NSES Content Standard B Physical Science: Light, heat, electricity, and magnetism  Grades K-4, page 127  Heat can be produced in many ways such as burning, rubbing, and mixing one substance with another. Heat can move from one object to another by conduction.

 
Benchmark 4E The Physical Setting: Energy Transformations
Grades 3-5, page 84
Things that give off light often also give off heat. Heat is produced by mechanical and electrical machines, and any time one thing rubs against something else.

Benchmark 4E The Physical Setting: Energy Transformations
Grades 3-5, page 84
When warmer things are put with cooler ones, the warm ones lose heat and the cool ones gain it until they are all at the same temperature. A warmer object can warm a cooler one by contact or at a distance.