[ Momo leans in to observe the result of Izuku's attempt, frowning thoughtfully. It's not exactly the same as her Creation, but she's able to apply some of the same principles. ]

The copper is undergoing a chemical transformation when you transmute it. The atoms get excited, and release energy, causing the copper to heat up. If you try to shape it more slowly, you might be able to prevent it from overheating.