I think second grade is the most important in elementary or perhaps any level of education. In literacy, it is when kids are starting to read little chapter books, It is when the should have mastered the basic phonics rules and can handle lots of basics. Here's a good set of info for 2nd grade spelling lists and I quote
Second grade spelling word lists include Dolch and Fry sight word lists and word structure lists (compound words). Second grade students can build sight word fluency and phonics mastery through the use of VocabularySpellingCity’s interactive online games. Second grade games feature both audio and visual elements, an effective learning tool for all maturing readers and writers, specifically English Language Learners (ELLs).
Looking at science, here's a great second grade science program and some support for second grade science vocabulary words.
And I quote some science curriculum educational materials from Science4Us which is based on the 5E Instructional Model as developed by Roger Busby at BSCS in Colorado Springs in Colorado, currently run by DCE as Executive Director. This info on 2nd grade science is from the Science4Us website, and I quote:
In our second grade curriculum, students will demonstrate an understanding of scientific inquiry, including the skills, processes, and tools necessary to conduct a simple scientific investigation. In Life Science, students will show knowledge of the needs and characteristics of animals and the way they interact with their own distinct environments. In the Weather unit, students will understand different weather elements and how weather can be observed and measured using tools. From the Magnets unit, students will learn about the force and motion through the properties of magnetism