290 List of Experiments

Transcription

1 List of Experiments 3.7 Experiments on Substances and Their Properties E3.1 Heating a Copper Envelope...52 E3.2 Heating of Copper in Vacuum and in Air...53 E3.3 Decomposition of Silver Sulfide or Silver Oxide...53 E3.4 Reaction of Copper Oxide with Hydrogen...53 E3.5 Evaporation of Acetone...54 E3.6 Condensation of Butane Gas Under Pressure...54 E3.7 Dissolution of Metals...55 E3.8 Dissolution of Grease...56 E3.9 Burning Metals on a Balance...57 E3.10 Conservation of Mass by Burning Charcoal...58 E3.11 Burning Candles on a Balance...58 E3.12 Reaction of Carbon Dioxide with Magnesium...60 E3.13 Density of Air and Carbon Dioxide...61 E3.14 Properties of Hydrogen and Other Colorless Gases...61 E3.15 Composition of Air Experiments on Particle Model of Matter E4.1 Growing of Alum Crystals...93 E4.2 Close-Packing Model for the Alum Crystal...94 E4.3 Electrostatic Forces for a Bonding Model...94 E4.4 Silver Crystals from a Silver Salt Solution...94 E4.5 Cubic Close Sphere Packings as Models for a Silver Crystal.. 95 E4.6 Solution of Iodine in Ethanol...96 E4.7 Sphere-Model for the Solution of Iodine in Ethanol...96 E4.8 Reaction of White and Red Phosphorus with Oxygen E4.9 Volumes of Liquid and Gaseous Ethanol...97 E4.10 Model Experiments for the Three States of Matter...98 E4.11 An Empty Flask is Full of Air...98 E4.12 A Flask Contains Nothing

2 290 List of Experiments 5.5 Experiments on Structure Property Relationships E5.1 Silver Crystals Through Electrolysis E5.2 Closest Sphere Packings as Models for Metal Crystals E5.3 Cubic Closest Packing as a Model for Silver Crystals E5.4 Ductility of Different Metals E5.5 Formation and Decomposition of Sodium Amalgam E5.6 Nitinol A Memory Metal E5.7 Freezing Point Temperatures of Solutions E5.8 Structural Models for the Sodium Chloride Structure E5.9 Destruction of Salt Crystals E5.10 Electric Conductivity of Salt Crystals, Melts and Solutions. 137 E5.11 Heat of Crystallization from Molten Salt E5.12 Precipitation of Salt Crystals from Solutions E5.13 Electric Attraction and Repulsion Forces E5.14 Ionic Bonding and Magnetic Model E5.15 Magnetic Force Fields Experiments on Chemical Equilibrium E6.1 Melting Equilibrium E6.2 Solubility Equilibrium of Salt E6.3 Model Experiment on Dynamic Equilibrium E6.4 Solubility Equilibrium of Sodium Chloride E6.5 Solubility Equilibrium of Calcium Sulfate E6.6 Boudouard Equilibrium E6.7 Quantitative Decomposition of Ammonia Experiments on Acids and Bases E7.1 Decomposition of Sugar Using Sulfuric Acid E7.2 Reaction of Metals with Sulfuric Acid E7.3 Limestone Deposit Removers Acidic Household Cleaners E7.4 Drain Cleaner an Alkaline Household Chemical E7.5 Reaction of Several Acid Base Indicators E7.6 ph Values of Several Bathroom and Kitchen Chemicals E7.7 Electrical Conductivity of Solutions of Acids, Bases and Salts E7.8 Hydrochloric Acid from Solid Sodium Chloride E7.9 Hydrochloric Acid from Gaseous Hydrogen Chloride E7.10 Sulfuric Acid and Water a Strong Exothermic Reaction E7.11 Reaction of Calcium Oxide and Water E7.12 ph Values by Dilution of Hydrochloric Acid E7.13 Reaction of Calcium Hydroxide Solution with Carbon Dioxide E7.14 Neutralization Reactions E7.15 Conductivity Titration of Baryta Water with Sulfuric Acid Solution E7.16 Heat of Neutralization

