States of Matter and Intermolecular Forces (Slide Deck 2)

Properties are determined by the _____________ of molecules and the forces acting between them

Molecules

Have a fixed shape and volume because their molecules are tightly packed in an ordered lattice

Solids

Have a high density and are nearly incompressible

Solids

In solids, molecules _________ around fixed positions but do not move freely

Vibrate

Some solids with ________ vapor pressures, such as iodine and camphor, can transition directly from solid to gas without melting

High

Transition directly from solid to gas

Sublimation

Transition directly from gas to solid

Deposition

These have a definite volume but take the shape of their container

Liquids

These are denser than gases but less dense than solids

Liquids

Molecules are less tightly bound than in solids, allowing them to move past each other (flow) and diffuse)

Liquids

Have neither fixed shape nor fixed volume; they expand to fill any available space

Gases

Molecules move rapidly and randomly, with weak forces between them

Gases

Gases are highly ____________ and generally invisible

Compressible

Matter can change between states by gaining or losing _________

Energy

Transition from solid to liquid

Melting

Transition from liquid to gas

Vaporization

Transition from gas to liquid

Condensation

Transition from solid to gas

Sublimation

Transition from gas to solid

Deposition

Some structures exhibit a __________, which has properties in between other phases

Mesophase

Behave like liquids in flow but have some molecular order like solids

Liquid crystals

Occur above a substance’s critical temperature and pressure, where liquid and gas phases are indistinguishable; behave like a gas and a liquid

Supercritical fluid

Supercritical fluid extraction uses a supercritical fluid - a substance above its _________ temperature and pressure - where it exhibits properties of both a gas and a liquid

Critical

Extraction vessel filled with CO2 and brought above critical temp/pressure; supercritical CO2 passes through the solid or liquid sample, dissolving target compounds; extract-laden CO2 is depressurized in a separator, causing the solute to precipitate out; CO2 can be recycled, reducing waste and cost

Supercritical fluid extraction

The specific temperature and pressure where multiple phases coexist

Critical point

Attractions or repulsions between molecules

Intermolecular forces

Molecule-molecule of the same substance; responsible for surface tension and melting/boiling points of solids/liquids

Cohesive forces

Molecule-molecule of different substances; responsible for capillary action (drug movement through membranes, wicking in dosage forms); drug excipient interactions in formulations

Adhesive forces

Prevent collapse of molecules when too close; keeps molecular structure stable; important in protein folding, membrane stability, and drug-protein binding

Repulsive forces

Intermolecular interactions can be visualized with a __________ _______ diagram (energy vs. distance between nucleus)

Potential energy

When molecules are far apart, there is _____ attraction and high potential energy

Weak

When particles move closer, attraction increases and potential energy __________

Decreases

Minimum energy point on potential energy diagram; most stable state

Collision diameter

When atoms move too close, electron clouds overlap and there is strong __________

Repulsion

Attractive forces act over _________ distances than repulsion

Longer

Attractive forces are inversely proportional to ________ distance

Separation

Short-range, rise very rapidly with decreasing distance

Repulsive forces

Repulsive forces approximate ____________ dependence

Exponential

Molecules prefer a _______ point where attraction=repulsion; determines molecular packing in solids and stability of liquids

Balance

Collectively describe weak electrostatic interactions between molecules

Van der Waals

Van der Waals energies are low, but __________ effects are crucial in drug formulation and binding

Additive

Occur between polar molecules with permanent dipoles; strength is 1-7 kcal/mol

Dipole-dipole

Name for dipole-dipole forces

Keesom forces

Example is binding of drug with carbonyl group to polar amino acid side chains in receptors

Dipole-dipole

A polar molecule induces a dipole in a nearby nonpolar molecule; strength is 1-3 kcal/mol

Dipole-induced dipole

Name for dipole-induced dipole

Debye forces

Strength of dipole-dipole

1-7 kcal/mol

Strength of dipole-induced dipole

1-3 kcal/mol

Arise from temporary fluctuations in electron distribution in nonpolar molecules

London dispersion forces

Strength for london dispersion forces

0.5 - 1 kcal/mol

Important for nonpolar drug molecules and hydrophobic interactions in drug-receptor binding

