Calcium cycle in chemistry teaching at the lower secondary school

The research is focused on the use of experimental calcium cycle in chemistry teaching at the lower secondary school. The cycle is based on four reactions: 1. thermal decomposition of calcium carbonate, 2. reaction of calcium oxide with water, 3. calcium hydroxide with hydrochloric acid, 4. reaction of calcium chloride with sodium carbonate. The calcium cycle was tested at lower secondary schools (and equal classes from comprehensive schools). Despite the difficulty of taking some steps, the cycle was accepted by both teachers and learners.