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The purpose of this research was to investigate an efficient method to assess year 8 (age 13-14) students' conceptual understanding of heat and temperature concepts. Two different types of instruments were used in this study: Type 1, consisting of multiple-choice items with open-ended justifications; and Type 2, consisting of two-tier multiple-choice items. Each of the instruments was administered to two separate cohorts of 173 and 143 year 8 students of similar achievement. The findings indicated that the students were better able to show their understanding in the two-tier multiple-choice items. Hence, based on this investigation, two-tier multiple-choice items may be more suitable for evaluating year 8 students' understanding of science concepts.

This study focuses on elucidating and explaining reasons for the stability of and interrelationships between students' conceptions about "Light Propagation" and "Visibility of Objects" using contextualized questions across 3 years of secondary schooling from Years 7 to 9. In a large-scale quantitative study involving 1,233 Korean students and 1,149 Singaporean students, data were analyzed from responses to the "Light Propagation Diagnostic Instrument" consisting of four pairs of items, each of which evaluated the same concept in two different problem situations. Findings show that only about 10-45 % of students could apply their conceptions of basic optics in contextualized problem situations giving rise to both stable and unstable alternative conceptions. Students' understanding of "Light Propagation" concepts compared with "Visibility of Objects" concepts was more stable in different problem situations. The concepts of "Light Propagation" and "Visibility of Objects" were only moderately correlated. School grade was not a strong predictive variable, but students' school achievement correlated strongly with their conceptual understanding in optics. The teaching and learning approach and education systems in the two countries may have had some influence on students' conceptual understanding.

An instructional program using four simulation applets was used to facilitate understanding of gas and liquid pressure concepts among twenty-two students in a Year 9 class from an independent secondary school in Singapore. A comparison group consisting of twenty-two students was taught using traditional didactic, chalk-and-talk instruction. Administration of a gas and liquid pressure conceptual test comprising ten multiple-choice items in a pretest-posttest design indicated significant improvement in understanding using the simulation applets compared to the didactic instruction. A seven-item attitudes questionnaire indicated that the students generally found the animation applets interesting and helpful in their physics lessons. (Contains 4 figures and 2 tables.)

Background: The Trends in International Mathematics and Science Study (TIMSS) assesses the quality of the teaching and learning of science and mathematics among Grades 4 and 8 students across participating countries. Purpose: This study explored the relationship between positive affect towards science and mathematics and achievement in science and mathematics among Malaysian and Singaporean Grade 8 students. Sample: In total, 4466 Malaysia students and 4599 Singaporean students from Grade 8 who participated in TIMSS 2007 were involved in this study. Design and method: Students' achievement scores on eight items in the survey instrument that were reported in TIMSS 2007 were used as the dependent variable in the analysis. Students' scores on four items in the TIMSS 2007 survey instrument pertaining to students' affect towards science and mathematics together with students' gender, language spoken at home and parental education were used as the independent variables. Results: Positive affect towards science and mathematics indicated statistically significant predictive effects on achievement in the two subjects for both Malaysian and Singaporean Grade 8 students. There were statistically significant predictive effects on mathematics achievement for the students' gender, language spoken at home and parental education for both Malaysian and Singaporean students, with R[squared] = 0.18 and 0.21, respectively. However, only parental education showed statistically significant predictive effects on science achievement for both countries. For Singapore, language spoken at home also demonstrated statistically significant predictive effects on science achievement, whereas gender did not. For Malaysia, neither gender nor language spoken at home had statistically significant predictive effects on science achievement. Conclusions: It is important for educators to consider implementing self-concept enhancement intervention programmes by incorporating "affect" components of academic self-concept in order to develop students' talents and promote academic excellence in science and mathematics. (Contains 4 tables and 1 figure.)

This study involved the evaluation of the efficacy of a planned instructional program to facilitate understanding of the macroscopic, submicroscopic and symbolic representational systems when describing and explaining chemical reactions by sixty-five Grade 9 students in a Singapore secondary school. A two-tier multiple-choice diagnostic instrument consisting of fifteen items was administered after nine months of instruction. Analysis of the students' performance on the diagnostic test, showed improved understanding of the use of multiple representations compared to that of seventy-six students of similar achieving ability in the prescribed program of instruction. (Contains 1 table and 3 figures.)

This paper reports on the understanding of three key conceptual categories relating to the kinetic particle theory: (1) intermolecular spacing in solids, liquids and gases, (2) changes of state and intermolecular forces and (3) diffusion in liquids and gases, amongst 148 high school students from Brunei, Australia, Hong Kong and Singapore using 11 multiple-choice items that required students to provide explanations for their selection of particular responses to the items. Students' responses to the items revealed limited understanding of the particle theory concepts, with nine alternative conceptions held by more than 10% of various samples of students. Also, 40.5-78.4% of all students indicated consistent understanding relating to the three conceptual categories based on their responses to the 11 items. However, when their explanations were taken into account, very few students displayed consistent understanding of the related concepts.

