Question

what is the evidence that the gas made in the mentos + soda demo was carbon dioxide?
your answer
which of these is the most reliable way to see if a new gas has formed?
fill up a balloon
flame test
measure temperature
look at it
how does hydrogen react in a flame test?

Explanation:

• For the first question, in the Mentos + soda demo, carbon dioxide is the gas produced. Soda (carbonated drinks) contains dissolved carbon dioxide. When Mentos are added, the rough surface of Mentos provides nucleation sites for the dissolved carbon dioxide to come out of solution rapidly, creating the "fizzing" effect.
• For the second question, a flame test is a reliable way to test for some gases (e.g., hydrogen gives a 'pop' sound, carbon dioxide extinguishes the flame). Filling a balloon can show gas presence but not identify it uniquely. Measuring temperature and looking at it are not reliable for gas identification.

Answer:

• First question: The soda already contains dissolved carbon dioxide, and Mentos provide sites for it to escape rapidly (fizzing is evidence of gas release, and since it's from soda which has \(CO_2\) as the dissolved gas for carbonation, it's \(CO_2\)).
• Second question: Flame test.