Quality versus quantity of energy

Note that if we reverse the second reaction (which means we must change the sign of AH) and sum the two reactions, we obtain the desired reaction  

Thus 2 kJ of energy is required to change 1 mole of graphite to diamond. This process is endothermic. 

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Which energy is easier to use to do work the concentrated energy in the gasoline or the thermal energy spread from Chicago to Denver Of course, the energy concentrated in the gasoline is more convenient to use. 

This example illustrates a very important general principle when we utilize energy to do work, we degrade its usefulness. In other words, when we use energy the quality of that energy (its ease of use) is lowered. 

In other words, when we use energy the quality of that energy (its ease of use) is lowered. 

You may have heard someone mention the heat death of the universe. Eventually (many eons from now), all energy will be spread evenly throughout the universe and everything will be at the same temperature. At this point it will no longer be possible to do any work. The universe will be dead.  

Greenhouse effect Energy spread Matter spread Entropy 

Fuel that consists of carbon-based molecules derived from the decomposition of once-living organisms 

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