Lee conducts an experiment to see if mass is conserved when a piece of charcoal is burned for 5.0 minutes. He measures the mass of the charcoal before lighting it with a match. At the end of 5.0 minutes, Lee puts out the fire by suffocating it. After the charcoal has cooled, he measures its mass again. His data are below.
Initial Mass | Final Mass
.415 | .289

Charlene tries to repeat Lee's experiment by using a different piece of charcoal. But she burns the charcoal for just 3.0 minutes and collects all of the gas and dust released by the burning charcoal. She then weighs the total mass of these objects. Her results are below.
Initial Mass | Final Mass
.498 | .498
Charlene's experimental results indicate that mass was conserved. Why do Lee's results indicate that mass was not conserved?

He burned the charcoal for a longer period of time than Charlene did.

He did not collect the gas and dust released by the burning charcoal.

He forgot to measure the mass of the charcoal while it was still burning.

Mass is not conserved when an object undergoes a chemical change.