How much instructional assistance to provide to students as they learn, and what kind of assistance to provide, is a much-debated problem in research on learning and instruction. This study presents two multi-session classroom experiments in the domain of chemistry, comparing the effectiveness and efficiency of three highassistance (worked examples, tutored problems, and erroneous examples) and one low-assistance (untutored problem solving) instructional approach, with error feedback consisting of either elaborate worked examples (Experiment 1) or basic correctness feedback (Experiment 2). Neither experiment showed differences in learning outcomes among conditions, but both showed clear efficiency benefits of worked example study: equal levels of test performance were achieved with significantly less investment of time and effort during learning. Interestingly for both theory and practice, the time efficiency benefit was very substantial: worked example study required 46-68% less time in Experiment 1 and 48-69% in Experiment 2 than the other instructional approaches.

A collection of online activities emphasizes the design and interpretation of experiments. C hemistry concepts are abstract and can be diffi cult to attach to real-world experiences. For this reason, highschool and college chemistry courses focus on a concrete set of problem types that have become canonized in textbooks and standard exams. These problem types emphasize development of the core notational and computational tools of chemistry. Even though these tools may form the underlying procedural knowledge base from which the "real stuff " can be approached, when taught out of contexts that show their utility or that draw connections to core ideas of science, they can appear as a disconnected bag of tricks (1).The ChemCollective (www.chemcollective. org) is a digital library of online activities for general chemistry instruction that engages students in more authentic problem-solving activities than those found in most textbooks. Our goal is to create activities that allow students to use their chemistry knowledge in ways that resemble the activities of practicing chemists. Our guiding hypothesis is that better conceptual understanding is obtained if algebraic computations are complemented with design and interpretation of experiments. This is achieved through the ChemCollective "Virtual Lab," which allows students to design and carry out their own experiments while experiencing representations of chemistry that go beyond what is possible in a physical laboratory. The goal is not to replace, or even to emulate, the physical laboratory, but to supplement textbook problem-solving by connecting abstract concepts to experiments and real-world applications. We believe that such authentic activities may improve learning and may better help to bring the essence of science into the introductory chemistry classroom.In the virtual lab (see the fi gure, right), the panel on the left is a customizable stockroom of chemical reagents, which may include common reagents or fi ctional materials that have properties specifi ed by the instructor. The middle work space provides an area for performing experiments. The right panel provides multiple representations of the contents of the selected solution, including the temperature and pH, and a list of chemical species with amounts shown as moles, grams, or molar concentrations. These quantities are the players in the computational procedures of the course, and so this panel provides an explicit link between the paper-and-pencil calculations of the traditional course and the chemical experiments the student performs on the workbench.The virtual lab supports new forms of problem-solving. Consider how the concept of limiting reagents in a reaction is usually taught. A student's practice with this concept typically centers around learning a standard computational procedure for predicting the fi nal amount of chemical reagents, given the initial amounts. Our "unknown reaction" virtual lab activity provides a different mode of practice. Students are given four unknown chemicals (A, B, C...

A comparison of the central, valued activities of the field of chemistry with the curricula presented in introductory texts reveals a disconnect between what is taught in school and what the field actually encompasses. The comparison was made by utilizing a conceptual framework of the domain developed around the three main activities of chemists: explaining phenomena, analyzing matter, and synthesizing new substances. Underlying these activities is the toolbox of basic notational and quantitative schemes. The elements of the comparison were textbooks as used and Nobel Prizes in chemistry, chemistry-related articles from a newspaper, and chemistry-related articles from a science magazine. These were located within the framework. The Nobel Prizes and news articles were evenly distributed among the three main activities of chemists; the textbook objectives focus almost exclusively on explaining phenomena and the toolbox, with the exception of one text, Chemistry in the Community. This misalignment suggests that traditional introductory courses may not meet the basic goals of scientific literacy if scientific literacy is supposed to reflect the organization of a field. It is suggested that by modeling instruction on the specific activities of chemists, with the necessary tools developed as needed, teachers could help students comprehend the authentic nature of the discipline as well as help them construct meaningful links within their knowledge base.

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Abstract. How much help helps in discovery learning? This question is one instance of the assistance dilemma, an important issue in the learning sciences and educational technology research. To explore this question, we conducted a study involving 87 college students solving problems in a virtual chemistry laboratory (VLab), testing three points along an assistance continuum: (1) a minimal assistance, inquiry-learning approach, in which students used the VLab with no hints and minimal feedback; (2) a mid-level assistance, tutored approach, in which students received intelligent tutoring hints and feedback while using the VLab (i.e., help given on request and feedback on incorrect steps); and (3) a high assistance, direct-instruction approach, in which students were coaxed to follow a specific set of steps in the VLab. Although there was no difference in learning results between conditions on near transfer posttest questions, students in the tutored condition did significantly better on conceptual posttest questions than students in the other two conditions. Furthermore, the more advanced students in the tutored condition, those who performed better on a pretest, did significantly better on the conceptual posttest than their counterparts in the other two conditions. Thus, it appears that students in the tutored condition had just the right amount of assistance, and that the better students in that condition used their superior metacognitive skills and/or motivation to decide when to use the available assistance to their best advantage.