Question

Define a chemical reaction. state four observtaionswhich help us to determine that a chemical reaction has taken place

Answer 1

It is a chemical change which involves the formation of new substances.

Answer 2

$\huge\bf {\underline {\underline \pink{ƛƝƧƜЄƦ}}}$

(i) Evolution of gas: The chemical reaction between zinc and dilute H 2SO 4. (ii) Change in colour: The chemical reaction between potassium iodide solution and lead nitrate solution. (iii) Formation of piecipitate : The chemical reaction between sulphuric acid barium chloride solution.