We observe and study substances


Vaporization is a process when liquid state changes into gaseous. It is causedby escape of a molecule of a substance from liquid phase to gaseous phase. Molecules in a liquid move freely and in a disorganized way. When they reach a certain speed they are able to „escape“, they leave the surface of the liquid as gas molecules.This process is called vaporization. Various liquids, despite the same conditions, evaporate at different speeds. Acetone evaporates very quickly; alcohol evaporates a little slower and water the slowest. Liquids which evaporate quickly are called volatile. The speed of evaporation depends on the boiling point of a liquid. A tabulated value of acetone boiling point is 56 °C, ethanol 78 °C and water 100 °C.Liquid which is evaporating, takes in the warmth from its surroundings and due to this it cools down its surroundings. Therefore a thermometer which is wrapped in a piece of cotton wool and soaked in the most volatile liquid, will measure the lowest value.

Pupils will be gradually introduced to each task assignment. First, they formulate their estimate of the process and outcomes of the experiment and write it into the prepared table in their worksheet. Then they verify their hypothesis while doing the experiments according to the teacher´s instructions.The teacher asks pupils to divide themselves into working groups. Groups of between 2-4 pupils are ideal.