NSES Content Standard B 
Physical Science: Transfer of energy
Grades 5-8, page 155

In most chemical and nuclear reactions, energy is transferred into or out of a system. Heat, light, mechanical motion, or electricity might all be involved in such transfers.

Benchmark 4E The Physical Setting: Energy Transformations
Grades 6-8, page 85
Most of what goes on in the universe--from exploding stars and biological growth to the operation of machines and the motion of people--involves some form of energy being transformed into another. Energy in the form of heat is almost always one of the products of an energy transformation.

Benchmark 4E The Physical Setting: Energy Transformations
Grades 9-12, page 86
Different energy levels are associated with different configurations of atoms and molecules. Some changes of configuration require an input of energy whereas others release energy.

Benchmark 8C The Designed World: Energy Sources and Use
Grades 6-8, page 194
Energy can change from one form to another, although in the process some energy is always converted to heat. Some systems transform energy with less loss of heat than others.