______________________________________ are good insulators.

When two objects are rubbed together they produce heat. This is called ____________________.

The biggest heat source for our planet is the ______________________.

___________________ like iron and copper are good conductors of heat.

____________________ are materials that allow heat to move easily through them and from one object to another through direct contact.

When ___________________________ is used, heat is produced.

_________________________ objects in a fire can produce heat.

Heat moves from ___________ to _______________.