premise: a flashlight emits light sent2: a kind of is similar to a form of sent3: a flashlight is a kind of battery-operated device sent4: electrical devices convert from electrical energy  into other forms of energy sent5: batteries convert chemical energy to electrical energy sent6: battery is the source of electrical energy for battery-operated device sent7: a flashlight is a kind of electrical device sent8: light is a kind of energy.
hypothesis: when a flashlight is used, the energy is changed from chemical energy into electrical energy and then into light energy