Four balls have the same temperature. Which ball has the most thermal

energy?

The ball with the largest mass and highest specific heat capacity.

Explanation:

This is because, the thermal energy which is Q = mcΔT and since c = specific heat capacity of the ball, m = mass of ball and ΔT = temperature change = constant,

Q ∝ mc

So the thermal energy is directly proportional to mass and specific heat capacity of the ball, So, the ball with the highest product of these two properties has the highest thermal energy.