Cement and concrete
Secure a small bag of Portland cement. Have the pupils mix it with water and put it in tin can covers, paper cups, or small pasteboard boxes unless it hardens. Study its appearance and its properties. Break a piece of cement and study it. Mix the dry cement with about twice as much sand or gravel. This will form concrete. After adding water and mixing thoroughly place it in moulds. Permit these to arden various days. Again study the appearance and the characteristics of these samples.