Materials
1: Easy to get from supermarket or hardware store
2: Available in most school laboratories or specialist stores
3: Requires materials not commonly found in school laboratories
Difficulty
1: Can be easily done by teenagers
2: Can be done by science teachers
3: May require a more experienced teacher
Safety
1: Minimal safety procedures required
2: Some safety procedures required to perform safely
3: Only to be attempted with adequate safety procedures and trained staff