Chemical to Electrical Energy:
A device which converts chemical energy into electrical energy is called a cell, or battery (a collection of cells). It consists of a pair of dissimilar metals in an electrolyte. The more reactive metal dissolves and turns into ions, thereby producing electrons. These electrons then travel to the less reactive metal electrode, and bubbles of hydrogen are produced at this electrode.
This production or movement of electrons is electricity, so electrical energy has been generated and the bulb that completes the circuit and is connected to the electrodes lights up.
How bright the bulb is depends on the difference in the reactivities of the two metals. If the metals are far apart in the reactivity series, the bulb is bright, but does not stay alight for a very long time. If the metals are closer in the reactivity series, the bulb is less bright, but stays alighted for a longer time.
If the electrolyte in the cells is a paste, as opposed to a liquid, it is called a dry cell. These are the sort of cells most commonly found in the home. They are a convenient, portable energy source and are reasonably cheap to buy.