>>12523569many "hot" compounds, like acid chlorides and organoboranes will fume slightly when you expose them to air
Bubbling is bad when you're boiling things, because the bubbles splash shit everywhere, contaminating both your compound and your apparatus. But when a reagent liberates CO2 or N2, that can be a good trick to drive a difficult reaction forwards (le chatlier's principle)
Yellow is the most common color. Transition metals tend to produce blues/greens/oranges, etc. Tar tends to be reddish orange. Slightly oxidized amines turn yellow then brown.
>Where did this stereotype come from?chemistry is mostly invisible - there's often no way to tell if what you're doing is really working. Before spectroscopy became common place, an array of color-changing tests and indicators would be needed to figure out even the most simple reaction. Even today, most hobby chemists are stuck with this shit.
Picrel gives an idea of what these tests are like - three rows of test tubes, muddy colors, trying best to figure out if it's "deep orange" or "very orange"
