The present study contributes to the discussion that goes on during recent years about  children’s intuitive knowledge about the natural world and its consequences on the teaching of science. Our aim has been to study the knowledge about the changes that occur at the macro and submicro levels during the dissolution of salt in water, and how this knowledge develops with time.  Pupils 8-18 years old were interviewed individually, answering six questions while observing an experiment of dissolving salt in water. It was found that the pupils found it difficult to understand what happens, while they have difficulty to abandon their initial intuitive conceptions, despite the teaching of chemistry at school. They used a small re-occurring number of answer types, with a constant distribution over the various age groups, while only one among the elder pupils provided scientifically acceptable answers.