The main purpose of this study was to compare the effectiveness of 5E learning cycle model based on constructivist theory approach over traditionally designed chemistry instruction on ninth grade students&rsquo / understanding of acid-base concepts. Sixty tenth grade students from two classes of a chemistry course taught by the same teacher in Ankara Atat&uuml / rk Anatolian High School 2004-2005 spring semester were enrolled in the study. The classes were randomly assigned as control and experimental groups. Students in the control group were instructed by traditionally designed chemistry instruction whereas students in the experimental group were taught by the instruction based on constructivist approach. Acid-Base Concepts Achievement Test was administered to both groups as a pre-test and post-test in order to assess their understanding of concepts related to acid-base. Students were also given Attitude Scale Toward Chemistry as a School Subject at the beginning and end of the study to determine their attitudes and Science Process Skill Test at the beginning of the study to measure their science process skills. The hypotheses were tested by using analysis of covariance (ANCOVA) and t-test. The results indicated that instruction based on constructivist approach caused significantly better acquisition of scientific conceptions related to acid-base and produced significantly higher positive attitudes toward chemistry as a school subject than the traditionally designed chemistry instruction. In addition, science process skill was a strong predictor in understanding the concepts related to acid-base.

The effect of case based learning on 10th grade students&rsquo / academic achievement in the unit of human reproductive system and their perceived motivation (Intrinsic Goal Orientation, Extrinsic Goal Orientation and Task Value) was investigated in this study. The study was conducted during 2007-2008 spring semester in a private high school in Ankara, Turkey. A total of 80 (48 males and 32 females) tenth grade students from four biology classes of two teachers were involved in the study. One class of each individual teacher was assigned as control group and the other class of the same teacher was assigned as experimental group to sustain randomization. Two of the classes assigned as experimental group were instructed with case based learning, while two classes of the control group were received traditionally designed biology instruction. In the experimental group, two cases that are divided into several parts were assigned in an interrupted manner. Students learned the human reproductive system via cases in experimental group without any additional method. The cases include incomplete data and students were needed to search for and discuss to answer the questions posed in the cases and by themselves and to complete the data. When the students completed a part of the case, next part was distributed. While dealing with the dilemma presented in cases, students did independent study as well as group work. In the control group, instruction was based on teacher explanations and web based notes prepared by the biology department of the high school. Human Reproductive System Achievement Test, Motivated Strategies for Learning Questionnaire were administered as pre-test and post-test to the students in both groups to measure the students&rsquo / academic achievement in the unit of human reproductive system / and their perceived motivation / specifically, task value, intrinsic goal orientation, and extrinsic goal orientation. Multivariate Analysis of Variance (MANOVA) was used to investigate the effect of case based learning on the students&rsquo / academic achievement in the unit of human reproductive system and their perceived motivation. Results revealed that case based learning improved students&rsquo / academic achievement and task value.

In this thesis work, importance of radome structures for antenna systems is emphasized. Structural and electromagnetic requirements of various types of radome structures are analyzed and specific properties are given. Electromagnetic scattering analysis of sandwich type radome seams has been done. Total antenna system far electromagnetic field expression, which is the combination of original antenna far electromagnetic field and the scattered electromagnetic field of the framework of the sandwich radome structure has been found and simulated. To enhance electromagnetic transparency of sandwich type radomes two sandwich radome design methods are proposed which are expressed as Geometrical Randomization and Tuning the Seams. Electromagnetic scattering level minimizations advanced by these design methods are presented with related simulations.

