When vapor pressure increases, does the boiling point increase or decrease?


The vapor above the liquid exerts a pressure like any gas. As the vapor pressure increases the boiling point decreases.

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Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. 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 (or a solid). A substance with a high vapor pressure at normal temperatures is often referred to as volatile.

The vapor pressure of any substance increases non-linearly with temperature according to the Clausius–Clapeyron relation. The atmospheric pressure boiling point of a liquid (also known as the normal boiling point) is the temperature at which the vapor pressure equals the ambient atmospheric pressure. With any incremental increase in that temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure and lift the liquid to form vapor bubbles inside the bulk of the substance. Bubble formation deeper in the liquid requires a higher pressure, and therefore higher temperature, because the fluid pressure increases above the atmospheric pressure as the depth increases.

Chemistry Thermodynamics Physics

A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.

A phase of a thermodynamic system and the states of matter have uniform physical properties.

Gases Pressure

Chemical engineering is a branch of chemistry and engineering that applies the physical sciences (e.g., chemistry and physics) and/or life sciences (e.g. biology, microbiology and biochemistry) together with mathematics and economics to production, transformation, transportation and proper usage of molecules, chemicals, materials and energy. Modern chemical engineers are concerned with processes that convert raw-materials or chemicals into more useful or valuable forms. In addition, they are also concerned with pioneering valuable materials and related techniques – which are often essential to related fields such as nanotechnology, fuel cells and biomedical engineering. Within chemical engineering, two broad subgroups include design, manufacture, and operation of plants and machinery in industrial chemical and related processes ("chemical process engineers") and development of new or adapted substances for products ranging from foods and beverages to cosmetics to cleaners to pharmaceutical ingredients, among many other products ("chemical product engineers").

The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high-pressure has a higher boiling point than when that liquid is at atmospheric pressure. In other words, the boiling point of a liquid varies depending upon the surrounding environmental pressure. For a given pressure, different liquids boil at different temperatures.

Vapor Boiling

Water vapor or aqueous vapor is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is lighter than air and triggers convection currents that can lead to clouds.

Water vapor is a potent greenhouse gas along with other gases such as carbon dioxide and methane.


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