9. Which of the following statement is incorrect? (A) Across a period from Sc to Cu, the densities increase with
increasing atomic number
(B) The noble character of transitions metals is due to high
ionization energies, high enthalpies of solvation and higher
thalpies of sublimation
(C) on going down a group from 3d to 6d series, the stability
of higher oxidation state increases with stability of high
oxidation state increases with increasing atomic numbers
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here's the link to your question!

explanation:

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

one negative thing it that it can kill water animals. another negative thing is it can cause the destruction of ecosystem. one way water pollution can be reduced is to conserve energy.