London dispersion forces

Occurs between a charged ion and a polar molecule; strength is 1-7 kcal/mol

Ion-dipole

Strength for ion-dipole

1-7 kcal/mol

Ion distorts the electron cloud of a nonpolar molecule; important for drug solubility, enhancers, and lipid-ion interactions

Ion-induced dipole

A strong type of dipole-dipole interaction; occurs when hydrogen is covalently bonded to a highly electronegative atom (O, N, F) and interacts with another electronegative atom

Hydrogen bonding

Between molecules

Intermolecular

Within the same molecule

Intramolecular

Strength of hyrogen bond

5-10 kcal/mol

Hydrogen bonds can be ________ covalent in character (electron delocalization)

Partially

Critical in protein folding, drug-receptor binding specificity, and physical properties of drugs

Hydrogen bonding

Drugs with lots of this have higher boiling/melting points and increased solubility in water (important for formulation)

Hydrogen bonding

Drug _________ depends heavily on whether the drug can form hydrogen bonds and dipole interactions with water

Solubility

Drug __________ in solid and liquid formulations is governed by a balance of cohesive and adhesive forces

Stability

Gas molecules move very quickly due to their high ________ _______

Kinetic energy

Gases mix easily and inhaled drugs act _________

Rapidly

These have little attraction between molecules and do not “stick” together; important for drug delivery via inhalation since molecules spread out uniformly

Gases

These expand to fill the entire space of their container

Gases

Gases can be __________ significantly because of the large empty spaces between molecules; used in packaging drugs (e.g., metered-dose inhalers) and in supercritical fluid extraction

Compressed

Typically invisible

Gases

Gas molecules move randomly and _______ with each other

Collide

Collision of gas with walls of container generates _____ ________

Gas pressure

Gases occupy space, even though their _________ is low

Density

All gas laws (Boyle’s law, Charles’s law, Ideal gas law) require temperature in __________

Kelvin

When calculating gas solubility, vapor pressure, or pressure inside containers, __________ must be used

Kelvin

Gases and vapors are used in ____________ therapy (e.g., anesthetics, bronchodilators)

Inhalation

Gas solubility and __________ must be understood when designing aerosols, sprays, and foams

Compressibility

PV = nRT

Ideal Gas Law

Results from collisions of gas molecules with container walls

Pressure

Space occupied by the gas

Volume

Number of gas particles

n

Average kinetic energy of gas molecules (must be in Kelvin)

Temperature

0.0082 Latm/molK

Gas constant

Explains gas behavior in sterilization (autoclaves), storage (pressurized containers), and inhalation therapies (aerosols, anesthetics)

Ideal Gas Law

An assumption of the ideal gas model is that molecules have no ___________ interactions (no attraction/repulsion)

Intermolecular

Assumption of ideal gas molecule is collisions between molecules and container walls are __________ ________

Perfectly elastic

An assumption of the ideal gas model is that gas molecules are _______ __________ with negligble volume

Point masses

Real gases __________, especially at high pressure or low temperature

Deviate

At constant temperature for a fixed amount of gas, the product of pressure and volume is constant

Boyle’s Law

Boyle’s law says that gas pressure is _________ proportional to volume

Inversely

If volume of a gas decreases, pressure _________

Increases

If volume of a gas increases, pressure __________

Decreases

At constant pressure for a fixed amount of gas, volume is proportional to temperature

Charles’s law

At constant pressure for a fixed amount of gas, volume is proportional to __________

Temperature

Volume increases for a gas as __________ increases

Temperature

Says that the product of pressure and volume divided by temperature is a constant

Combined gas law

Derived from standard conditions; 1 mole at 1 atm and 273 K

Gas constant

The ideal gas law can be rearranged to determine the ________ ________ of a gas

Molecular weight

Equation for number of moles

n = g/M

Primarily refer to oxygen and carbon dioxide

Blood gases

Essential for cellular metabolism and energy production

Oxygen