Absolutely EVERYTHING you need to know about energy and much much more!
Hannah's Energetics Emporium
Entropy? Enthalpy? more like gibberish!?!! Don't worry you have come to the right place!
Key Terms
Endothermic
(of a reaction or process) accompanied by or requiring the absorption of heat
ΔH is positive (overall change is positive)
(Figure A)
Specific Heat Capacity
the heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree).
Thermochemistry
Thermochemistry is the study of heat changes that occur during chemcial reactions.
Entropy
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In thermodynamics, entropy (usual symbol S) is a measure of the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder.
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red light shows energy being RELEASED
Fig A Bond making is Exothermic
Entropy Change
ΔS
Change in disorder of a system is known as ΔS, entropy change. More disordered a system becomes, ΔS will become more positive. More ordered systems will have negative ΔS values.
Exothermic
(of a reaction or process) accompanied by the release of heat.
ΔH is negative (overall change is negative)
(Figure B)
Temperature
the degree or intensity of heat present in a substance or object, especially as expressed according to a comparative scale and shown by a thermometer or perceived by touch.
It is NOT the same
as HEAT
Specific Heat Capacity Equation
Q = MC Δ T
Bond Enthalpy
The amount of energy required to break 1 mol of bonds in gaseous covalent molecules under standards conditions.
The bond enthalpy reflects the strength of the bond. If a bond requires a great amount of energy to be broken, that means that the bond is very strong compared to a bond that requires less energy.
Calorimeter
an apparatus for measuring the amount of heat involved in a chemical reaction or other process (fig C)
The change in enthalpy is defined as the heat transferred by a closed system during a chemical commonly used when describing the thermodynamics of a reaction. The unit of entahlpy change Δ H is kJ
ΔH change in enthalpy
bLUE LIGHT = energy released
Fig A Bond Breaking is Endothermic
Symbol For Entropy
ΔS
Born Haber Defintion
The term "Born Haber Cycles" refer to energy cycles which are drawn out to show the steps involved for the formation of ionic compounds.
Hess's Law Main Rule
Hess's Law of Constant Heat Summation (or just Hess's Law) states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes. This law is a manifestation that enthalpy is a state function. (chemwiki)
Standard Enthalpy of Combustion delta Hc
The enthalpy change when one mole of a substance is completley combusted in oxygen under standard conditions (298 K and 100 kPa Pressure.
Law of Conservation of Energy
The Enthalpy change of a reaction is dependent on the difference between the enthalpy of the products and the enthalpy of the reactants.
Enthalpy Change of a reaction is the same despite the route which is taken. It can go directly to the product or through an intermediate
This law refers to the law of conservation of energy.
Law of enthalpy of combustion can be used to find out enthalpy changes that can't be measured directly.
Intermediates
The Intermediates refer to the components in the reaction which are halfway between reactants and being converted into the products.
Standard Enthalpy of Formation delta Hf
Enthalpy change when one mole of the compound is formed in its elements in their standard states at 298 K and 100 kPa Pressure. Following this, delta Hf for an element in its standard state will be zero.
