heat
Heat comes from many sources like:
1. Sun
2. Fire
Things in the sunshine are warmer than things in the shade:
3. Friction
(when one object moves against another)
Rub your hands together for 30 seconds, then place your palms on your cheeks. The heat you feel is the result of a mechanical force called friction.
4. Electrical
heaters
stove burner
5. Chemical
oil
wood
kerosene
6. Nuclear
