Chemistry Exam 3

Define compressibility:

A measure of the change in volume of a sample of matter resulting from a change in pressure

Define thermal expansion:

A measure of the change in volume of a sample of matter resulting from a change in temperature

Define kinetic energy:

Energy that matter possesses because particles are in motion

Define potential energy:

Stored energy that matter possesses as a result of its position, condition, and/or composition

Potential energy is dependent on the ________ that result from the position of the particle relative to other particles.

Electrostatic interactions

Define electrostatic interaction

An attraction or repulsion that occurs between charged particles

The five statements of kinetic molecular theory explain what?

The physical behavior of matter

An assumption is that any particle is in motion unless at absolute 0

What is Statement 1 of kinetic molecular theory?

Matter is ultimately composed of tiny particles that have definite and characteristic sizes that do not change

What is Statement 2 of kinetic molecular theory?

The particles are in constant random motion and therefore possess kinetic energy

What is Statement 3 of kinetic molecular theory?

The particles interact with one another through attractions and repulsions and therefore possess potential energy

What is Statement 4 of kinetic molecular theory?

The kinetic energy (velocity) of the particles increases as the temperature is increased

What is Statement 5 of kinetic molecular theory?

The particles in a system transfer energy to each other through elastic collisons

Define elastic collisions:

Total kinetic energy remains constant

(no energy is lost)

Define inelastic collisions:

The energy of motion is lost

Kinetic energy is a ________ force because it causes particles to be moved away from each other.

Disruptive

Temperature dependent

Potential energy is a __________ force because it holds particles together.

Cohesive

Independent of temperature

What determines the physical state of a substance?

The dominant force that is dependent on the temperature

Define solid:

The physical state characterized by a large amount of potential energy (cohesive forces) relative to the amount of kinetic energy (disruptive forces)

Possess vibrational energy (kinetic energy)

The 4 properties of a solid:

Definite volume and shape

High density

Small compressibility

Very small thermal expansion

Define liquid:

The physical state characterized by potential energy (cohesive forces) and kinetic energy (disruptive forces) of about the same magnitude

The 4 properties of a liquid:

Definite volume and indefinite shape

High density

Small compressibility

Small thermal expansion

Define gas:

The physical state characterized by a complete dominance of kinetic energy over potential energy

4 properties of a gas:

Indefinite volume and shape

Low density

Large compressibility

Moderate thermal expansion

Define gas law:

A generalization that describes in mathematical terms the relationships among the 4 variables of a gas

Define pressure:

The force applied per unit area on an object

Define Boyle’s Law:

States that the volume of a fixed amount of a gas is inversely proportional to the pressure applied to the gas if the temperature is kept constant

P1V1 = P2V2

Define Charles’s Law:

States that the volume of a fixed amount of gas is directly proportional to its Kelvin temperature is the pressure is kept constant

V1/T1 = V2/T2

Define combined gas law:

States that the product of the pressure and volume of a fixed amount of gas is directly proportional to its Kelvin temperature

P1V1/T1 = P2V2/T2

Define ideal gas law:

Gives the relationships among the 4 variables temperature, pressure, volume, and molar amount for a gaseous substance at a given set of conditions

PV=nRT

Standard temperature is ______ degrees Celsius and standard pressure is ____ atm.

0

1

One mole of any gas at STP will occupy _____.

22.4L

Dalton’s law of partial pressures:

States that the total pressure exerted by a gas mixture is the sum of the partial pressures of the individual gases present

Ptotal = Pa + Pb + Pc + …

Define partial pressure:

The pressure that a gas in a mixture of gases would exert if it were present along under the same conditions

Partial pressure of a gas will ALWAYS be less than the total pressure of the gas

Percent composition:

The ratio of the amount of the individual gas to the total amount of the gas mixture expressed as a percentage (multiplied by 100)

Percent comp. = amount of gas/total amount of gas mixture x 100

Change of state:

A process in which a substance is transformed form one physical state to another physical state

Endothermic

Heat energy is reabsorbed

Evaporation

Melting

Sublimation

Exothermic:

Heat energy is given off

Condensation

Freezing

Sublimation

Evaporation

The process by which molecules change from the liquid phase to the gas phase

Factors effecting the rate of evaporation:

Surface Area

Temp. of liquid

Evaporation affects a liquid in 2 ways:

The amount of liquid decreases

The temp. of the liquid decreases

Vapor:

A gas that exists at a temp. and pressure that would normally exist as a solid or liquid

Open system:

A system where there are constant changes in the amount of matter and energy

The number of molecules of a substance does not remain constant

Heat is gained or lost

Closed system:

A system where the amount of matter and energy remains constant (regardless of its state)

Molecules cannot enter or leave the system

Heat is not lost or gained

In a closed system, how does water vapor react in a fixed space?

