Фильтры aqa triniti

фильтры aqa triniti

Transcript of Ch 9

Thermochemistry: Chemical Energy
Ch 9
Thermodynamics - science of heat and work and the фильтры aqa triniti from one form to another

Energy (E) - is the ability or capacity to do work or supply heat

Work (w) - is the energy required to move an object against a force

Heat (q) - фильтры aqa triniti amount of thermal energy transferred from one object to another object as a result of a temperature difference
Conservation of Energy
Forms of Energy
Kinetic Energy (Ek) - energy of motion
ex.

electrical energy (electrons allow charge movement)


Potential Energy (Ep) - energy of position; stored energy
ex.

фильтры aqa triniti

chemical bonds of molecules act as a storage medium
A diver:
Has Ep due to macroscale фильтры aqa triniti Ep to macroscale Ek.
Converts Ek,macro to Ek,nano (motion of water, heat).

First law of thermodynamics
"Law of Conservation of Energy"
Energy can neither be created nor destroyed
Energy can only фильтры aqa triniti from one form to another
The total energy of the universe is constant
Thermal Energy - the Ek of molecular motion and is measured by finding the temperature (T) of an object

Heat flows from hotter to cooler objects until they reach thermal equilibrium (have equal T ).

Consider a thermometer
As T фильтры aqa triniti Atoms move faster; on average get farther apart.


V of the material increases. Length of liquid column increases.

calorie (cal) - фильтры aqa triniti of фильтры aqa triniti necessary to raise the temperature of 1 gram of water by 1 degree Celsius.


system - part of universe under study

surroundings - everything else in the universe

universe = system + surroundings

Internal Energy (E) - energy within system; depends on temperature, type of material and amount of material.
If system is isolated from surroundings
- No energy transfer to surroundings
- Change in Energy = 0


If system is NOT isolated from surroundings
- Energy changes are measured from the point of view of the system.
Amount of Energy released/absorbed is proportional to the amount of reactants/products!
Does NOT depend on pathway!


Reversible
Overall change is zero if system returns to its original condition
Expansion work - work done as a result of volume change in the system ( 1 L atm = 101.3 J)


For example, the symbol for a standard enthalpy change is H°, read as "delta H standard" or, perhaps more commonly, as "delta H nought".
Enthalpy is a state function!
Calorimetry - experimental фильтры aqa triniti that allows energy change associated with a chemical or physical change to be determined
The larger the value = the more energy (heat) can be applied before фильтры aqa triniti temperature change occurs
Hess's Law

“If the equation for фильтры aqa triniti reaction is the sum of the equations
for two or more other reactions, then ΔH° for the 1st reaction must be the sum of the ΔH° values of the other reactions.”

Reactants and products in the individual steps are added and subtracted like algebraic quantities in determining the overall equation and reaction enthalpy.
Standard Enthalpy (Heat) of Formation

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