Chemistry Chapter 15 and 16

surface tension

surface tension

A measure of how difficult it is to stretch or break the surface of a liquid

Water has a __________ surface tension

high

Surfactant

any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension

Micelle

lipid molecules that arrange themselves in a spherical form in aqueous solutions

How micelles are formed (rlly bad explanation at the moment)

Non polar hydrophobic attracted to non polar substance while hydrophilic polar head is attracted to the water. This is how soap works.

vapor pressure

the pressure exerted by a vapor over a liquid

water has a _____ vapor pressure

low

Why does water have a lower vapor pressure

Hydrogen bonds hold water molecules to one another so the tendency of these molecules to escape is low, and evaporation is slow.

Water is ___ than ice

denser

Why is water denser than ice?

When water freezes, water molecules form a crystalline structure maintained by hydrogen bonding. Solid water, or ice, is less dense than liquid water. Ice is less dense than water because the orientation of hydrogen bonds causes molecules to push farther apart, which lowers the density.

aqueous solution

a solution in which water is the solvent

Solvent

A liquid substance capable of dissolving other substances

Solute

A substance that is dissolved in a solution.

The Solution Process

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

Hydration

solution process with water as the solvent

Solvation

The process of surrounding solute particles with solvent particles to form a solution

Electrolyte

An ionic compound whose aqueous solution conducts an electric current

strong electrolyte

100% ionization

weak electrolyte

a solution that conducts electricity poorly because only a fraction of the solute exists as ions

Hydrate

A compound that has a specific number of water molecules bound to its atoms

efflorescent hydrate

A hydrate that has a vapor pressure higher than the pressure of water vapor in the air, the hydrate will lose its water of hydration.

hygroscopic hydrates

hydrated salts that have a low vapor pressure remove water from moist air to form higher hydrates

deliquescent compounds

remove sufficient water from the air to dissolve completely and form solutions

Suspension

A mixture from which particles settle out upon standing. The particles of a suspension are much larger then a solution. Heterogeneous (1000 nm or larger). Tyndall effect. Unstable against gravity. Can be filtered.

Colloid

heterogeneous mixture whose particles never settle (1 nm to 1000 nm). Spread throughout the dispersion medium. Colloids have particles smaller than suspensions and larger than solutions. Tyndall effect. No filter. Heterogeneous

Tyndall effect

Scattering of a light beam as it passes through a colloid

Brownian motion

the chaotic movement of colloidal particles, caused by collision with particles of the solvent in which they are dispersed

Emulsion

A colloidal dispersion of a liquid in a liquid. Quickly separates without presence of emulsifying agent.

Solution

A homogeneous mixture of two or more substances. Ions, atoms, and small molecules (0.1-1 nm). No Tyndall. Does not separate from gravity. homogeneous

coagulation of colloids

positive ions around lattice attract negative ions in layer and causes double ionic layer which prevents lattice from growing in size and precipitating. Clumps together to form heavier aggregates and precipitate from the dispersion.

What factors determine the rate at which a substance dissolves?

Stirring (agitation), temperature, the surface are of the dissolving particles [size(crush)], and concentration.

Kinetic Molecular Theory

based on the idea that particles of matter are always in motion

Solubility

A measure of how much solute can dissolve in a given solvent at a given temperature.

Miscible

Describes two liquids that are soluble in each other

Immiscible

liquids that are not soluble in each other

Factors affecting solubility

temperature and pressure

Temperature effect on solubility

Inversely proportional for gas solubility. The solubility of most solid substances increases as the temperature of the solvent increases. Solubilities of most gases are greater in cold water than in hot.

supersaturated solution

Contains more solute than it can theoretically hold at a given temperature.

Crystallization of supersaturated solution

Can be initiated if a very small crystal (seed crystal) of the solute is added

Pressure effect on solubility

Directly proportional for gas solubilities in liquids. Little effect on solubility of liquids and solids but strongly influences solubility of gases. As partial pressure of gas above solution increases gas solubility increases.

Henry's Law

At a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

Concentration

a measure of the amount of solute that is dissolved in a given quantity of solvent

Dilute solution

a solution that contains a small amount of solute

Concentrated solution

a solution containing a large amount of solute

Molarity

The number of moles of solute dissolved in one liter of solution

Dilution

Adding water to a solution in order to decrease the concentration

dilution equation

M1V1=M2V2

percent concentration (volume/volume)

Volume of solute/volume of solution x 100

percent concentration by mass

mass of solute/mass of solution x 100

colligative properties

A property that depends only upon the number of solute particles, and not upon their identity

Colligative Properties of Solutions

vapor pressure lowering, boiling point elevation, freezing point depression

Molality

the concentration of a solution expressed in moles of solute per kilogram of solvent

freezing point depression

The difference in temperature between the freezing point of a solution and the freezing point of the pure solvent

The magnitude of the freezing-point depression is proportional to

the number of solute particles dissolved in the solvent and does not depend upon their identity (molality)

boiling point elevation

The difference in temperature between the boiling point of a solution and the boiling point of the pure solvent

the magnitude of the boiling point elevation is proportional to

the number of solute particles dissolved in the solvent (molality)

freezing point depression equation

ΔTf = Kfm

boiling point depression equation

ΔTb = Kbm

van't Hoff factor

• total # of of particles in solution

• Ex: glucose is 1

• Ex: NaCl is 2 (breaks up into 2 ions)

vapor pressure lowering

due to the number of solute particles in solution and is a colligative property of solutions. The more solute particles there are dissolved (greater Molality) the less solvent particles that are able to evaporate and contribute to the vapor pressure.

The greater the molality

The greater the change (lowering) in the vapor pressure

vapor pressure lowering equation

ΔPvap = kvap x m x i

mole fraction

Ratio of the moles of that soulte to the total number of moles of solvent and solute

mole fraction equation

moles of solute/moles of solute + moles of solvent

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

A net movement of solvent from area of higher solvent concentration (lower solute concentration) to the area of lower solvent concentration (higher solute concentration)

Hypertonic/plasmolyzed

Having a higher concentration of solute than another solution.

Isotonic/flaccid

when the concentration of two solutions is the same

Hypotonic/turgid

Having a lower concentration of solute than another solution

reverse osmosis

A desalinization process that involves forcing salt-water through a membrane permeable to water but not to salt

osmotic pressure

the external pressure that must be applied to stop osmosis

osmotic pressure equation

π = iMRT