They are trapped

Evaporation in a closed system:

Two processes occur simultaneously:

Evaporation and condensation

Physical equilibrium:

A state in which two opposing physical processes take place at the same rate

The rate of evaporation is the same as the rate of condensation

Called a dynamic equilibrium because the forward and reverse processes still occur at the molecular level

Steady-state system:

No visible changes at the macroscopic level

Physical equilibrium:

A state in which two opposing physical processes take place at the same rate

The rate of evaporation is _______ as the rate of condensation in physical equilibrium.

The same

Vapor pressure:

The pressure exerted by a vapor above a liquid when the liquid and vapor are in physical equilibrium with each other

Boiling:

A form of evaporation (liquid to vapor) that occurs within the body of the liquid through bubble formation

This occurs when the vapor pressure of the liquid equals the external pressure:

Boiling

In boiling, open container - external pressure is __________.

Atmospheric pressure

In boiling, closed container - external pressure _________

Can be varied

The boiling point:

The temperature at which the vapor pressure of the liquid equals the external pressure or atmospheric pressure

In boiling point, an increase in the ____________ causes an ________ in the boiling point.

External pressure

Increase

In boiling point, a ________ in the external pressure causes a ____________ in the boiling point.

Decrease

Decrease

The normal boiling point is:

The temperature at which a liquid boils at 760 mmHg or 1 atm

Substances with low vapor pressures have ___________ temperature boiling points.

High

Substances with high vapor pressures have __________ temperature boiling points.

Low

Intermolecular forces:

The attractive force that act between a molecule and another molecule

Intermolecular forces are electrostatic in nature meaning …

Positive - negative attraction

Three types of intermolecular forces:

Dipole-Dipole

Hydrogen bonds

London forces

Dipole-dipole interactions:

An intermolecular forces that occurs between polar molecules

Polar molecules have a constant ______ and _____ region.

Positive, negative

The greater the polarity of the molecule, the ________ the strength of the dipole-dipole interaction.

Greater

The greater the strength of the dipole-dipole interaction, the __________ the boiling point of a liquid

Higher

Hydrogen bond

An extra-strong dipole-dipole interaction between a hydrogen atom covalently bonded to small, very electronegative atom and a lone pair of electrons on another small, very electronegative atom associated with another molecule

Hydrogen bonds can occur between _________ molecules or between _______ molecules.

Identical

Different

As molecular weight increases, the boiling point _________.

Increases

Density increases as water gets closer to _______.

Its freezing point

London dispersion forces

A weak temporary interaction that occurs between an atom or molecule (polar or nonpolar) and another atom or molecule (polar or nonpolar) due to the formation of an instantaneous dipole

This is the weakest of all intermolecular forces:

London dispersion forces

This occurs in all molecules, and the only intermolecular force found in nonpolar molecules:

London dispersion forces

This is also called van der Waals forces:

London Dispersion forces

An instantaneous dipole causes what?

An induced dipole in adjacent molecules

Instantaneous dipole:

Temporary uneven electron distribution

London forces are _________ and result in a net attraction of considerable strength.

Cumulative

London forces are _______ on the polarizability of the electrons.

Dependent

London forces influences what?

Physical properties

The boiling point is dependent on the type of ___________.

Intermolecular forces

Boiling points increase with _________ molecular mass.

Increasing

Boiling points of substances with similar molecular mass __________ as the polarity of the molecule increases.

Increases

Solution:

Homogenous mixture composed of two or more substances of each substance retaining its own chemical identity

Solvent

The component of a solution that is present in the greatest amount

The medium in which other substances are dissolved in

Solute

A component of a solution that is present in a lesser amount relative to that of the solvent

Solubility:

The maximum amount of specific solute that will dissolve in a given amount of a specific solvent under a given set of conditions

Factors that affect the solubility of a solute:

Nature of the solvent itself

Temp.

Pressure

Presence of other solutes

Solubility of a solid in a liquid:

Increases with increasing temperature

Solubility of gases in liquids:

Decreases with increasing temperature

Pressure only affects the solubility of ______:

Gases

Henry’s law:

States that the amount gas that will dissolve in a liquid at a given temp. is directly proportional to the partial pressure of the gas above the liquid

The solubility of a gas __________ with an _______ in pressure.

Increases

Increase

The solubility of a gas ______ with a _______ in pressure.

Decrease

Decrease

Saturated solution:

A solution that contains the maximum amount of solute that can dissolved under the conditions at which the solution exists

Supersaturated solution:

An unstable solution that temporarily contains more dissolved solute than that present in a saturated solution

Unsaturated solution:

A solution that contains less than the maximum amount of solute that can be dissolved under the conditions at which the solution exists

Concentrated solution:

A solution that contains a large amount of solute relative to the amount that could dissolve

Dilute solution

A solution that contains a small amount of solute relative to the amount that could dissolve

Aqueous solution:

Solution in which water is the solvent