Benchmark 4E
The Physical Setting: Energy Transformations
Grades 9-12, page 86

Transformations of energy usually produce some energy in the form of heat, which spreads around by radiation or conduction into cooler places. Although just as much total energy remains, its being spread out more evenly means less can be done with it.

NSES Content Standard B 
Physical Science: Conservation of energy and the increase in disorder 
Grades 9-12, page 180 
Everything tends to become less organized and less orderly over time. Thus, in all energy transfers, the overall effect is that energy is spread out uniformly. Examples are the transfer of energy from hotter to cooler objects by conduction, radiation, or convection and the warming of our surroundings when we burn fuels.