The main purpose of this study was to investigate the effects of conceptual change oriented instruction accompanied with analogies on eight grade students&rsquo / understanding of chemical bonding concepts. In addition, the effect of instruction on students&rsquo / attitude toward science as a school subject and the effect of gender difference on understanding of chemical bonding concepts were investigated. Fifty eight-grade students from two classes of a science course taught by the same teacher in B&uuml / y&uuml / kel&ccedil / i Nazim Belger Primary School in the 2010-2011 spring semesters participated in the study. The study included two groups which were selected randomly throughout three classes. One of the groups was defined as control group in which students were instructed by traditionally designed science instruction, while other group was defined as experimental group in which students were instructed by conceptual change texts oriented instruction accompanied with analogies. Chemical Bonding Concept Pre-Test was administered to both groups as a pre-test and Chemical Bonding Concept Post-Test was administered to both groups as a post-test in order to assess their understanding of concepts related to chemical bonding. Students were also given Attitude Scale Towards Science as a School Subject at the beginning and end of the study to determine their attitudes and Science Process Skill Test was used at the beginning of the study to measure their science process skills. The hypotheses were tested by using analysis of covariance (ANCOVA) and two-way analysis of variance (ANOVA). The results indicated that instruction based on constructivist approach caused a significantly better acquisition of scientific conceptions related to chemical bonding and produced significantly higher positive attitudes toward science as a school subject than the traditionally designed science instruction. Also, science process skill was a strong predictor in understanding the concepts related to chemical bonding. On the other hand, no significant effect of gender difference on understanding the concepts about chemical bonding and students&rsquo / attitudes toward science as a school subject was found.

Structural studies of peptides has relevance for various applications, like, in de novo design of proteins, in designing better catalysts for organic synthesis, in structure based drug design, in the design and construction of synthetic protein mimics and in building novel materials via supramolecular self assembly. Crystal structure determination of peptides is expected to provide information about their static structure, mode of aggregation, solvation and hydrogen bond interactions of the sequences in the solid state. Comparison and analysis of the related structures from the database analysis could provide information about sequence dependent conformational features, which eventually would act as precursor for de novo protein design. Self assembling processes are common throughout nature and technology. Living cells self assemble, and understanding life will therefore require an understanding of self assembly. Supramolecular chemistry has become an area of intense research, partly inspired by biological ensembles in nature, such as collagen and enzymes or protein assemblies in general. Understanding, inducing, and directing such self assembling processes are key to unraveling the progressive emergence of complex matter. Most of the drugs available today have a broad spectrum of action in that they can act on more than one receptor and the mechanism of action of these drugs are poorly understood. Homology modeling of receptors and docking studies with drug molecules (both peptides and non-peptides) would result in a better understanding of the mechanism of drug-receptor binding thus resulting in the design of more specific and effective drugs. This thesis reports the results of X-ray crystallographic studies of ten molecules listed below (Ter: terephthalic acid) and the molecular model of cholecystokinin type 1 receptor (CCK1R). The abbreviations used for the sequences are given in parenthesis. Boc-Gly-Dpg-Gly-Leu-OMe (GDGL), C24H44N4O7 Boc-Val-Ala-Leu-Dpg-Val-Ala-Leu-Val-Ala-Leu-Dpg-Val-Ala-Leu-OMe (VAL14), C78H14 2N14O17 MeO-Leu-Ter-Leu-OMe (LTeL), C22H32N2O6 MeO-DLeu-Ter-DLeu-OMe (DLTeDL), C22H32N2O6 MeO-Ile-Ter-Ile-OMe (ITeI), C22H32N2O6 MeO-Aib-Ter-Aib-OMe (UTeU), C18H24N2O6 Tyr-Aib-Tyr-Val (YUYV), C27H36N4O7 Tyr-Aib-Ala (YUA), C16H23N3O5 Z-Gly-Gly-Val (ZGGV), C17 H23 N3 O6 DL-4-benzamido-N, N-dipropylglutaramic acid (proglumide), C18 H26 N2 O4 Results from the Dpg containing peptide sequences helped to further the understanding of conformational preferences of this residue. The crystallographic studies on the peptide sequence, which forms a supramolecular triple helix and four pseudopeptide sequences, which adopt supramolecular ladder conformations has provided substantial information on the role of non covalent interactions in supramolecular self assembly. Crystal structure of a Gly-Gly containing tripeptide and database analysis has provided insights into the conformations adopted by this segment in peptides and proteins. The docking of the crystal structure of proglumide, an antagonist of CCK1R has led to the understanding of the mechanism of its interaction with CCK1R.

