Chemistry- Ch. 15: Water and Aqueous Systems

surface tension

the inward force, or pull, that tends to minimize the surface area of a liquid

surfactant

any substance that interferes with the H-bonding between water molecules, thereby reducing surface tension

Surfactant examples

detergents, soap, oil

Vapor Pressure

the ________ of water is remarkably low, due to H-bonding

Boiling Point

water has a very high _______, because of H-bonding

water is one of the few substances that has a ____ density as a solid than a liquid

lower

aqueous solution

water that contains dissolved substances

solvent

the dissolving medium

water is one of the best of these in the world- pure water doesn’t exist in nature

solute

the dissolved particles in a solution

solutions

homogenous mixtures, and stable throughout

not easily separated and will not settle out if left to stand

solvation

the process by which the positive and negative ions of an ionic solid become surrounded by solvent molecules

like dissolves like

water will dissolve most polar and ionic compounds because water itself is extremely polar

what doesn’t dissolve in water?

non-polar compounds

oil, grease, and gasoline (but they can dissolve each other)

electrolyte

a compound that conducts an electric current when it is in an aqueous solution or in the molten state

all ionic compounds are ______ because they dissociate into ions

non-electrolyte

a compound that does not conduct an electric current in either an aqueous solution or the molten state

many molecular compounds are ______

strong electrolytes

100% ionize

all or nearly all of the solute exists as ions

ions can move in the solution and easily conduct a current

salts, inorganic acids, inorganic bases

weak electrolytes

>1% ionize

conducts an electric current poorly because only a fraction of the solute in the solution exists as ions

organic acids and bases

Hydrate

a compound that contains water of hydration

Anhydrous

a substance that does not contain water

efflorescent hydrates

a hydrate with a vapor pressure higher than the pressure of water vapor pressure in the air

these will naturally lose their water over time

hygroscopic hydrates

a hydrate with a vapor pressure lower than the pressure of water vapor in the air

these will naturally gain water over time

used as desiccant

Desiccant

a compound used to absorb moisture from the air and create a dry environment

deliquescent compounds

compounds that absorb so much water from the air that they dissolve completely and become solutions

NaOH, gel packs in new shoes

Heterogenous mixtures

suspensions and colloids

suspensions

a mixture from which particles settle out upon standing

particles are much bigger than a solution

particles will settle out over time, they don’t stay suspended for long

particle size of 1 micrometer or bigger vs 1 nm or smaller for solutions

why are suspensions heterogenous?

at least 2 substances can be identified

colloids

particle size between 1 nm and 1 micrometer

can be solid, liquid, or gas

glue, paint, aerosol sprays, and smoke

Tyndall effect

the scattering of visible light by colloidal particles

brownian motion

the chaotic movement of colloidal particles. this is caused by collisions of colloid particles with particles in the dispersion medium

prevents settling of colloids