Which of the following best describes internal energy? a. the difference between the kinetic and potential energies of the particles in a system b. the sum of the kinetic and potential energies of the particles in a system c. the sum of the kinetic and thermal energies of the particles in a system d. the difference between the kinetic and thermal energies of the particles in a system

Batteries convert chemical energy into electrical energy. It is able to store electrical energy in the form of chemical energy. 
Have you ever seen the two different sides of a battery? One side is often labelled with a positive sign, and the other with a negative sign. Inside the battery are four cells where two processes take place. One process uses electrons, and the other creates electrons. When the electrons flow, it creates electricity. 
Drums convert mechanical energy into sound energy. 
When a musician bangs his/her drumstick on the drum, the motion makes a sound. This movement turned motion into sound.