# Relationship between atmospheric pressure and boiling point

### What Happens to a Boiling Temperature as Pressure Decreases? | Sciencing

A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. In other words, the boiling point of a liquid. Boiling point, temperature at which the pressure exerted by the surroundings upon a liquid is at which the vapour pressure is equal to the standard sea-level atmospheric pressure ( climate: Relation between temperature and humidity. The higher the pressure the higher is the boiling point of a liquid. To explain this simply: as you increase the temperature of a liquid.

### thermodynamics - Relationship between boiling point and pressure - Physics Stack Exchange

The connection between pressure and temperature is explained by a property called vapor pressure, a measure of how readily molecules evaporate from a liquid. That's because increased ambient temperature makes it hard for vapor to escape the liquid, and more energy is needed to boil. Vapor Pressure The vapor pressure of a substance is the pressure of vapors exerted on a container of the substance at a particular temperature; this is true for both liquids and solids.

For example, you half fill a container with water, pump out the air and seal the container. The water evaporates into the vacuum, producing a vapor that exerts a pressure. At room temperature, the vapor pressure is 0.

## Boiling point

When the temperature increases, the pressure also increases. Good Molecular Vibrations At any temperature above zero kelvin, the molecules in a substance vibrate in random directions.

Molecules vibrate faster as temperatures increase. The molecules do not all vibrate at the same speed, however; some move slowly while others are very fast.

At any given temperature, if a compound's normal boiling point is lower, then that compound will generally exist as a gas at atmospheric external pressure. If the compound's normal boiling point is higher, then that compound can exist as a liquid or solid at that given temperature at atmospheric external pressure, and will so exist in equilibrium with its vapor if volatile if its vapors are contained.

If a compound's vapors are not contained, then some volatile compounds can eventually evaporate away in spite of their higher boiling points.

Boiling points of alkanesalkenesethershalogenoalkanesaldehydesketonesalcohols and carboxylic acids as a function of molar mass In general, compounds with ionic bonds have high normal boiling points, if they do not decompose before reaching such high temperatures. Many metals have high boiling points, but not all. Very generally—with other factors being equal—in compounds with covalently bonded moleculesas the size of the molecule or molecular mass increases, the normal boiling point increases.

• How do atmospheric pressure and elevation affect boiling point?

When the molecular size becomes that of a macromoleculepolymeror otherwise very large, the compound often decomposes at high temperature before the boiling point is reached. Another factor that affects the normal boiling point of a compound is the polarity of its molecules. As the polarity of a compound's molecules increases, its normal boiling point increases, other factors being equal.

Closely related is the ability of a molecule to form hydrogen bonds in the liquid statewhich makes it harder for molecules to leave the liquid state and thus increases the normal boiling point of the compound. Simple carboxylic acids dimerize by forming hydrogen bonds between molecules.