In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four multiple-choice items were developed to determine the understanding of 217 pre-service science teachers of the kinetics of acid reactions that are taught at the Grade 9 to 10 levels in Singapore schools. Each of four items compared two different acid reactions under similar conditions, and respondents were required to select the best graphical representation for the two reactions. Respondents were also required to provide reasons to explain their particular selection for each item. In addition, one item on the dissociation of sulfuric acid and two items involving excess/limiting reagents were also included to provide additional data on the pre-service teachers' understanding of these concepts that were assessed in the four items on kinetics of acid reactions. The results showed that the pre-service teachers had difficulties in explaining the properties of different common acids, including the dissociation of the acids and how these affect the rates of the different acid reactions. This study highlights the importance of determining pre-service teachers' understanding of the concepts that they will be teaching with a view to addressing areas of difficulty, as these will have consequences on their future students' learning. (Contains 4 tables and 14 figures.)

An alternative program of instruction was implemented with 33 high-achieving Grade 9 students (15-16 years old) in Singapore that overtly focused on the use of macroscopic, submicroscopic, and symbolic representations to describe and explain the changes that occurred during the burning of metals, reactions of dilute acids, ionic precipitations, and metal ion displacement reactions. Students' understandings of the use of multiple levels of representation were evaluated at the end of nine months of instruction using a previously developed 15-item, two-tier, multiple-choice diagnostic instrument. In several instances the students displayed much better understanding of the three systems of representation than 44 students from another higher-achieving Grade 9 class who were taught with the regular instructional program that did not emphasize use of multiple levels of representation. Comparison of the mean diagnostic test scores of students from the two classes indicated that the high-achieving class in the treatment group that experienced the alternative program of instruction performed significantly better than the higher-achieving class from the comparison group that experienced the regular program of instruction, further validating the efficacy of the alternative instructional program. (Contains 1 table and 1 figure.)

A thorough understanding of chemical bonding requires familiarity with the particulate nature of matter. In this study, a two-tier multiple-choice diagnostic instrument consisting of ten items (five items involving each of the two concepts) was developed to assess students' understanding of the particulate nature of matter and chemical bonding so as to identify possible associations between students' understandings of the two concepts. The instrument was administered to 260 Grades 9 and 10 students (15-16 years old) from a secondary school in Singapore. Analysis of students' responses revealed several alternative conceptions about the two concepts. In addition, analysis of six pairs of items suggested that students' limited understanding of the particulate nature of matter influenced their understanding of chemical bonding. The findings provide useful information for challenging students' alternative conceptions about the particulate nature of matter during classroom instruction in order to enable them to achieve better understanding of chemical bonding. (Contains 3 figures and 6 tables.)

Students are generally known to memorise and regurgitate chemical equations without sufficient understanding of the changes that occur at the particulate level. In addition, they often fail to recognise the significance of the symbols and formulas that are used to represent chemical reactions. This article describes an evaluation of the ability of 65 Grade 9 students (15-16 years old) from a Singapore secondary school to describe and explain seven types of chemical reactions using macroscopic, submicroscopic and symbolic representations. The study was conducted over nine months using a supplementary teaching program with particular emphasis on the use of multiple levels of representation to describe and explain chemical reactions. Students' proficiency in the use of multiple levels of representation was assessed at the end of the course using a two-tier multiple-choice diagnostic instrument that was previously developed by the authors. In order to evaluate the efficacy of the instructional program, the instrument was also administered to another group of 76 students who were not involved in the supplementary instructional program. The efficacy of the program was evident from the significantly improved scores on the diagnostic instrument of the former group of students. In addition, several student conceptions in the use of multiple levels of representation were identified that could assist teachers in their planning and implementation of classroom instruction.

Uses a two-tier, multiple-choice diagnostic instrument to determine (n=915) grade 10 students' understanding of the acid, base, and salt reactions involved in basic qualitative analysis. Reports that many students did not understand the formation of precipitates and the complex salts, acid/salt-base reactions, and thermal decomposition involved in qualitative analysis. (Contains 16 references.) (Author/YDS)

Grade 10 students in Singapore find qualitative analysis one of the more difficult topics in their external examinations. Fifty-one grade 10 students from three schools were interviewed to investigate their perceptions about learning qualitative analysis. The results showed that students found qualitative analysis tedious and difficult to understand, and found the practical sessions unrelated to what they learned in class. (Author/MM)

