ComLab Conference 2007 November 30 - December 1, 2007 Radovljica, SLOVENIA 1 Computerised experiments on chemical processing – drying and evaporation Erika Mechlova, Libor Konicek and Boleslav Taraba University of Ostrava 30. dubna 22, Ostrava, the Czech Republic, E-mail: [email protected] , [email protected], [email protected] Abstract – Drying and evaporation are chemical processes which depend on materials. Some experiments are described with computer support of measurement and results of there with using different materials. The measurements were carried out by different computer aided systems and different force sensors for measurement of weight-shortage of water. Keywords – Science school Laboratory, e-ProLab CMC-S3, chemical processes 1. INTRODUCTION Submitting experiment is modelling experiment for school lessons in simplified approach. The main aim of experiment is drying four different materials and comparison evaporation water from different porous materials with different size of por ous. 2. CHEMICAL PROCESSES – EVAPORATION AND DRYING Evaporation is extraction of liquids from the surface of liquids or solid state bodies. Drying is extractions some water that are in wet solid state materials or solutions. The water must be removed from wet solid state material or aqueous solution before the required compounds can be properly characterized. There are many ways to do this extraction. For example in the organic chemistry are commonly used two methods of drying solutions: saturated aqueous sodium chlorate and solid drying agents. In technical practice the drying is carried out in dryer by the direct contact of wet material with drying gases that are air and burnt gas in special chamber. Technical drying demands expensive equipment. Suggested experiment of evaporation and drying is modelling experiment for school lessons in simplified approach. 3. DESCRIPTION OF SAMPLES AND SET UP OF EXPERIMENT 3.1 Description of samples Four different samples of materials will be warming up in the same way. Samples have different capillary. Samples are in Petri dish diameter 9 cm, see Fig. 1. All samples have the same size. The first sample serves as comparative sample with free distilled water surface. The second one is filtering paper with small capillaries. The third one consists of glass pellets diameters of 6 mm with big capillaries. The fourth sample is pellets of silica gel with microcapillaries; silica gel is hygroscopic material that you can receive from sachets that are around electric appliances to absorb humidity during transport of these things. Fig. 1. Samples of material in Pertri dishes. All samples are dampened by pouring distilled water to the same heights of Petri dishes. Amount of distilled water is 25 ml. Petri dishes are placed on aluminium plate the same size as Petri dishes. 3.2 Set up of experiment Drying air is warming by heater that is about 30 cm below the samples and warm air flows up to the samples, see Fig. 2. Heater is regulated to 40 W. Every Petri dish is lying in horizontal aluminium plate of ISES force sensor with horizontal aluminium plate. Force sensors demand symmetrical voltage ±12 V. T his voltage is received by reduction of connector Canon 15 pin to the CMC-S3. Signals are connected to analogue inputs. Range of the ISES force sensor is from –2,5 N to +2,5 N. All four ISES force sensors are connected to CMC-S3.