Pressure

(noun)

The amount of force applied over a given area divided by the size of the area.

Related Terms

Examples of Pressure in the following topics:

  • Pressure and Free Energy

    • Gibbs free energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure.
    • When a system changes from an initial state to a final state, the Gibbs free energy (ΔG) equals the work exchanged by the system with its surroundings, minus the work of the pressure force.
    • Gibbs energy (also referred to as ∆G) is also the chemical potential that is minimized when a system reaches equilibrium at constant pressure and temperature.
    • As such, it is a convenient criterion of spontaneity for processes with constant pressure and temperature.
    • Therefore, Gibbs free energy is most useful for thermochemical processes at constant temperature and pressure.

  • Osmotic Pressure

    • Osmotic pressure is the pressure needed to nullify the effects of osmosis and is directly influenced by the amount of solute in the system.
    • The height difference between the two sides can be be converted into pressure to find the osmotic pressure exerted on the solution by the pure solvent.
    • Osmotic pressure is the pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
    • Osmotic pressure can also be explained as the pressure necessary to nullify osmosis.
    • The osmotic pressure is the pressure required to achieve osmotic equilibrium.

  • Vapor Pressure of Nonelectrolyte Solutions

    • When a solute is added to a solvent, the vapor pressure decreases.
    • The decrease in entropy difference lowers the vapor pressure.
    • Raoult's law states that the vapor pressure of an ideal solution is dependent on the vapor pressure of the pure solvent and the mole fraction of the component present in the solution.
    • For an ideal solution, equilibrium vapor pressure is given by Raoult's law:
    • Calculate the vapor pressure of a nonelectrolyte solution using Raoult's law

  • Changes in Volume and Pressure

    • This principle can be applied to changes in temperature, concentration, volume, and pressure.
    • As can be seen, a reduction in volume yields an increase in the pressure of the system, because volume and pressure are inversely related.
    • In order to compensate for the increasing pressure and decreasing volume of the system, the new equilibrium state will favor conditions that decrease the pressure in the system.
    • A schematic of the pressure due to the collisions of gas particles with the walls of a vessel
    • Evaluate the effect of pressure on the equilibrium of a chemical reaction

  • Dalton's Law of Partial Pressure

    • Dalton's Law of Partial Pressure states the total pressure exerted by a mixture of gases is equal to the sum of the partial pressure of each individual gas.
    • Dalton's Law (also called Dalton's Law of Partial Pressures) states that the total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases.
    • What is the total pressure inside the container?
    • What is the partial pressure of He?
    • We now define the partial pressure of each gas in the mixture to be the pressure of each gas as if it were the only gas present.

  • Boyle's Law: Volume and Pressure

    • What is the final pressure of the gas?
    • The new pressure (P2) remains unknown.
    • How does compressing a gas affect its pressure?
    • The moving wall converts the effect of molecular collisions into pressure and acts as a pressure gauge.
    • What happens to the pressure when the volume changes?

  • Solid to Gas Phase Transition

    • It is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point (the temperature and pressure at which all three phases coexist) in its phase diagram.
    • Also, at pressures below the triple point pressure, an increase in temperature will result in a solid being converted to gas without passing through the liquid region.
    • This is because the pressure of their triple point is very high and it is difficult to obtain them as liquids.
    • There are other solids whose vapor pressure overtakes that of the liquid before melting can occur.
    • Such substances sublime; a common example is solid carbon dioxide (dry ice) at 1 atm of atmospheric pressure.

  • Liquid to Gas Phase Transition

    • Pvap is known as the "equilibrium vapor pressure", or simply as the "vapor pressure" of the liquid.
    • The variation of vapor pressure with temperature is not linear.
    • This is because the liquid can be heated less in order for its vapor pressure to equal the atmospheric pressure.
    • If the vapor pressure of the drop is greater than the partial pressure of vapor in the gas phase, the drop will evaporate.
    • The variation of vapor pressure with temperature is not linear.

  • SI Units of Pressure

    • On a given day, the atmospheric pressure is 770 mm Hg.
    • What is the pressure in pascals?
    • What does pressure mean?
    • How is gas pressure caused?
    • How can you measure pressure?

  • Vapor Pressure of Electrolyte Solutions

    • The vapor pressure of an electrolytic solution is dependent on the ratio of solute to solvent molecules in a solution.
    • Vapor pressure is the pressure exerted by a vapor in equilibrium with its condensed phase, either liquid or solid, at a particular temperature.
    • Vapor pressure of a liquid is a colligative property.
    • To better visualize the effect of solute on the vapor pressure of a solution, consider a pure solvent.
    • This pure solvent has a certain vapor pressure associated with it.