# Copper carbonate decomposes when heated. The equation for this reaction is: CuCO₃ → CuO + CO₂. Explain why the total mass of the products formed in this reaction equals the mass of the copper carbonate that was heated.

> Eduqas A-Level Chemistry — 3.6 Amines and polymers (A-Level only) · Explain · 5 marks

## Mark scheme (5 marks)

1. No atoms are lost or made during a chemical reaction (law of conservation of mass)
2. The mass of the products equals the mass of the reactants
3. The same atoms that were in the copper carbonate are present in the products (copper oxide and carbon dioxide)
4. The equation is balanced, meaning the number of each type of atom is the same on both sides
5. Even though CO₂ is a gas that is released, its mass must still be included / accounted for in the total mass of products

## Key terms

- [products](https://www.gradenine.co.uk/glossary/products)

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