What are the factors that determine the level of harm an introduced chemical has on the environment?

they can damage the atmosphere

Explanation:

if you release bad chemicals into the atmosphere it affects the air

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )

0.11 m/s and 0.28 m/s should be correct