During an experiment, a student observes the formation of a precipitate. why does this indicate that a chemical reaction is likely occurring?

1)a solid forms, and there is a change of color.
2)a gas forms, and there is a change of color.
3)a solid forms, and light is emitted.
4)a gas forms, and light is emitted.

Which statement about the stamps is correct?

What are the primary responsibilities of a chemical engineer involved in "r& d"? develop large scale manufacturing operations discover new products and processes training of new chemists determine products needed by consumers

Essay-alternative energy sources research sources of energy that are being developed. write a report of 350-400 words discussing the information you learned concerning the development of various energy sources and the impact that you think they will have on your life. include sources cited at the end of your report using the mla format. follow the rubric guidelines. note that wikipedia is not an appropriate resource for a research paper. worth 99