Which type of energy is likely changed into thermal energy in this hand warmer?

The question seems to be incomplete as it does not specify the type of hand warmer. However, in most cases, hand warmers work by a chemical reaction which is a form of chemical energy. So, the chemical energy in the hand warmer is likely changed into thermal energy.

Here are the steps:

1. The hand warmer is activated, usually by shaking or squeezing it. This starts the chemical reaction.
2. The chemical reaction produces an exothermic reaction, meaning it releases heat.
3. The heat (thermal energy) is then transferred to your hand when you hold the hand warmer.
4. The hand warmer continues to produce heat until the chemical reaction is complete.

So, in conclusion, the type of energy that is likely changed into thermal energy in a hand warmer is chemical energy.