Peptides have assumed considerable importance in pharmaceutical industry and vaccine research. Understanding the structural features of these peptide molecules can be effective not only in mimicking natural proteins but also in the design of new biomaterials. Polypeptide sequences consisting of twenty genetically coded amino acids possess structural flexibility, which makes the predictions difficult. However, the introduction of non-protein amino acids into the peptide chain restricts the available range of backbone conformations and acts as stereochemical directors of polypeptide chain folding. Such conformationally rigid residues allow the formation of well defined structures like helices, strands etc, which further assemble into super secondary structural motifs by flexible linkages. Crystal structure determination of the oligopeptides by X-ray diffraction gives insight into the specific conformational states, modes of aggregation, hydrogen bond interactions, solvation of peptides and various weakly polar interactions involving the side chains of aromatic residues (Phe, Trp and Tyr). In β-, γ- and higher ω-amino acids, due to the insertion of one or more methylene groups between the N- and Cα-atoms into the peptide backbone the accessible conformational space is greater than the α-amino acids. The β-, γ-, δ-…. amino acid residues belong to the family of ω-amino acids. Extensive research in the field of β-peptides, which have been experimentally verified or theoretically postulated, has assigned several helices, turns and sheets. The use of ω-amino acid residues in conjunction with α-residues permits systematic exploration of the effects of introducing additional backbone atoms into well-characterized α-peptide structures. The observation of new families of hydrogen bonded motifs in the hybrid peptides containing α- and ω-amino acids are the recent interest in this regard. This thesis reports results of X-ray crystallographic studies of eighteen designed peptides and four protected ω-amino acids listed below. Within brackets are given the abbreviations used for the sequences (Symbol U represents Aib). The ω-amino acids reported in this thesis are: (S)-β3-HAla (β3-homoalanine), (R)-β3-HVal, (S)-β3-HVal (β3-homovaline), (S)-β3-HPhe (β3-homophenylalanine), (S)-β3-HPro (β3-homoproline), βGly (β-homoglycine), γAbu (gamma aminobutyric acid) and δAva (delta aminovaleric acid). 1. Boc-Leu-Trp-Val-OMe (LWV), C28H42N4O6 2. Ac-Leu-Trp-Val-OMe (Space group P21) (LWV1), C25H36N4O5 3. Ac-Leu-Trp-Val-OMe (Space group P212121) (LWV2), C25H36N4O5 4. Boc-Leu-Phe-Val-OMe (LFV), C26H41N3O6 5. Ac-Leu-Phe-Val-OMe (LFV1), C23H35N3O5 6. Boc-Ala-Aib-Leu-Trp-Val-OMe (AULWV), C35H54N6O8 7. Boc-Trp-Trp-OMe (WW), C28H32N4O5 8. Boc-Trp-Aib-Gly-Trp-OMe. (WUGW), C34H42N6O7 9. Boc-Leu-Trp-Val-Ala-Aib-Leu-Trp-Val-OMe (H8AU), C57H84N10O11 10. Boc-(S)-β3-HAla-NHMe (BANH), C10H20N2O3 11. Boc-(R)-β3-HVal-NHMe (BVNH), C12H24N2O3 12. Boc-(S)-β3-HPhe-NHMe (BFNH), C16H24N2O3 13. Boc-(R)-β3-HVal-(R)-β3-HVal-OMe (BVBV), C18H34N2O5 14. Boc-(R)-β3-HVal-(S)-β3-HVal-OMe (LVDV), C18H34N2O5 15. Boc-(S)-β3-HPro-OH (BPOH), C11H19N1O4 16. Boc-Leu-Phe-Val-Aib-(S)-β3-HPhe-Leu-Phe-Val-OMe (UBF8), C60H88N8O11 17. Piv-Pro-Gly-NHMe (PA1), C13H23N3O3 18. Piv-Pro-βGly-NHMe (PB1), C14H25N3O3 19. Piv-Pro-βGly-OMe (PBO), C14H24N2O4 20. Piv-Pro-δAva-OMe (PDAVA), C16H28N2O4 