measure of the average speed of molecules Celsius = Kelvin-273 Kelvin = Celsius+273

*Celsius and Kelvin are not the same values, but they have the same increments

Factors Which Affect Phase Change

1.Temperature

2.Pressure

1.an increase in temperature causes the molecules to move faster. Solid to liquid to gas Decrease in temperature causes the molecules to slow down. Gas to liquid to solid

2.The more pressure a liquid is under, the harder it is for that substance to become a gas. i.e.)slightly increasing the pressure by putting a lid on top of a pot of boiling water. The liquid condenses on the top before falling back as a liquid

For a reaction to occur, particles must collide with an effective collision(proper angle - must have a positive and negative to create a bond, and sufficient energy)

1.Nature of reactants -how reactive are the substances? (will it be a fast or slow reaction? i.e.copper and water reacts slowly during oxidation) -Are the reactants even able to react? (i.e.Gold doesn't react with water)

2.Concentration - the amount of substance -high concentration of reactants = higher reaction(rxn) rate -low concentration of reactants = lower rxn rate

3.Temperature -increase in temp. = higher rxn rate (due to faster moving molecules and thus more collisions) -decrease in temp. = lower rxn rate 4.Presence of a Catalyst - substance that speeds up a chemical reaction without changing the outcome of the reaction

chart which shows progression of energy during a reaction.

Activation energy is the amount of energy required to start a chemical reaction

Heat of reaction(ΔH_r) is the heat gained or lost during chemical reaction

1.Endothermic Reaction

2.Exothermic Reaction

1.heat is absorbed - it is gained. Energy of reaction(ΔH_r) is positive

2.heat is released - it is lost. Energy of reaction(ΔH_r)is negative.

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Can produce "product" or may reverse to produce "reactant"

Lowers the activation energy needed to produce products

force per unit area(caused by atoms or molecules hitting walls of container)

Factors affecting pressure are: -number of molecules or mass(# of collisions)

-volume of the container(# of collisions)

-temperature (speed with which atoms hit container walls)

the "Gas Laws" describe the behavior of gases under various conditions of temperature, pressure and volume

P₁V₁ = P₂V₂

The pressure exerted by a gas varies inversely(opposite:increase of volume, decrease in temp., and vice versa) with the volume(if the number of atoms and the temperature remain constant)

V₁/T₁ = V₂/T₂

The pressure of a gas varies directly(same:temp. increases, pressure also increases) with the temperature(in Kelvin)(if the number of molecules and the volume remain constant)

V₁/T₁ = V₂/T₂

The volume of a gas varies directly with the temperature(in Kelvin)(if the number of molecules and the pressure remain constant)

P₁V₁/T₁ = P₂V₂/T₂

incorporates Boyle's, Charles' and Gay Lussac's Laws into one mathematical formula

Pressure: P (atm, mmHg, torr, or KPa)

Volume: V (L or mL)

Temperature: T (Kelvin)

PV = nRT

Describes the behavoir of an "ideal gas"(no attraction between molecules)

Ideal gas- an imaginary gas that perfectly fits all assumptions of the Kinetic-molecular theroy

P= pressure (any unit)

V= volume (liters)

n = number of moles (moles)

R= gas "constant"

T= temperature (K)

Example 1)What pressure is exerted by 4.50 moles of gas in a 198 liter container at 8.0°C?

PV = nRT...

crpss out like units...P(198L) = 4.50mol(.0821(Latm/molK)(281K)...

198P = 103.815atm...divide by 198 on both sides

Answer: P= .52atm

Ex.2) What is the volume occupied by 9.45 grams if C₂H₂ at STP?

...convert the mass of C₂H₂ into moles: 9.45gC₂H₂ x (1mol/26gC₂H₂)= .363moles

PV = nRT

(1atm)V = .363mol(.0821Latm/molK)(273K)

V= 8.13atm

In a mixture of gases, the total pressure of the mixture is equal to the sum of the pressures that each gas would exert by itself in the same volume

P_total = P₁+P₂...+P_n

Example)What is the atomospheric pressure if the partial pressure of N2, O2, and Ar are 604.5mmHg, 162.8mmHg, and 0.5mmHg respectively?

604.5 + 162.8 + 0.5 = 767.8mmHg!

Ex.1) A gas occupies 25.0mL at 17.0ºC. If the volume is decreased to a 12.0ml, find the new temperature in degrees Celsius. Assume constant pressure.

V₁/T₁ = V₂/T₂

17.0 + 273 = 290K (convert ºC to Kelvin)

...25mL/290K = 12.0ml/T₂...cross multiply

...T₂(25mL) = (12.0ml)(290K)...divide each side by 25mL to get T₂ by itself

T₂= (12.0)(290K)/25 = 139.2K...convert back to Celsius

139.2 - 273 = -133.2...use sig figs

Answer = 130ºC