Q1
What is a combination reaction?
AForming one product from reactants
BBreaking one substance apart
CAn element replacing another
DNo reaction occurring
ICSEClass 9 (ICSE)ChemistryCh 2 · Topic 1
Chemical Changes and Reactions
Chemical reactions transform reactants into products through processes like combination, decomposition, displacement, and double displacemen
Core concept
A combination reaction forms one product from two or more reactants, like hydrogen and oxygen combining to form water.
How it works
A decomposition reaction breaks down one compound into simpler substances, often needing heat, light, or electricity as energy input.
Why it matters
A displacement reaction occurs when a more reactive element replaces a less reactive one in a compound, like zinc displacing copper from copper sulfate.
Key detail
A double displacement reaction involves an exchange of ions between two compounds, often producing a precipitate (insoluble solid).
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• Combination reaction: forms one product from reactants.
• Example: hydrogen + oxygen forms water.
• Decomposition breaks compounds into simpler substances.
• It often needs heat, light or electricity.
• Displacement: reactive element replaces less reactive one.
• Example: zinc displacing copper from copper sulfate.
• Double displacement exchanges ions between compounds.
• This often produces a precipitate.