LEARNING SCIENCE THROUGH ACTIVE LEARNING.

LABORATORY EXPERIMENT AN ACTIVE METHOD

Chemistry is an experimental science, which has the laboratory experiment as a method of scientific investigation and as a learning method.

Laboratory experiment is a method of acquiring knowledge, training skills, intellectual and practical working skills. It is an active learning method for deducting theoretical information, evaluating, thoroughgoing study and strengthening knowledge.

Laboratory experiment follows hierarchical steps of teaching, leading the student from observing chemical phenomena, deduced on the basis of demonstration, to the observation of the phenomen through his own activity (the phase of concrete operation forming). Then they check and put them in practice (formal operations phase), when the formal structure of the intellect crystallizes and they are led further to the interpretation of the observed phenomen which correspond to the highest stage of the development hierarchy ( the phase of synthetic operations).

The functions of the laboratory experiment - The reproductive function – corresponds to the first step in which the practical skills are formed in the laboratory - The creative– productive function - corresponds to the interpretation and analysis of experimental results developed in scientific investigation and materialized in the interest of the student in the teaching strategy used.

Organizing a laboratory experiment Laboratory experiments can be organized differently ; formulating the specific tasks to perform an experiment involves issues such as: learning purposes, a higher accessibility to learn, the content of learning, the place of the process of learning, linking with other teaching strategies.

IRON CORROSION The corrosion is a process in which metals are converted into oxides or other compounds. This process causes a gradual damage of the metals. In this experiment they investigate some of the factors involved in the corrosion process.

Necessary substances and tools  4 new nails  copper wire  a Zn band  agar ( gelatin)  water  K 3 [Fe(CN) 6 ] 0,1M  phenolphthalein 0,1%  2 Petri boxes

How to work  Prepare about 100 ml agar solution as it follows:  Heat about 100 ml distilled water to a gentle boil. Add 1 g of agar powder. Continue heating and stir until agar is dispersed. In the agar solution about 5 drops of 0,1 M potasium ferricyanide and 3 drops of 0,1% phenolphthalein solution are added. Shake it.

The four new nails are prepared as it follows:  One right – angled bend  One surrounded with a copper wire  Another will be surrounded by a zinc band  The fourth remains unchanged

 In a Petri box put a normal nail and the right-angled bent one and in another Petri box put two nails surrounded by copper wire and zinc band, without touching each other.  Add carefully the warm and still fluid solution in Petri boxes until the nails and the pieces attached are covered with about 0,5 cm of liquid.  Students notice what happens to the boxes. The boxes are kept till the next day when new observations are made.

CONCLUSIONS Corrosion occurs rapidly when the subject suffers mechanical stress. Some metals such as magnesium and zinc delay rusting and metals less active than iron accelerates corrosion. Magnesium and zinc in contact with iron anode and force iron to act as a cathode and it doesn’t corrode.

The reactions of Al (Aluminium) with NaOH (Sodium hydroxide) Reagents and tools: -an Al sheet -solid NaOH -water -a watch glass

Working mode/ Procedures: We put some caustic soda crystals over a piece from the Al sheet, then we add the water, step by step, in small portions.

The equation of the reaction: Conclusion: The Al reacts with NaOH, forming a complex combination:

This project has been funded with support from the European Commission. This publication reflects the views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.