9. Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural sources, such as forest fires, lightning,
and microbial activity in soil. The equation for producing nitrogen dioxide is shown
below.
2NO
Colorless
gas
+ 02-2NOZ
Colorless
Brown
gas gas
Which of these provides evidence that a chemical reaction occurs?

answer

fusion: the energy source of stars. the energy released from the collapse of the gas into a protostar causes the center of the protostar to become extremely hot. when the core is hot enough, nuclear fusion commences. fusion is the process where two hydrogen atoms combine to form a helium atom, releasing energy.

hope it

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

b.

the accuracy of the data.