Your question is a great one! Mechanical and Civil Engineering are two branches of engineering that share many similarities. Both of them will require you to take a chemistry course (or two). In order to be an effective mechanical/civil engineer, you need to understand how different kinds of materials behave. Different materials have different properties (flexibility, strength, electrical and thermal conductivity, etc.) that make them useful for different applications. For example, you wouldn't want to build a bridge out of rubber, because it would bend when weight was put on it! Before you can understand the more complex properties of materials, you need some basic understanding of chemistry. When I was studying to be a mechanical engineer, I had to take one chemistry course, then a couple of materials courses that extended what I learned in chemistry class.
I hope this answered your question. I wish you luck on your chemistry project and as you study to be an engineer!