Chem. 7+8

Pressure

A force exerted against a given area

• measured in atmosphere (atm) and the SI unit of pressure = pascal (Pa)

Pounds per square inch measures what?

Measures pressure as the force applied to an area of 1 square inch (psi)

Ideal Gas

A gas that perfectly adheres to the kinetic molecular theory of gases is said to be this

Kinetic Molecular Theory of Gases

• Gas particles are far apart from each other

• Gas particles are in constant, random motion, the particle have a range of speed

• Gas particles have no attractive forces btw. them; when collided energy is conserved

• Gas particles are moving and therefore have kinetic energy

Boyle’s Law

The volume of a fixed amount of gas at constant temp. is inversely proportional to the pressure.

• increase in pressure on a gas will result in a decrease of its volume

Charles’s Law

An increase in the temp. of the gas will result in an increase in its volume, and vice versa

Gay Lussac’s Law

When temp. increases so does pressure

The Combined Gas Law

Pressure, volume, and temp. hold the same relationship, even if all three change for the same amount of gas

Freezing and Melting

Between liquids and solids

Vaporization and Condensation

Between liquids and gases

Sublimation and Deposition

Between solids and gases

• sublimation: solid → gas

• deposition: gas → solid

Physical Equilibrium

The movement of the molecules btw. the vapor and liquid phase and vice versa happens at a constant rate

Vapor Pressure

The pressure caused by the molecules pushing into the space above the liquid

• As temp. increase more molecules from the liquid gain enough energy to become a gas

• More molecules in the gas phase increases the vapor pressure

Boiling Point

When the molecules have enough energy to change from a liquid to a gas (vaporize)

Attractive Forces

Caused by the attraction of an electron-rich area of one compound to an electron-poor area of another compound

• if the attraction is between two molecules, it is called an intermolecular force

Types of Attractive Forces

1. London forces

2. Dipole-dipole

3. Hydrogen bonding

4. Ion dipole

5. Ionic Attraction

London Forces

Occur momentarily between all molecules when electrons become unevenly distributed over a molecule’s surface

• Occurs in all compound but these forces are significant only in the case of nonpolar molecules bc these are the only attractive forces present btw. nonpolar molecules

Dipole-Dipole Attraction

The attraction of a partially positive end of one molecule to the partially negative end of another molecule

• stronger than London forces

• Do not exist btw. nonpolar molecules

Hydrogen Bonding

Involves a polarized hydrogen and is much stronger than other diploe-dipole forces

• requires the interaction of two parts, a donor hydrogen and an acceptor pair of electrons

Ion-Dipole Attraction

Results from the attraction of an ion to the opposite partial charge on a polar molecule, stronger than hydrogen bonding

• ex.: salt (ionic) dissolving in water (polar)

Ionic Attraction

The strongest force because it involves more than just an uneven distribution of electrons.

• When negative anions attract positive cations

Golden Rule of Solubility

Like dissolves like

• Molecules that have similar polarity and participate in the same types of attractive forces will dissolve each other

Hydrophilic v. Hydrophobic

• Philic: water-loving

• Phobic: water-fearing

Amphipathic Compounds

Molecules like fatty acids that both polar and nonpolar parts

• not soluble in water because of the large nonpolar tails present

• amphipathic compounds like soaps are called emulsifiers because they allow nonpolar and polar compounds to be suspended in the same mixture

Steroids

Lipids with a structure that contains a four-membered fused ring called a steroid nucleus

• cannot be broken into smaller components through hydrolysis 

Solution

Consists of at least one substance → the solute evenly dispersed throughout a second substance → the solvent

Aqueous Solutions

A solution in which water is the solvent

Colloids

A homogenous mixture containing particles ranging from 1-1000 nm in diameter

• mixtures do not separate upon standing and are not transparent

Suspension

A mixture containing particles greater than 1000 nm in diameter

• separate upon standing

Crystalline Solutions

Solutions that contain small solutes that completely dissolve in aqueous solution

• ex: normal saline and 5% dextrose in water

Unsaturated Solution

When a solution does not contain the maximum amount of the solute that the solvent can hold

Saturated Solution

When a solution contains all the solute that can possibly dissolve; if more solute is added, the additional solute will remain undissolved

Gas Solubility and Temperature

The solubility of a gas dissolved in water decreases with a rise in temperature.

• In a soda can, the warmer it is the more gas moves into the space above the liquid → increasing pressure, and eventually the can will pop

Solubility and Temperature

The solubility of most solids dissolved in water increases with temperature

Solubility and Pressure (Henry’s Law)

The amount of a gas that can dissolve in a liquid increases as the pressure of the gas in the space above the liquid increases

Electrolytes

Solutes that produce ions in solution

Strong Electrolytes

Ionic compounds that dissolve in water

Nonelectrolytes

Soluble covalent compounds that do not conduct electricity; dissolve in water but do not ionize in water

• In reactions nothing changes they only change from (s) → (aq)

Weak Electrolytes

Can partially ionize in water, and contain a highly polar bond that can dissociate, forming some ions in water

• weakly conduct electricity

• use reversible arrow in reactions

Concentration

The amount of each ingredient dissolved in the liquid determines this

• amount of solute/amount of solution (total amount)

Dilution

When the amount of solute stays the same, but the volume of solution increases; as a consequence, the concentration of the solution decreases

• C_initial x V_initial = C_final x V_final

Isotonic Solutions

A solution outside of a cell having the same concentration of solutes as the solution on the inside of the cell

Hypotonic Solution

A solution outside of a cell having a lower concentration of solutes than the solution inside the cell 

Osmosis

The passage of water through a semipermeable membrane

Osmotic Pressure

The pressure that water exerts during osmosis. This amount of pressure applied to the more concentrated solution of the two separated solutions would stop osmosis

Hypertonic

A solution outside the cell having a higher concentration of solutes than the solution inside the cell → dehydration

Physiological Solutions

A solution that is isotonic with normal body fluids