Demonstrations are such great tools in the classroom. A huge commitment for the teacher in time and resources but the resulting engagement of students can make up for that effort.
The link above is to a lesson plan on how to mix different syrups to mimic the different types of lava flow. Unfortunately after opening the link once I have not been able to do so again. I have sent an email to the teacher who created the lesson in hopes she can send a better link.
I also found the following activity written for middle school students. Great name and fun for students.
This plan includes great links and materials to complete the lesson.