What happens when a metal bar is heated? A The distance between the molecules increases, making the bar longer.
B The molecules get larger, making the bar longer.
с The molecules vibrate more quickly, making the bar denser.
D The speed of the molecules increases, making the bar thinner.

When something is heated, its atoms vibrate. If one end of a metal bar is heated, the atoms at that end vibrate more than the atoms at the cold end. The vibration spreads along the bar from atom to atom. ... Metals are good conductors of heat.

Explanation:

some think that theories become laws, but theories and laws have separate and distinct roles in the scientific method. a law is a description of an observed phenomenon in the natural world that hold true every time it is tested. it doesn't explain why something is true; it just states that it is true.