How do I find the slope of this graph?​

Not exactly But you can take the slope of the curved portion and the slope of the flatline.

It wont do you much good since your working for absorbance but if you ever see something like a temperature change you can use the slope(s) to find freezing points/melting

Explanation:

If you need to submit a slope you could use a best fit which is just point to point or you could break it up like i mentioned

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.