NSES Content Standard A 
Science as Inquiry: Understanding about scientific inquiry
Grades 5-8, page 148

Different kinds of questions suggest different kinds of scientific investigations. Some investigations involve observing and describing objects, organisms, or events; some involve collecting specimens; some involve experiments; some involve seeking more information, some involve discovery of new objects and phenomena; and some involve making models.
 
 
Benchmark 1B The Nature of Science: Scientific Inquiry
Grades 3-5, page 11
Scientific investigations may take many different forms, including observing what things are like or what is happening somewhere, collecting specimens for analysis, and doing experiments. Investigations can focus on physical, biological, and social questions.

Benchmark 1B The Nature of Science: Scientific Inquiry
Grades 9-12, page 13
Sometimes, scientists can control conditions in order to obtain evidence. When that is not possible for practical or ethical reasons, they try to observe as wide a range of natural occurrences as possible to be able to discern patterns.