Those would be called indicators , simply google them and you should find many. I'll leave some examples "bromophenol blue" "Methyl red" and "phenol red".
A covalent bond? Not sure how much detail you want, sorry
Answer:
The Glossopteris fossil is found in Australia, Antarctica, India, South Africa, and South America—all the southern continents. Now, the Glossopteris seed is known to be large and bulky and therefore could not have drifted or flown across the oceans to a separate continent
Explanation:
Your welcome
In a balloon there is a low pressure within the balloon. This means that the particles are more spaced out. Wheras in the cylinder they are under high pressure, meaning that the particles are much closer together!