Teachers' Mole Concept Pedagogical Content Knowledge: Developing the Model for the mole Concept Content Representations Framework

Teaching and learning difficulties have been documented in numerous studies in literature. However not much has been done to develop a model of the mole concept Content Representations (CoRes) framework to simultaneously enhance teachers' mole concept Content Knowledge (CK) and Pedagogical Content Knowledge (PCK). Thus the study sought to fill up this gap in literature by developing the model of the mole concept CoRes framework through the assessment of teachers’ mole concept PCK. The study was conducted in 6 selected secondary schools in Kitwe district in the Copperbelt province of Zambia with a study sample of 30 grade 11 chemistry teachers. The data was collected using the questionnaire, lesson observations, Content Representations (CoRes) framework, and focus group discussion. The data was analysed by categorising it into themes captured by the conceptual framework of the study.  The findings of the study revealed that teachers’ mole concept PCK was weak and this was largely attributed to their conceptual limitations exhibited in their mole concept CK.  Their presentation of the topic was characterised by algorithmic approaches, semantics mistakes and didactic difficulties. The developed mole concept CoRes framework focuses on addressing the conceptual and didactic limitations identified in literature and by the study. Keywords: Mole concept, content knowledge, Pedagogical Content Knowledge DOI: 10.7176/JEP/10-8-08 Publication date:March 31st 201

Fabrication and Characterization of Cobalt Pigmented Anodized Zinc for Photocatalytic Application

ZnO is an n-type oxide semiconductor with a direct wide band gap greater than 3 eV. Like any other semiconductor, the optical and electrical characteristics can be influenced by doping or adjusting process conditions which broaden its applications. In this work, varying amounts of Cobalt (0.01g-0.04g) were electrodeposited on anodized Zinc thin films (ZnO) followed by heat treatment to about 2500C. Optical characterization was performed in the range 300-2500 nm to obtain reflectance data which aided in defining the absorption coefficient and band gap of the films. Photocatalytic activity of the films was explored in Methylene Blue solution degradation under UV light irradiation. Analyzed data revealed a band gap shift to the red, i.e. from 3.34 eV to 3.10 eV for pure ZnO and 0.04g-Cobalt pigmented ZnO thin films respectively. Moreover, absorption coefficient increased with pigmentation attributed to the band shrinkage effect which elucidates that ZnO:Co thin films serve as good candidates for application in photocatalysis. All the fabricated films were photocatalytic but ZnO thin films containing 0.02g of Cobalt was the most photocatalytic

Optical characterization of photocatalytic copper doped thin films of anodized titanium

Titanium oxide is used in a myriad of applications such as in capacitors, insulation paints among others. It is a prime candidate for water splitting due to its photocatalytic properties. In this work, undoped TiO _2 thin films were prepared by anodizing titanium foils cut into pieces measuring 60 mm by 20 mm. The specimens were anodized in an electrolyte consisting of 0.5 M H _2 SO _4 and 0.075% wt HF at room temperature. The anodizing voltages ranged from 50 V to 100 V. Anion doping of copper in as anodized TiO _2 was done electrochemically. The as anodized Ti foils were dipped in a 1 M Cu _2 SO _4 solution. All samples were annealed at 450 °C for 3 h. Near-normal total reflectance was measured on as anodized and copper pigmented samples in the solar (300–2500 nm) wavelength range. Spectrophotometric reflectance data was analyzed to obtain the absorption coefficient and using the same to determine the band gap of the films. It was noted that the films exhibited reduced solar integrated reflectance for TiO _2 samples prepared at lower anodic voltages of 50, 60 and 70 V. The copper pigmented, and annealed, TiO _2 samples exhibited both direct and indirect energy band gaps in the ranges, 3.38–3.86 and 2.50–2.74, respectively. Further, annealing and copper doping of the films lead to increased absorption. The photocatalytic activity of the films was assessed by measuring the rate of degradation of 10ppm methylene blue in UV light source. Copper doped TiO _2 exhibited enhanced photocatalytic performance in compared to pure TiO _2 . An increase in the anodization voltage caused subsequent increase in photocatalytic activity of films with 70 V as the optimum voltage above which photo degradation of methylene blue decreased