21. Boc-Pro-γAbu-OH (BGABU), C14H24N2O5 22. Boc-Aib-γAbu-OH (UG), C13H24N2O5 23. Boc-Aib-γAbu-Aib-OMe (UGU), C18H33N3O6 The thesis is divided into seven chapters. Chapter 1 gives a general introduction to the stereochemistry of polypeptide chains and the secondary structure classification: helices, β-sheets and β-turns followed by an overview of different types of weakly polar interactions involving the side chains of aromatic amino acid residues. This section also provides a brief overview of the conformational analysis of β-, γ- and higher ω-amino acid residues in oligomeric β-peptides and in α,ω-hybrid peptides. A brief discussion on X-ray diffraction and solution to the phase problem is also presented. Chapter 2 describes the crystal structures of the peptides, Boc-Leu-Trp-Val-OMe (LWV), the two polymorphs of Ac-Leu-Trp-Val-OMe (LWV1 and LWV2), Boc-Leu-Phe-Val-OMe (LFV), Ac-Leu-Phe-Val-OMe (LFV1) and Boc-Ala-Aib-Leu-Trp-Val-OMe (AULWV), in order to explore the nature of interactions between aromatic rings, specifically the indole side chain of Trp residues [1]. Peptide LWV adopts a type I β-turn conformation, stabilized by an intramolecular 4→1 hydrogen bond. Molecules of LWV pack into helical columns stabilized by two intermolecular hydrogen bonds, Leu(1)NH…O=CTrp(2) and Indole NH…O=CLeu(1). The superhelical columns further pack into the tetragonal space group P43 by means of a continuous network of indole - indole interactions. The peptide Ac-Leu-Trp-Val-OMe crystallized in two polymorphic forms: P21 (LWV1) and P212121 (LWV2). In both forms, the peptide backbone is extended and the crystal packing shows anti-parallel β-sheet arrangement. Similarly, extended strand conformation and anti-parallel β-sheet formation are also observed in the Phe containing analogs, LFV and LFV1. The pentapeptide AULWV adopts a short stretch of 310-helix. Analysis of aromatic - aromatic and aromatic - amide interactions in the structures of peptides LWV, LWV1 and LWV2 are reported along with the examples of 12 Trp containing peptides from the Cambridge Structural Database. The results suggest that there is no dramatic preference for the orientation of two proximal indole rings. In Trp containing peptides specific orientations of the indole ring, with respect to the preceding and succeeding peptide units, appear to be preferred in β-turns and extended structures. Crystal parameters LWV: C28H42N4O6; P43; a = 14.698(1) Å, b = 14.698(1) Å, c = 13.975(2) Å; Z = 4; R = 0.0737, wR2 = 0.1641. LWV1: C25H36N4O5; P21; a =10.966(3) Å, b = 9.509(2) Å; c = 14.130(3) Å, β = 104.94(1)°; Z = 2; R = 0.0650, wR2 = 0.1821. LWV2: C25H36N4O5; P212121; a = 9.533(6) Å, b = 14.148(9) Å, c = 19.53(1) Å, Z = 4; R = 0.0480, wR2 = 0.1365. LFV: C26H41N3O6; C2; a = 31.318(8) Å, b = 10.022(3) Å, c = 9.657(3) Å, β = 107.41(1)°; Z = 4; R = 0.0536, wR2 = 0.1328. LFV1: C23H35N3O5; P212121; a = 9.514(8) Å, b = 13.56(1) Å, c = 20.04(2) Å, Z = 4; R = 0.0897, wR2 = 0.1960. AULWV: C35H54N6O8.2H2O; P21; a = 9.743(3) Å, b = 22.807(7) Å, c = 10.106(3) Å, β = 105.73(2)°; Z = 2; R = 0.0850; wR2 = 0.2061. Chapter 3 describes the crystal structures of three peptides containing Trp residues at both N- and C-termini of the peptide backbone: Boc-Trp-Trp-OMe (WW), Boc-Trp-Aib-Gly-Trp-OMe (WUGW) and Boc-Leu-Trp-Val-Ala-Aib-Leu-Trp-Val-OMe (H8AU). Peptide WW adopts an extended