Update: Based on the lively discussion here, there is now a featured meta post where you can propose specific changes.
When users ask their first question, they now are shown the following information (to see this, log out or open a private browser window and go to https://chemistry.stackexchange.com/questions/ask):
To give an example of what another site did, below is the modified information from Code Golf, which they requested after discussing it on their meta.
Physics mentions homework-like questions not on the "first-question" prompt but always as step 1 of asking a question:
In contrast, our step 1 directions are much shorter and without links (maybe some of the physics language could go into the "first-question" box, or into the step 1 side-bar):