# What is Vapor Pressure?

##### Joseph Hebert
Owner at - HVAC Buster

Joseph is an HVAC technician and a hobbyist blogger. He’s been working as an HVAC technician for almost 13 years, and he started blogging just...Read more

Vapor pressure is the name given to the partial pressure of a gas above a liquid. The molecules of the gas are in constant motion, colliding with each other and with the walls of their container. In a closed container, the molecules have nowhere to go but back into the liquid, so their average kinetic energy (and thus their temperature) remains constant.

Vapor pressure is the pressure of a gas in equilibrium with its non-gaseous form. In other words, it is the pressure of a gas that is in equilibrium with its liquid or solid form. The vapor pressure of a given substance varies depending on the temperature; as the temperature increases, so does the vapor pressure.

For example, water has a much higher vapor pressure at 100°C than it does at 0°C. The vapor pressure of a substance can be measured using a variety of methods, including manometry and spectroscopy. It is an important property because it allows us to calculate the boiling point of a liquid; when the vapor pressure equals atmospheric pressure, the liquid will boil.

Vapor pressure is also used to measure evaporation rates and to predict phase changes in mixtures containing multiple substances.

## What is Vapor Pressure Simple Definition?

Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its non-vapor phases. The equilibrium vapor pressure is an indication of a liquid’s evaporation rate. It relates to the tendency of particles to escape from the liquid.

A substance with a high vapor pressure at normal temperatures is often referred to as volatile. The term can also be applied to solids and liquids, but only when in contact with a gas or other vapors with which they are not chemically reacting and are in full thermal contact.

## What is Vapor Pressure And Example?

Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. For example, water has a vapor pressure at room temperature and standard atmospheric pressure. The higher the temperature, the higher the vapor pressure.

At the boiling point, the vapor pressure is equal to the ambient atmospheric pressure.

## What is the Meaning of Vapor Pressure in Chemistry?

In chemistry, vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. The vapor pressure is an indication of a liquid’s evaporation rate into a gas. The higher the vapor pressure of a liquid at a given temperature, the faster it will evaporate.

The equilibrium vapor pressure of a substance is the pressure at which its vapour phase is in equilibrium with its solid or liquid phase. The substance’s vapour phase can be above, below or at atmospheric pressure and the solid or liquid phase can be either sublimating (evaporating without passing through the liquid state) or not. For example, water has an exceptionally high vapour pressure even though it cannot form a gas (it sublimely evaporates) below 100°C; this is because there are many molecules of water in each drop that can escape as vapour and because they are very close together so have little intermolecular attraction holding them back.

The concept of vapourpressure explains why liquids boil: when we heat water to 100°C (its boiling point), we are actually increasing its vapourpressure to equal atmospheric pressure; so at this temperature more molecules than ever before are able to escape from the surface of the water into the atmosphere as steam/water vapour.

## What is Vapor Pressure of a Liquid?

The vapor pressure of a liquid is the pressure exerted by the molecules of the liquid when they are in equilibrium with the molecules of the gas phase. The higher the vapor pressure, the more volatile the liquid is.

## Water Vapor Pressure

Water vapor pressure is the partial pressure of water vapor in a given space. It is often expressed as a percentage of the total atmospheric pressure. The higher the water vapor pressure, the more water vapor there is in the air.

When the air is saturated with water vapor, the water vapor pressure is said to be 100%. The amount of water vapor that can be held in air varies depending on temperature. Warm air can hold more water vapor than cold air.

That’s why you often see fog or clouds when warm air moves over cold bodies of water. The reverse can also happen. When cold air moves over warmer bodies of land, you may see condensation in the form of dew or frost.

Knowing the local conditions of humidity and temperature can help you predict weather patterns.

## Vapor Pressure And Boiling Point Relationship

As anyone who has ever cooked knows, water boils at 100 degrees Celsius (212 Fahrenheit). But why does it boil at this temperature? The answer has to do with vapor pressure.

Vapor pressure is the pressure of a gas in equilibrium with its liquid or solid form. When the vapor pressure of a liquid is greater than the atmospheric pressure, the liquid will boil. For water, this happens at 100 degrees Celsius because that is when its vapor pressure becomes equal to atmospheric pressure.

The boiling point of a substance is therefore directly related to its vapor pressure. substances with high vapor pressures have low boiling points (e.g. mercury) while those with low vapor pressures have high boiling points (e.g. water). This relationship can be explained by the kinetic theory of gases which states that as molecules gain more energy, they move faster and are more likely to escape from the surface of a liquid into the gas phase.

So there you have it! The next time someone asks you why water boils at 100 degrees Celsius, you can tell them all about vapor pressure and the relationship between boiling point and molecular kinetic energy!

## Vapor Pressure Will Increase With:

As temperatures increase, the molecules in a liquid gain more energy and move faster. They collide more frequently with the walls of their container and escape from the surface of the liquid into the air above it. This process is called evaporation.

The rate of evaporation increases as the temperature rises because there are more high-energy molecules present to escape from the surface. The increased evaporation causes an increase in vapor pressure.

## Which is True of Vapor Pressure

Vapor pressure is the pressure of a substance in its gaseous form. The higher the vapor pressure, the more volatile the substance. Vapor pressure is affected by temperature; as temperature increases, so does vapor pressure.

There are two types of vapor pressure: absolute and relative. Absolute vapor pressure is the actual pressure of the gas itself, while relative vapor pressure is the partial pressure of the gas in a mixture. Vapor pressure can be measured using a variety of methods, including manometers, barometers, and mercury-in-glass thermometers.

## Conclusion

Vapor pressure is a measure of the amount of water vapor present in air. The higher the vapor pressure, the more water vapor present in the air. Vapor pressure is affected by temperature, humidity, and wind speed.

The higher the temperature, the higher the vapor pressure. The higher the humidity, the lower the vapor pressure. The higher the wind speed, the lower the vapor pressure.

Joseph is an HVAC technician and a hobbyist blogger. He’s been working as an HVAC technician for almost 13 years, and he started blogging just a couple of years ago. Joseph loves to talk about HVAC devices, their uses, maintenance, installation, fixing, and different problems people face with their HVAC devices. He created Hvacbuster to share his knowledge and decade of experiences with people who don’t have any prior knowledge about these devices.