Question

hoe do we know a chemical reaction has taken place

Answer 1

We can tell if a chemical reaction has taken place when one or more of the following things happen: There has been a colourchange inside the reaction flask. A gas has formed. Usually weknow a gas has formed when we can see bubbles.



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Answer 2

1. chamgement in temperature
2. change in state .
3. produce heat.
4. evolution of gas