# A Virtual Experiment for Learning the Principle of Daniell Cell Based on Augmented Reality
## 1 Introduction
### Virtual Daniell Cell Experiment  
In high school chemistry, \"acid and alkali\" and \"redox\" are interesting but difficult learning topics. Researchers suggested that specific methods should be used to help students understand the basic concepts [41]. The basic knowledge of the above learning topics involves electrochemistry, a branch of physical chemistry that studies the relationship between electricity and an identifiable chemical change. In electrochemistry, electricity is a measurable and quantitative phenomenon, and it is considered an outcome of a particular chemical reaction or vice versa [42]. The reaction of the Daniell cell experiment involves electric charges moving between electrodes and an electrolyte as well as the ionic species in a solution. A chemical reaction is called an electrochemical reaction if it is caused by an externally supplied current, as in electrolysis, or if an electric current is produced by a chemical reaction, as in a battery. Chemical reactions are called oxidation-reduction (redox) reactions where electrons are transferred between atoms and/or molecules. In general, electrochemistry describes the overall reactions when individual redox reactions are separate but connected by an external electric circuit and an intervening electrolyte, as in the Daniell cell. The objective of this study is to develop a virtual experiment for learning how to design a Daniell cell to generate electricity. When conducting the experiment, the copper strip (placed in the solution of copper sulfate) is the anode and the zinc strip (placed in the solution of zinc sulfate) is the cathode. The salt bridge is used as a conducting circuit such that electrons can flow through the galvanometer for detecting the current produced by the redox reaction. Students can explore autonomously during the virtual experiment, from selecting the experimental equipment and materials to connecting the Daniell cell with the galvanometer. They can observe if the pointer on the galvanometer moves to determine if there is current generated by the Daniell cell, and measure whether the mass of the zinc strip and the copper strip has changed to tell if it is an oxidation or a reduction reaction. The design of virtual experiment is based on the theoretical framework of [PERSON]'s triangle and it combines different levels (macroscopic, submicroscopic, and symbolic) of representation: (1) Macroscopic: students can conduct the virtual experiment by selecting the required equipment to set up the experimental environment and observe the macroscopic results, (2) Submicroscopic: students can see the change of molecular structures and movement of electrons and ions during the redox reaction to understand the related concepts and knowledge, and (3) Symbolic: the chemical symbols and structural formulas are shown on the AR cards and in the virtual scene to help students understand the principles of chemical reactions. To solve the dilemma faced by high school chemistry teachers, this study combined the AR and VR technologies with inquiry-based learning to develop a virtual experiment where students can see the change of molecular structures and movement of electrons and ions during the redox reaction to understand the principle of Daniell cells. Students can conduct the virtual experiment using a mobile device by selecting the required equipment from a deck of AR cards to set up the experimental environment. They can also obtain the important concepts and knowledge through the explorative process and the guidance of learning scaffolds (Figure 2). The system provides appropriate hints to help students in the experimental process for them to construct scientific concepts along the conceptual framework. It is different from instructing them to conduct the real experiment by following the experimental procedure step by step.