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Theraml Decomposition year 8 chemistry Questions
🔥 Thermal Decomposition – 20 Practice Questions
1. Define thermal decomposition.
A reaction in which a compound breaks down into simpler substances using heat.
2. What does thermal mean?
Heat.
3. Is thermal decomposition endothermic or exothermic?
Endothermic.
4. Complete: CaCO₃ → (heat) → ______ + ______
CaO + CO₂
5. Which gas turns limewater milky?
Carbon dioxide (CO₂).
6. True or False: Thermal decomposition is a physical change.
False. It is a chemical change.
7. What colour change occurs when copper carbonate is heated?
Green to black.
8. Write the word equation for calcium carbonate decomposition.
Calcium carbonate → Calcium oxide + Carbon dioxide
9. Which type of substance decomposes – element or compound?
Compound.
10. Multiple Choice: Which is thermal decomposition?
A) H + O → Water
B) CaCO₃ → CaO + CO₂
C) Fe + O → Rust
B
11. Why is heat required in thermal decomposition?
To break chemical bonds.
12. What solid is formed when CuCO₃ is heated?
Copper oxide (CuO).
13. Complete: MgCO₃ → (heat) → ______ + CO₂
MgO
14. True or False: Energy is released in thermal decomposition.
False. Energy is absorbed.
15. What test confirms the presence of CO₂ gas?
Limewater turns milky.
16. What happens to bonds during decomposition?
Bonds are broken.
17. Give one industrial use of thermal decomposition.
Producing calcium oxide for cement manufacture.
18. Is a new substance formed in thermal decomposition?
Yes.
19. What type of reaction is the opposite of decomposition?
Combination reaction.
20. What are the two products when CaCO₃ is heated?
Calcium oxide and carbon dioxide.