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Laboratory

ThermodynamicsThermodynamics

“Thermodynamics is a funny subject. The first time you go through it, you don't understand it at all. The second time you go through it, you think you understand it, except for one or two small points. The third time you go through it, you know you don't understand it, but by that time you are so used to it, it doesn't bother you anymore.”

Arnold Sommerfeld, German theoretical physicist

What is What is Thermochemistry?Thermochemistry?

(aside from being (aside from being loads of funloads of fun, of course!), of course!)

Thermochemistry is the study of the relationship of heat and chemical reactions

Can tell us Whether a reaction will occur What drives a reaction In complex, systems, we can use

thermochemistry in combination with structural information to help elucidate mechanisms

The wonderful things you The wonderful things you can do with can do with

Thermochemistry Thermochemistry oror

How aminoglycoside How aminoglycoside antibiotics kill bacteriaantibiotics kill bacteria

Studying small changes in the heat absorbed or evolved by the system can tell us how this works

DNA RNA (bacteria use different

“machinery”)

Protein

/

Aminoglycoside-rRNA BindingAminoglycoside-rRNA Binding

Energy and Chemical ReactivityEnergy and Chemical Reactivity

Types of EnergyTypes of Energy

The First Law of The First Law of ThermodynamicsThermodynamics

Conservation of Energy= Energy is neither created nor destroyed

This means that Euniverse = 0

During a chemical or physical change, energy will be transformed from one type to another

Energy InterconversionEnergy Interconversion

Wind moves turbine

Turbine produces electricity

Electricity is used to lyse water into H2

and O2

H2 is stored and then burned

J kJ cal kcal BTU kWh

1 J = 1 0.001 0.2390 2.390 x 10-4 1055 2.778 x 10-7

1 kJ = 1000 1 239.0 0.2390 1.0557 2.778 x 10-4

1 cal = 4.184 4.184 x 10-3 1 0.001 252 1.162 x 10-6

1 kcal = 4184 4.184 1000 1 0.252 1.162 x 10-3

1 kWh = 3.6 x 106 3.6 x 103 8.604 x 105 860.4 2.93 x 10-4 1

Energy UnitsEnergy Units

Read as 1J = 0.2390 cal

Temperature and HeatTemperature and Heat

Heat (q) and Temperature (T) are not the same!

The more thermal energy something has, the greater the motion of its atoms

The total thermal energy in an object is the sum of the individual energies of all the atoms, molecules, or ions

What happens to thermal (heat) What happens to thermal (heat) energy?energy?

Warms another object (transfer)

Causes a change of state

Is used in an endothermic reaction

Which statement below best describes the Which statement below best describes the process of placing a thermometer initially at process of placing a thermometer initially at

22ºC into ice water?22ºC into ice water?

1 2 3 4

25% 25%25%25%1. Some of the thermal energy of

the ice water is transferred to the thermometer.

2. Some of the thermal energy of the thermometer is transferred to the ice water, melting some of the ice.

3. The atoms of mercury begin to move faster as a result of the thermal energy transfer between the thermometer and the ice water.

4. The mercury in the thermometer begins to expand as a result of the thermal energy transferred.

Heat TransferHeat Transfer

If heat (q) is transferred, in which direction does it go? From hotter to cooler (related to the 2nd Law,

but we’ll get to that later) Heat lost = Heat gained (1st Law)

qwarmer = -qcooler

Thermal equilibrium= when two objects in contact reach the same temperature

System and SurroundingsSystem and Surroundings

System = The thing under study Surroundings = Everything else in the

universe Energy transfer between system and

surroundings Exothermic- system gives off heat Endothermic- system takes in heat

Heat TransferHeat Transfer

When I heat an object, how much energy will it require? It depends . . .1. Quantity (How much stuff do I have?)

2. Size of the temperature change

3. Identity of the material

TmCq