I'm intrigued by the phrase that they have "no idea what science is about..." Look at the science and engineering principles; I am sure your will find that those children's actions are well represented. Beyond that, so much depends on the grade and interests of your students.
Once you have an idea of your student interests, look at the Early Years column, or keyword that interest in the learning center. That will give you lots of ideas.
To put those ideas into action, you need to think backwards. What experiences do they need to have so that they can do X. You may have to directly teach some skills, such as how to use a magnifying glass. If so, I'd do that before you teach the content