Nitrogen dynamics at the sediment–water interface were examined in a tropical reservoir, Upper Peirce Reservoir, Singapore to provide information on the relative importance of each process and evaluated the spatial differences of nitrogen dynamics. The intact sediment cores were collected from three locations with different depths and distances to the artificial aeration system. The flow-through system combined with the isotope pairing technique was applied to estimate the nitrogen fluxes, potential denitrification rates and anammox rates. A mass balance model was developed and calibrated with the experimental results, and calculated mineralization, nitrification and dissimilatory nitrate reduction process rates. The sediment had a strong mineralization rate (13.39 mmol m −2 d −1 ) at shallow section, thus, had obvious NH 4 -N fluxes (17.61 mmol m −2 d −1 ). The total N 2 removal rates through denitrification and anammox processes ranged from 0.08 to 0.28 mmol m −2 d −1 , relatively lower than that in estuaries and coastal systems. Denitrification was performed as the main loss pathway, dominating up to 98% of total N 2 removal rates. The coupled nitrification–denitrification ( D n ) was dominant as compared to denitrification that happened from water column nitrate ( D w ). Nitrification and N 2 removal rates increased with water column depth. The artificial aeration around the deeper section might have contributed to the bacteria activities, and thus might stimulate high microbial processes converting NH 4 -N to NO 3 -N and bioactive nitrogen to N 2 gas. The discovery of nitrogen transformation pathways in tropical freshwater systems are proposed to be incorporated into future conceptual models of global nitrogen cycles. [ABSTRACT FROM AUTHOR]

Abstract: Atmospheric nutrients have recently gained increased attention as significant additional sources of new nitrogen (N) and phosphorus (P) loading to aquatic ecosystems. The levels of nutrients (NO3 −–N, NH4 +–N, ON, DIP and OP) in aerosols and rainwater were measured and their respective deposition fluxes were estimated in the Marina catchment area, Singapore, from April 2007 to March 2008. During the study period, the mean atmospheric dry particulate fluxes (mgm−2 month−1) were 21.64±13.56, 2.95±1.73, 24.21±9.59, 4.48±1.74 and 7.19±2.83 for NO3 −–N, NH4 +–N, ON, DIP and OP, respectively. In addition, the mean wet deposition fluxes (mgm−2 month−1) were 59.60±45.29, 30.39±12.99, 39.03±20.70, 1.79±1.03 and 2.46±1.29 for NO3 −–N, NH4 +–N, ON, DIP and OP, respectively. Wet deposition made a larger contribution to total fluxes than dry deposition for N species especially NO3 − and NH4 +, but P species showed the opposite trend. Both TN and TP showed different seasonal variations with peak wet deposition fluxes in Dec 2007 and Jan 2008 as compared to dry deposition fluxes which peaked during the inter-monsoon (IM) period. Other than the local emissions, air mass backward trajectory analysis indicated that the atmospheric nutrient concentration may be affected by transboundary transport of nutrients from regional sources during different monsoon seasons. Statistical correlation analysis showed that the deposition fluxes were associated with meteorological factors. In addition, the N:P ratio in annual total (dry particulate+wet) atmospheric deposition flux in this study was 10.5, implying that the aquatic ecosystems in Singapore, fed principally by atmospheric nutrients, may tend toward N-limitation. [Copyright &y& Elsevier]

Most students' introduction to qualitative analysis (QA) is in general chemistry courses at college or university in the United States of America, or as part of analytical chemistry courses for chemistry majors in Australian universities. However, in Singapore, students' first experience with QA is in grade 10 even though the topic is considered conceptually difficult to understand and there is inadequate time for comprehensive experimental work. In Singapore, high achieving grade 10 students take the national General Certificate of Education Ordinary Level chemistry examination that includes a practical examination; inorganic chemistry QA is usually one of the two experiments that students have to perform in the practical examination. Students perform a series of procedures using chemicals, apparatus, and appropriate techniques in QA experiments observe and record what happens, and make inferences based on their observations.

The First-Line Erbitux in Lung Cancer (FLEX) trial showed that the addition of cetuximab to chemotherapy followed by weekly cetuximab maintenance significantly improved survival in the first-line treatment of advanced non-small cell lung cancer (NSCLC). The phase IIIb NSCLC Erbitux Trial (NEXT) trial (NCT00820755) investigated the efficacy and safety of weekly and every 2 weeks cetuximab maintenance therapy in this setting. Patients were treated with platinum-based chemotherapy plus cetuximab, and those progression-free after four to six cycles were randomized to every 2 weeks (500 mg/m(2)) or weekly (250 mg/m(2)) cetuximab maintenance. Randomization was stratified for tumor histology and response status. The primary endpoint for a regimen would be reached if the lower boundary of the 95 % confidence interval (CI) for the 1-year survival rate exceeded 55 %. A planned 480 patients were to be randomized. However, enrollment was curtailed following a negative opinion from the European Medicines Agency with regard to the use of cetuximab in this setting. After combination therapy, 311/583 (53.3 %) patients without progression were randomized to maintenance therapy: 157 to every 2 weeks cetuximab and 154 to weekly cetuximab. Baseline characteristics were balanced between these groups and exposure to cetuximab was similar. The 1-year survival rate was 62.8 % (95 % CI, 54.7-70.0) for every 2 weeks cetuximab and 64.4 % (95 % CI, 56.2-71.4) for weekly cetuximab. Safety profiles were similar, manageable, and in line with expectations. Therefore, in patients with advanced NSCLC who were progression-free after four to six cycles of first-line chemotherapy plus cetuximab, weekly and every 2 weeks cetuximab maintenance therapy were associated with similar survival outcomes.