NSES Content Standard A
Science as Inquiry: Understanding about scientific inquiry 
Grades K-4, page 123 

Scientists use different kinds of investigations depending on the questions they are trying to answer. Types of investigations include describing objects, events, and organisms, classifying them and doing a fair test (experimenting). 

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.