Final answer:
Small amounts of free water can be introduced in empty or partially filled fuel cells/tanks through differences in thermal expansion, by-product of fuel cell reactions, or through the process of electrolysis.
Step-by-step explanation:
Small amounts of free water can be introduced in empty or partially filled fuel cells/tanks through various means.
- Differences in thermal expansion of materials can cause gasoline to overflow from a freshly filled tank on a hot day.
- Fuel cells that generate electricity from hydrogen and oxygen can produce water as a by-product.
- Electrolysis, a process that drives the decomposition of water using an external voltage, can also introduce small amounts of free water.