Teaching Chemical Tests

Please note that all record sheets and blackline masters may be copied and used in conjunction with the teaching of this unit. 

Student Activity Book The Chemical Tests Student Activity Book accompanies the Teacher s Guide. Written specifically for students, this activity book contains simple instructions and illustrations to help students understand how to conduct the activities in this unit. The Student Activity Book also will help students follow along with you as you guide each lesson, and it will provide guidance for students who may miss a lesson (or who do not immediately grasp certain 

The lessons in the Student Activity Book are divided into the following sections, paralleling the Teacher s Guide  

Classroom Discussion Class discussions, effectively led by the teacher, are important vehicles for science learning. Research shows that the way questions are asked, as well as the time allowed for responses, can contribute to the quality of the discussion. 

Brainstorming Brainstorming is a whole-class exercise in which students contribute their thoughts about a particular idea or problem. When used to Introduce a new science topic, it can be a stimulating and productive exercise. It also is a useful and efficient way for the teacher to find out what students know and think about a topic. As students learn the rules for brainstorming, they will become more and more adept in their participation. 

---

In the section Teaching Chemical Tests, on pgs. 9 to 14, you will find a detailed discussion about the assessment of students learning. The specific goals and related assessments for this unit are summarized in Figure T-l on pg. 10. Please keep in mind that some third-graders may not completely understand every concept listed or master every skill. As you observe your class, look for the development of these ideas and skills in your students rather than their mastery. 

Note Your students will be working in teams of two from now through Lesson 10. (See Teaching Chemical Tests on pg. 7 for information on effective team building.)... 

On the Safety Rules poster, write Wear goggles when working in science class and Follow directions carefully. Tell students they will help you add to this list as they progress through the unit. (The Teaching Chemical Tests section on pg. 7 suggests additional safety rules.)... 

A chemistry scheme of work based on the syllabus requirements was developed for the year in collaboration with all teachers who would be teaching the subject. The content to be covered in each of the topics was detailed on a weekly basis. Each of the topics had to be covered within a stipulated time frame followed by a cotmnon topic test that was to be administered on a particular week. In general, students were only required to learn and remember the chemical equations as well as the ionic equations, where relevant, with no specific emphasis on understanding the triplet relationship. 

From the Model of Modelling framework and knowledge of stndents difficulties in learning chemical eqnilibrinm, we developed a modelling-based teaching sequence for this theme (Ferreira Jnsti, 2005). The seqnence provides students with opportuiuties to bnild, test and rebnild models in order to explain the occurrence of a given chemical reaction, the reversibility of that chemical reaction, the establishment of a chemical eqnilibrium in the system under stndy and the behavionr of the system when the eqnilibrinm is changed. The stndents were not directly introduced... 

The system CrO / Cx20 -, provided students with a new context within which to use the model previously created for the system NO2/N2O4. From this second system students (i) acquired additional evidence about the coexistence of reactants and products in a chemical reaction and (ii) could observe what happened when the equilibrium was changed. This last set of empirical evidence was included in the teaching activities specifically to support the testing of students previous models. 

The Pieknowledge Test was administered before using the teaching unit on chemical reactions. The Preknowledge Test consisted of three tasks with subtasks checking the stndents knowledge at the micro, submicro and symbolic types of representation, whereby the maximmn score obtainable was 27. Stndents spent 25 minutes in taking the test. Details of the tasks purposes and conceptions can be obtained from the anthors. 

Case histories regarding reactive chemicals teach the importance of understanding the reactive properties of chemicals before working with them. The best source of data is the open literature. If data are not available, experimental testing is necessary. Data of special interest include decomposition temperatures, rate of reaction or activation energy, impact shock sensitivity, and flash point. 

The TSM test is a very useful construct because it asks that the examiner provide objective evidence to support his rejection. This requirement is especially important in many chemical cases where the obviousness of a chemical structure is being asserted. In order for a claim to a chemical structure or composition to be obvious, the examiner must be able to allege not only structural similarity of the chemical structure or composition but also where the prior art provides the teaching, suggestion, or motivation to make the suggested change or combination or, if not in the prior art, why one of ordinary skill would have been motivated to combine or modify the prior art in the absence of a specific teaching in the prior art itself. 

Teyler s Museum at Haarlem, The Netherlands, retains one of the most complete collections of scientific instruments amassed by an institution for the purpose of teaching and research. An earlier volume, published in 1973, elucidates the collection acquired by Martinus van Marum between 1784 and 1837. The current volume, compiled by the same author, deals with the period c. 1840 to 1915.88 A somewhat smaller proportion of the 454 entries deal with chemical apparatus compared with the earlier period, but what is to be found is not without interest, including an extensive set of equipment for testing the quality of town gas. 

We will examine whether the small mammals vulnerable to predation will avoid fresh predator odors in their home ranges. For this purpose we place in the woods live traps that are scented with odors from red fox and wolf. This experiment teaches not only basic ecology, but also the very practical skill how to test potential chemical repellents for rodent pests. 

---