Final answer:
Common fuel gases for blowtorches include propane and butane for standard uses, and acetylene and oxygen for high-temperature applications such as welding.
Step-by-step explanation:
The most common fuel gases used in blowtorches are propane and butane for standard applications, while acetylene and oxygen are used in high-temperature applications such as welding. Propane, with the chemical formula C3H8, is a hydrocarbon that combusts with oxygen to produce carbon dioxide and water vapor, releasing heat. This reaction is balanced as C3H8 + 5O₂ → 3CO₂ + 4H₂O. Butane (C4H₁₀), another hydrocarbon, behaves similarly and combusts to form carbon dioxide and water vapor. In high-temperature applications, compressed acetylene is mixed with oxygen to achieve the intense heat required for welding metals. Methane (CH4) and ethane are other examples of hydrocarbons used in some fuel applications, but they are not as commonly used in blowtorches.