conformation and the molecules pack into an arrangement of parallel β-sheet in crystals, stabilized by three intermolecular N-H…O hydrogen bonds. The potential hydrogen bonding group NE1H of Trp(1), which does not take part in hydrogen bonding interaction with an oxygen acceptor participate in an intermolecular N-H…π interaction. Peptide WUGW adopts a folded structure, stabilized by a consecutive type II-I’ β-turn conformation. The crystal of WUGW contains a stoichiometric amount of chloroform in two distinct sites each with an occupancy factor of 0.5 and the structure provides examples of N-H…π, C-H…π, π…π, N-H…Cl, C-H…Cl and C-H…O interactions [2]. The molecular conformation of H8AU reveals a 310-helix. The crystal structure of H8AU reveals an interesting packing motif in which helical columns are stabilized by side chain - backbone hydrogen bond involving the indole NH of Trp(2) as donor and C=O group of Leu(6) as acceptor of a neighboring molecule, which closely resembles the hydrogen bonding pattern obtained in the tripeptide LWV [1]. Helical columns also associate laterally and strong interactions are observed between the Trp(2) and Trp(7) residues on neighboring molecules [3]. The edge-to-face aromatic interactions between the indoles suggest a potential C-H…π interaction involving the CE3H of Trp (2) Crystal parameters WW: C28H32N4O5; P212121; a = 5.146(1) Å, b = 14.039(2) Å, c = 35.960(5) Å; Z = 4; R = 0.0503, wR2 = 0.1243. WUGW: C34H42N6O7.CHCl3; P21; a = 12.951(5) Å, b = 11.368(4) Å, c = 14.800(5) Å, β = 101.41(2)°; Z = 2; R = 0.1095, wR2 = 0.2706. H8AU: C57H84N10O11; P1; a = 10.494(7) Å, b = 11.989(7) Å, c = 13.834(9) Å, α = 70.10(1)°, β = 82.74(1)°, γ = 78.96(1)°; Z = 1; R = 0.0855, wR2 = 0.1965. Chapter 4 describes the crystal structures of four protected β-amino acid residues, Boc-(S)-β3-HAla-NHMe (BANH); Boc-(R)-β3-HVal-NHMe (BVNH); Boc-(S)-β3-HPhe-NHMe (BFNH); Boc-(S)-β3-HPro-OH (BPOH) and two β-dipeptides, Boc-(R)-β3-HVal-(R)-β3-HVal-OMe (BVBV); Boc-(R)-β3-HVal-(S)-β3-HVal-OMe (LVDV). Gauche conformations about the Cβ-Cα bonds (θ ~ ± 60°) are observed for the β3-HPhe residue in BFNH and all four β3-HVal residues in the dipeptides BVBV and LVDV. Trans conformations (θ ~ 180°) are observed for β3-HAla residues in both independent molecules in BANH and for the β3-HVal and β3-HPro residues in BVNH and BPOH, respectively. In all these cases except for BPOH, molecules associate in the crystals via intermolecular backbone hydrogen bonds leading to the formation of sheets. The polar strands formed by β3-residues aggregate in both parallel (BANH, BFNH, LVDV) and anti-parallel (BVNH, BVBV) fashion. Sheet formation accommodates both the trans and gauche conformations about the Cβ - Cα bonds [4]. Crystal parameters BANH: C10H20N2O3; P1; a = 5.104(2) Å, b = 9.469(3) Å, c = 13.780(4) Å, α = 80.14(1)°, β = 86.04(1)°, γ = 89.93(1)°; Z =2; R = 0.0489, wR2 = 0.1347. BVNH: C12H24N2O3; P212121; a = 8.730(2) Å, b = 9.741(3) Å, c = 17.509(5) Å; Z = 4; R = 0.0479, wR2 = 0.1301. BFNH: C16H24N2O3; C2; a = 20.54(1) Å, b = 5.165(3) Å, c = 16.87(1) Å, β = 109.82(1)°; Z = 4; R = 0.0909, wR2 = 0.1912. BVBV: C18H34N2O5; P212121; a = 9.385(2) Å, b = 11.899(2) Å, c = 19.199(4) Å; Z = 4; R = 0.0583, wR2 = 0.1589. LVDV: C18H34N2O5; P212121; a = 5.170(4) Å, b = 10.860(8) Å, c = 37.30(3) Å; Z = 4; R = 0.0787, wR2 = 0.1588. BPOH: