Asubstance undergoes a change. which of the following indicates that the change was a chemical change?
a. the substance changed shape.
b. new molecules formed.
c. the substance froze.
d. the substance changed size.

How have the greenhouse gasses increased from the year 2000 to 2018

Draw the structure for 5-isopropyl-2-methyl-3-nonene

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!