Vapor pressure is the pressure within a gas or vapor in a closed container. It is affected by temperature, container size, and molecular bond strength. As temperature increases, the rate of evaporation increases until it reaches an equilibrium point. The size of the container and molecular bond strength also affect vapor pressure.
By definition, vapor pressure is the amount of pressure within a vapor or gas when the substance is in a state of equilibrium. In other words, when a liquid or solid is in a closed container and some molecules evaporate while others return to a liquid or solid state, the pressure that can be measured inside that container is relative to the vapor. Vapor pressure is expressed in terms of atmospheres (atm) and can be affected by changes in temperature, container size and molecular bond strength.
As water turns to steam and the steam is trapped in a container, the pressure of the water vapor will increase until it reaches an equilibrium point. At that point, the rate of evaporation equals the rate of condensation. In other words, when vapor is captured in an enclosed area, the temperature rise resulting from an increase in vapor leads to condensation within the container. The water molecules are trapped within the walls of the container and cannot escape. As a result, the molecules begin to collide, bond and return to a liquid state.
As the temperature increases, the rate of evaporation also increases. The molecules will continue to evaporate until the equilibrium point is reached. The equilibrium point is also known as the saturation vapor pressure, because the vapor is completely saturated. The condensation process begins once the equilibrium point is reached.
The size of the vessel in which the vapor is held also affects the pressure changes. The more vapor there is within a contained area, the more pressure there is within that same area. For example, imagine a growing crowd of people crammed into a small room. As more people enter the room, people will move closer, because the size of the room doesn’t change. In the case of steam, the more molecules that enter a container, the closer the molecules get and the higher the pressure of the steam increases.
In addition to temperature variations and space constraints, the type of bonds in the molecular structure can determine whether the vapor pressure will be relatively high or low. Basically, the easier it is for bonds to form, the faster the rate of condensation will be and, therefore, the break-even point will occur relatively quickly. If the equilibrium state is reached quickly, the vapor pressure will be relatively low. Alternatively, if the bonds are weak, the molecule will bind slowly. It will take longer for the evaporation rate to equal the condensation rate and the molecule will have a high vapor pressure.
Protect your devices with Threat Protection by NordVPN
