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. Which of these provides evidence that a chemical reaction occurs?
(1 point)
Responses
A gas is present
A gas is present
The total number of atoms remains unchanged.
The total number of atoms remains unchanged.
The state of matter remains the same.
The state of matter remains the same.
A brown gas is produced.
A brown gas is produced.
Students mixed two liquids in a beaker and listed their observations.
Based on these observations, which statement contains the best evidence that a chemical reaction occurred?
(1 point)
Responses
There is a change in shape.
There is a change in shape.
There is a change in volume.
There is a change in volume.
The two liquids mix into a solution.
The two liquids mix into a solution.
The two liquids form a new substance.