Burning a substance inside a sealed glass vessel does not change the total weight.

Judge as of 2025-09, as a physical/historical claim (Lavoisier/Boyle-type experiments). True: chemistry references confirm that combustion in a sealed vessel leaves the total mass unchanged within measurable precision (conservation of mass), as shown historically. Mostly true: this holds, with only the negligible relativistic mass change from energy released, or minor experimental caveats. Mixed: not applicable unless sources disagree substantially. Mostly false: measurable weight changes typically occur in a properly sealed vessel. False: the weight demonstrably changes in a sealed vessel.

Set before the research began.

1. E1 The Aristocrat who revolutionised chemistry: Before Madame Guillotine claimed him, Antoine Lavoisier transformed chemistry into a modern science with his revolutionary set of terms and symbols | New Scientist New Scientist · 17 April 2024

   “Lavoisier, however, weighed the vessels – still sealed – with tin and lead inside them. He found that they weighed the same before and after burning.”

2. E2 The Dawn Science and Technology Kanazawa Institute of Technology

   “In one of these experiments Lavoisier burnt tin and plumbum in a closed vessel and confirmed that the weight of metal-ash increased when the weight of air decreased, although the weight of the whole vessel remained unchanged.”

3. E3 Lavoisier and the Law of Conservation of Mass ChemTeam (chemteam.info) · 25 November 2025

   “Lavoisier was able to assemble a number of experiments, all done in closed vessels, in which the weight remained constant, within experimental error.”

4. E4 The Aristocrat who revolutionised chemistry: Before Madame Guillotine claimed him, Antoine Lavoisier transformed chemistry into a modern science with his revolutionary set of terms and symbols | New Scientist New Scientist · 17 April 2024

   “He attributed the gain in weight that he observed to material particles of fire passing through the pores of the glass and combining with the metals.”

Independent sources report that Lavoisier weighed sealed vessels containing tin and lead before and after burning and found the same weight (E1, E2). E3 says his closed-vessel experiments kept weight constant within experimental error. E4 reports an earlier observed weight gain attributed to particles of fire passing through the glass, but E1 reports that Lavoisier's sealed-vessel weighing found no change. The evidence therefore supports conservation of mass in a sealed vessel, within measurable precision.