versa.

For example, water has a low vapor pressure because most of the time, we are dealing with anhydrous substances (no water). However, methanol, ethanol, benzene, toluene, ethyl acetate, etc.


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