define a chemical reaction .state four observations which help us to determine that a chemical reaction has taken place. write one example of each observation with a balanced chemical equation.
Answers
Chemical reaction is a process in which one or more reactants are converted into products. The product may be one or more. The chemical reaction can involve an element or a compound which leads to the formation of product or products.
The observation which may be used to show that a chemical reaction has taken place may include;
1. Change in colour- Reaction of Bromine and ethene
( Br2(l) + C2H4⇒ CHBrCHBr)
2. formation of a precipitate- silver nitrate and NaCl
(AgNO3 (aq) + NaCl= AgCl(s) + NaNO3)
3. Temperature change
4. Change of smell
a process in which two or more substances reacts to form some other new substances with new set of properties is called Chemical reaction.
1)change in colour
Zn+CuSO4------ZnSo4+Cu
the colour of cuso4 changes from blue to pale green
2)change in temperature
Zn + H2SO4------ZnSO4 +H2
heat is evolved