C11H19N1O4; P1; a = 5.989(2) Å, b = 6.651(2) Å, c = 8.661(3) Å, α = 70.75(1)°, β = 77.42(1)°, γ = 86.98(1)°; Z = 1; R = 0.0562, wR2 = 0.1605. Chapter 5 describes a new class of polypeptide helices in hybrid sequences containing α-, β- and γ-residues. The molecular conformation in crystals determined for the octapeptide Boc-Leu-Phe-Val-Aib-(S)-β3-HPhe-Leu-Phe-Val-OMe (UBF8) reveals an expanded helical turn in the hybrid sequence (ααβ)n. A repetitive helical structure composed of C14 hydrogen bonded units is observed. Using experimentally determined backbone torsion angles for the hydrogen bonded units formed by hybrid sequences, the energetically favorable hybrid helices have been generated. Conformational parameters are provided for C11, C12, C13, C14 and C15 helices in hybrid sequences [5]. Crystal parameters UBF8: C60H88N8O11; P212121; a = 12.365(1) Å, b = 18.940(2) Å, c = 27.123(3) Å; Z = 4; R = 0.0625, wR2 = 0.1274. Chapter 6 describes the crystal structures of five model peptides Piv-Pro-Gly-NHMe (PA1), Piv-Pro-βGly-NHMe (PB1), Piv-Pro-βGly-OMe (PBO), Piv-Pro-δAva-OMe (PDAVA) and Boc-Pro-γAbu-OH (BGABU). A comparison of the structures of peptides PA1 and PB1 illustrates the dramatic consequences upon backbone homologation in short sequences. The molecule PA1 adopts a type II β-turn conformation in the crystal state, while in PB1, the molecule adopts an open conformation with the β-residue being fully extended. The peptide PBO, which differs from PB1 by replacement of the C-terminal NH group by an O-atom, adopts an almost identical molecular conformation and packing arrangement in the crystal state. In peptide PDAVA, the observed conformation resembles that determined for PB1 and PBO, with the δAva residue being fully extended. In peptide BGABU, the molecule undergoes a chain reversal, revealing a β-turn mimetic structure stabilized by a C-H…O hydrogen bond [6]. Crystal parameters PA1: C13H23N3O3; P1; a = 5.843(1) Å, b = 7.966(2) Å, c = 9.173(2) Å, α = 114.83(1)°, β = 97.04(1)°, γ = 99.45(1)°; Z = 1; R = 0.0365, wR2 = 0.0979. PB1: C14H25N3O3.H2O; P212121; a = 6.297(3) Å, b = 11.589(5) Å, c = 22.503(9) Å; Z = 4; R = 0.0439, wR2 = 0.1211. PBO: C14H24N2O4.H2O; P212121; a = 6.157(2) Å, b = 11.547(4) Å, c = 23.408(8) Å; Z = 4; R = 0.050, wR2 = 0.1379. PDAVA: C16H28N2O4.H2O; P21212; a = 11.33(1) Å, b = 25.56(2) Å, c = 6.243(6) Å; Z = 4; R = 0.0919, wR2 = 0.2344. BGABU: C14H24N2O5; P61; a = 9.759(2) Å, b = 9.759(2) Å, c = 29.16(1) Å; Z = 6; R = 0.0773, wR2 = 0.1243. Chapter 7 describes the crystal structures of a dipeptide, Boc-Aib-γAbu-OH (UG) and a tripeptide, Boc-Aib-γAbu-Aib-OMe (UGU) containing a single γAbu residue in each sequence. The structure of UG forms a reverse turn stabilized by a 10-membered intramolecular C-H…O hydrogen bonded ring. The peptide UGU crystallized in the triclinic space group P⎯1 with two molecules in the asymmetric unit resulting in a parallel assembly of sheets in crystals. Notably, the insertion of a single Aib residue at the C-terminus drastically changes the overall conformation of the structures. Crystal parameters UG: C13H24N2O5; P21/c; a = 16.749(3) Å, b = 5.825(1) Å, c = 16.975(3) Å; β = 111.82(1); Z = 4; R = 0.0507; wR2 = 0.1294. UGU: C18H33N3O6; P⎯1; a = 9.576(6) Å, b = 13.98(1) Å, c = 17.83(1); α = 85.31 (1); β = 77.46 (1); γ = 71.39 (1); Z = 4; R = 0.0648; wR2 = 0.1837.

