Conve fo
a Calculate the percentage oxygen in the air using this data.
b Explain why the answer is not the same as you had expected and how
the experiment could be improved.

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

it means there are 3 atoms of oxygen

a electronegativity decreases beacuse the size of nucleus is bigger.