3 List of Experiments 291 E7.17 ph Values of Strong and Weak Acids E7.18 ph Values of HCl and H 2 S Solutions Experiments on Redox Reactions E8.1 Precipitation of Copper from Copper Sulfate Solution E8.2 Exothermic Precipitation Reactions E8.3 Precipitation of Silver from Silver Nitrate Solution E8.4 Precipitations with Other Metals E8.5 Metals in Acidic Solutions E8.6 Metals in Salt Solutions E8.7 Galvanic Cells E8.8 Iron Corrosion E8.9 Leclanche Battery E8.10 Lead Accumulator Experiments on Complex Reactions E9.1 Existence of Complex Ions E9.2 Blue and White Copper Sulfate# E9.3 Octahedral Models of Complex Particles E9.4 Properties of the Ammine Copper Complexes E9.5 Determination of the Coordination Number E9.6 Copper Complexes and Stability E9.7 Nickel Complexes and the Octahedral Structure E9.8 Synthesis of Hexa Ammine Cobalt Chloride Crystals E9.9 Copper Complexes and Equilibrium E9.10 Cobalt Complexes and Equilibrium E9.11 Dissolving Aluminum Hydroxide by Complex Reactions E9.12 Dissolving Silver Halogenides by Complex Reactions Experiments on Energy E10.1 Masses and Exothermic Reactions E10.2 Energy Transfer During Exothermic Reaction E10.3 Energy Transfer During Endothermic Reaction E10.4 Temperatures of Ice Water Mixtures E10.5 Specific Heats of Water and Glycol E10.6 Efficiency Level E10.7 Quantitative Combustion of Pure Carbon E10.8 Quantitative Oxidation of Butane E10.9 Explosion of Gasoline Oxygen Mixtures E10.10 Molecular Models for Hydrocarbon Oxygen Reactions

4 Epilogue Misconceptions: They are hard; they have no rules; they are unstructured! The caption in one of Gary Larson s comics seems to best summarize this: Shhhh, Zog!...Here comes one now! The work in this book represents a thorough and significant advance in the study of student misconceptions in chemistry. The research reported here, conducted in Germany, the United States, and Ethiopia, explored several common misconceptions about chemistry, and examined diverse ideas of conceptual change that describe how to correct or prevent such misconceptions. This research adds to existing studies in two major ways: (1) it extends the diagnostic study of students misconceptions, and (2) it uses a research methodology that allows for the testing of new approaches and strategies to avoid and cure this problem. In this direction one has to differentiate preconcepts and school-made misconceptions: the first ones are brought by young students from observing every-day life, the second ones are developed by inappropriate teaching or by difficult chemistry contents. Empirical studies of the last decades show that in many countries the same misconceptions are found year after year and nothing changes to improve the situation. So the authors suggest several meaningful ways to prevent and deal with students chemistry misconceptions. The first reported way is about students initially performing key experiments, followed by discussion of their ideas and understanding, and finally teaching the chemistry concept. The second approach starts by teaching the scientific concept, recounting students individual misconceptions, finally comparing and defending the new attained chemistry concept by constructively criticizing their prior knowledge. Both ways involve the use of structural models and model drawings which help in the development of students mental models to facilitate their understanding of the 3-D arrangement of atoms and ions the base of understanding chemistry. In addition, students will improve their spatial ability with the use of structural models. We urge everyone to apply the ideas in this book in his or her classroom presentations. Even with limited time and materials, some of the smaller, more simple changes can be accomplished. The authors hope that this book will stimulate serious discussions at all educational institutions to cure preconcepts and successfully to prevent school-made misconceptions. We expect that these 293

5 294 Epilogue fruitful debates and studies will also take into account the need for new or reallocated methods to implement and support improved presentations of chemical material. We welcome comments about this work from students, teachers, and college-level faculty members. In conclusion, we believe that the research and practical contributions of our studies will inspire future research in this area. Indeed, the design and the results of these studies will provide useful background for replication and expansion to other areas and topics in school and college STEM (Science, Technology, Engineering and Mathematics) courses. College STEM departments could also invite colleagues from schools or colleges of education to focus on issues of teacher preparation and professional development. This will also help improve the scientific literacy of all. A final thought: We would like to quote Albert Einstein, You do not really understand something unless you can explain it to your grandmother. This is not just a cute and interesting statement, but it is also true. We hope that, with the help of to the material presented in this book, more grandmothers will receive clear and truthful explanations and fewer chemistry misconceptions.