Explain why thermal decomposition of a metal carbonate may appear to lose mass when carbon dioxide escapes.

In the subtopic Mass changes when a reactant or product is a gas, this learning objective focuses on explain why thermal decomposition of a metal carbonate may appear to lose mass when carbon dioxide escapes. It sits within Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations for AQA GCSE Chemistry 8462 Unit 4.3, so the explanation must stay anchored to quantitative chemistry rather than drifting into a general chemistry idea. Approved keywords to use include thermal decomposition, carbon dioxide. Carbon dioxide. means a colorless, odorless gas produced during the thermal decomposition of metal carbonates Avoid the mistake of students often think that the mass of a metal carbonate decreases because the metal itself is lost during thermal decomposition; instead, explain that the mass loss is due to the escape of carbon dioxide gas, not the loss of the metal. Emphasize that the remaining solid product still contains the metal For exam answers, when studying thermal decomposition, remember that the escape of carbon dioxide gas can lead to an apparent loss of mass. Always relate this to the conservation of mass principle