Maija Ahtee

Lattice parameters and tilted octahedra in sodium–potassium niobate solid solutions

Measurements of lattice parameters and intensities of difference reflexions have been made for all compositions of Nal - xKxNbO3, both at room temperature and above. Structural models are proposed for each phase found.

Students’ understanding of chemical reaction

Students from the 7th and 8th grades at the upper stage of comprehensive school, first‐year senior secondary school, and a first‐year general chemistry course at university were asked to describe the concept of chemical reaction. Respectively, 14%, 7%, 25% and 59% of the students gave responses that included at least one of the components which point to sound understanding, namely reorganization of atoms, breaking and reformation of bonds, changes in physical or chemical properties. The students had difficulties in the usage of terms such as substance and atom. Very few of the senior secondary (6%) and university (14%) students were able to describe properly the meaning of chemical reaction. The results contribute to a clarification of why teachers experience difficulties in instructing these students in the difference between chemical and physical changes.

An International Study of Prospective Teachers’ Initial Teaching Conceptions and Concerns: the case of teaching ‘combustion’

SUMMARY An important task of science teachers should be to take pupils’ (pre)conceptions and learning difficulties into account and to negotiate about the meanings of specific concepts. In this context, teachers’ pedagogical content knowledge plays an important role. This article presents an international study of Dutch, Finnish, English and Greek pre-service teachers’ conceptions and concerns of how to teach the concept of combustion. The prospective science teachers were invited to prepare a lesson about this concept for pupils of junior secondary school level. The prospective teachers were not allowed to consult any textbook. Research data were obtained from audio-taped semi-structured interviews with the prospective teachers. In addition, their written lesson plans and their answers to an accompanying questionnaire were collected and analysed. The results reveal a number of important characteristics of prospective teachers’ views and concerns regarding the teaching of combustion. The implications of t...

Phase transitions in sodium niobate-potassium niobate solid solutions

Abstract Studies of the crystal structures of some phases in the NaxK1-xNbO3 system have been made by considering the possible tilting of the oxygen octahedra. It has been found that at room temperature the phases bear simple geometrical relationships to one another, and this has led to speculation about the high-temperature phases. Some high-temperature studies have also been carried out and are briefly discussed for the composition Na.975K.025NbO3.

Questions asked by primary student teachers about observations of a science demonstration

Teacher questioning has a central role in guiding pupils to learn to make scientific observations and inferences. We asked 110 primary student teachers to write down what kind of questions they would ask their pupils about a demonstration. Almost half of the student teachers posed questions that were either inappropriate or presupposed that the pupils would know the answer. For example, they directly asked for an explanation of the phenomenon instead of asking what inferences the pupils could make on the basis of their observations. There was a lack of questions that would draw the pupils’ attention to the variables that may cause the phenomenon to happen. Only about 15% of the student teachers formed questions such as ‘What is happening?’ or ‘How is it happening?’. All in all, primary student teachers seem to need extra practice in forming questions based on scientific observation.

Electrostatics of the ferroelectric phases of BaTiO3

Abstract Extensive theoretical calculations are reported here on the electrostatics of the three ferroelectric phases of BaTiO 3 using the static polarizable point-ion model. For each structure the following quantities have been calculated: monopole and dipole fields at ionic sites, field gradients, spontaneous polarization, high frequency dielectric constant and the Coulomb energy terms. The parameters of the model have been fitted on the basis of the experimental information on the tetragonal structure and then treated as constants for all the studied structures. The use of the experimental positional parameters of the orthorhombic structure gives such exceptional behaviour for all the calculated quantities that a redetermination of the structural parameters for this phase is suggested. Numerical study of the changes in the Coulomb energy as a function of the macroscopic depolarization potential demonstrated that the most stable state is achieved with the value zero for the potential.

HIGH-TEMPERATURE PHASES OF SODIUM NIOBATE-POTASSIUM NIOBATE SOLID SOLUTIONS

The high-temperature phases of NaNbO3-KNbO3 solid solutions consisting of 10, 20 and 35 mole % potassium were studied up to 800 K with the aid of a high-temperature furnace connected to an x-ray diffractometer. From the measurements of the lattice parameters and the intensities of some weak difference reflections as a function of temperature the tilt systems and the space groups of the several different high-temperature phases have been proposed.

Teachers’ Activities During a Mathematics Lesson as Seen in Third Graders’ Drawings

Third-graders from 19 classrooms (N = 316) were asked to draw a picture on a mathematics lesson. Based on these drawings we have produced a list which can be used to analyze how young pupils describe in their drawings their teacher’s activities during mathematics lessons. This list contains items: Teacher is giving information on mathematics, Teacher is giving instructions, Teacher is asking questions, Teacher is giving feedback, and Teacher is reflecting. In addition, the list contains information on whether the pupils have drawn the teacher at all, whether the teacher is quiet or talking, and what the teacher’s location is in the classroom. In order to show the functioning of the list we give some results of the analysis.

Developing a method to determine teachers’ and pupils’ activities during a mathematics lesson

Third-graders from nineteen classrooms (N = 316) were asked to draw a picture on a mathematics lesson. Based on these drawings we have developed a data analysing method that allows us to find out how pupils present both their teacher’s and their classmates’ activities in their drawings. Two inventories were formed that contain, respectively, teachers’ and pupils’ activities during a mathematics lesson as seen in the pupils’ drawings. The first inventory contains 14 separate items organized into six groups that contain teacher activities like asking questions and giving feedback on mathematics. Ten of the items are related to teaching and the rest contain items like keeping order in addition to the teacher’s location in the classroom. Respectively, pupils’ activities are organized into five groups that contain altogether 22 items. These contain the activities of a single pupil, and also pupil-teacher and pupil-pupil discussions on mathematics.

Pupils’ Drawings as a Research Tool in Mathematical Problem-Solving Lessons

Firstly, we describe a research project on problem-solving implemented in 2010–2013 in the Department of Teacher Education at the University of Helsinki. But we are especially concentrating on the results of one background study in the project—pupils’ drawings in a mathematics lesson. Pupils’ drawings seem to be a powerful method to gather information from small children. With the aid of drawings, one may investigate different topics in children’s thinking. Here, we focus on pupils’ and teachers’ communication, the emotional atmosphere of the class and the types of work used in class. The drawing studies offer three different channels to pupils’ conceptions in problem-solving.