Gen Chem 2 - Exam 1

Boiling point

when the vapor pressure of a liquid increases enough to equal the external atmospheric temperature

supercritical fluid

a state of matter where a substance is heated and pressureized so much that it becomes a hybrid of a liquid and a gas at the same time. It can flow through solid materials like gas, but it can dissolve things like a liquid.

Capillary action

how liquids like water climb up narrow spaces or tinny tubes against the pull of gravity.

surface tension

the tendency of a liquid's surface to act like a stretchy skin or thin elastic film that resists an external force

Cohesive force

the attractive pull between identical molecules that causes them to stick together.

adhesive force

the attractive pull between molecules of different substances that makes them stick together

Condensation

the process where gas turns back into a liquid

triple point

the specific temperature and pressure where a substance's solid, liquid, and gas phases all exist together at the same time in balance.

Critical point

a specific temperature and pressure where a liquid and its gas become completely identical, ending the boundary line between them.

van der Waals forces

weak attractive forces between neutral molecules or atoms

Dipole-dipole attraction

an electrostatic pull between the positive end of one polar molecule and the negative end of another polar molecule.

Vapor pressure

the force exerted by a gas when it sits in balance above its liquid or solid form in a closed container.

Dispersion (London) force

a temporary, weak attraction between molecules caused by the random, uneven movement of electrons.

Vaporization

the physical process where a substance changes from a liquid or solid into a gas

Dynamic equilibrium

when a chemical reaction goes forward and backward at the exact same speed.

Viscosity

a measure of a fluid's resistance to flow

Freezing point

the specific temperature at which a liquid changes into a solid

Normal boiling point

the temperature at which a liquid boils when the pressure above the liquid is 1 atm

Hydrogen bonding

an extra-strong magnetic pull between the hydrogen of one molecule and an oxygen, nitrogen, or fluorine of another.

Phase diagram

a simple map that shows whether a substance is a solid, liquid, or gas at any given temperature and pressure.

Induced dipole

a temporary magnetic-like separation of charge that happens in a normally neutral atom or molecule when it gets close to a nearby charge.

Polarizability

how easily an atom or molecule's electron cloud can be distorted or squished by an outside electrical charge.

Instantaneous dipole

a temporary, uneven distribution of electrons that happens by pure chance in an atom or molecule.

Intermolecular forces

the "sticky" forces of attraction that pull separate molecules toward each other.

Enthalpy of Vaporization

the energy needed to turn a liquid into a gas → endothermic

Enthalpy of Condensation

the energy released when a gas turns into a liquid → exothermic

“Beading”

when a liquid pulls away from a surface and forms distinct rounded droplets

“Wetting”

when a liquid spreads out evenly and flatly over a solid surface

How does freeze-drying work?

Foods are dehydrated by sublimation at pressures below the triple point for water.

What does specific heat do during a phase transition?

the standard concept of specific heat is not used because the temperature of the substance remains constant.

Sublimation (phase transition)

solid to gas

Deposition (phase transition)

gas to solid

At high altitudes

there is less air pressure → less energy (temperature) to boil 80°

At low altitudes

there is high air pressure → more energy (temperature) to boil 100°

Polarity

unequal sharing of electrons between atoms