Which of the following is an examples of chemical change?

Burning of paper

Rusting of iron

Explanation:

Rusting of iron is a chemical change because a new substance iron oxide is formed. The presence of oxygen and water or water vapour is essential for rusting. Rusting of iron is a continuous process which slowly eats up the iron objects and makes them useless.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.