The main purpose of this study was to compare the effectiveness of instruction based on constructivist approach over traditionally designed chemistry instruction on ninth grade students&amp / #65533 / understanding of chemical bonding concepts. In addition, the effect of instruction on students&amp / #65533 / attitude toward chemistry as a school subject and the effect of gender difference on understanding of chemical bonding concepts were investigated. Forty-two ninth grade students from two classes of a chemistry course taught by the same teacher in METU Development Foundation Private School 2000-2001 spring semester were enrolled in the study. The classes were randomly assigned as control and experimental groups. Students in the control group were instructed by traditionally designed chemistry instruction whereas students in the experimental group were taught by the instruction based on constructivist approach. Chemical Bonding Concept Test was administered to both groups as a pre-test and post-test in order to assess their understanding of concepts related to chemical bonding. Students were also given Attitude Scale Toward Chemistry as a School Subject at the beginning and end of the study to determine their attitudes and Science Process Skill Test at the beginning of the study to measure their science process skills. The hypotheses were tested by using analysis of covariance (ANCOVA) and two-way analysis of variance (ANOVA). The results indicated that instruction based on constructivist approach caused a significantly better acquisition of scientific conceptions related to chemical bonding and produced significantly higher positive attitudes toward chemistry as a school subject than the traditionally designed chemistry instruction. In addition, science process skill was a strong predictor in understanding the concepts related to chemical bonding. On the other hand, no significant effect of gender difference on understanding the concepts about chemical bonding and students&amp / #65533 / attitudes toward chemistry as a school subject was found.

The main purpose of this study was to compare the effectiveness of conceptual change oriented instruction accompanied with cooperative group work and traditionally designed instruction for removing misconceptions related to acid-base concepts. In this study 33 tenth grade students from two classes from METU Development Foundation Private School in the spring semester of 2003-2004 participated. There were two groups in the study. Students in experimental group received conceptual change oriented instruction with cooperative group work, and students in control group received traditionally designed instruction over a period of six weeks. Acid-Base Concept Test was administered to both groups as pre- and post-test. Students were also received Science Process Skill Test to determine their science process skills as pre-test and Attitude Scale Toward Chemistry to measure their attitudes toward chemistry as pre- and post-test. The hypotheses were tested by t-test, ANCOVA, and ANOVA. The results showed that the students in experimental group had significantly higher scores with respect to achievement related to acid-base concepts than the students in control group. On the other hand, there was no significant difference between attitude mean scores of students in experimental and control groups. Also, science process skill was a strong predictor for the achievement related to acid-base concepts. Alternatively, there was no significant difference between girls and boys in terms of understanding of acid-base concepts and attitudes toward chemistry. Alternatively, there was no significant interaction between gender and treatment on understanding of acid-base concepts and attitudes toward chemistry.

The purpose of this study was to explore the effects of inquiry-based high school chemistry course and gender differences with respect to students&rsquo / understanding of atom concept, learning approaches, motivational goals, self-efficacy, and epistemological beliefs. In this study, 47 ninth grade students from classes of a chemistry course were taught by the same teacher in Private Y&uuml / ce Science High School in the 2003-2004-spring semester were enrolled. There were two groups in the study. Two instruction methods used in this study were randomly assigned to each group. The experimental group who received Inquiry-Oriented Instruction (IOI) consisted of 22 students while the control group who received Traditionally Designed Chemistry Instruction (TDCI) consisted of 25 students. To examine the effect of the treatment on dependent variables / students&rsquo / understanding of atom concepts measured by Chemistry Achievement Test (CAT), meaningful learning and rote learning measured by Learning Approach Questionnaire (LAQ), learning-goal orientation, performance-goal orientation and self-efficacy measured by Achievement Motivation Questionnaire (AMQ), and epistemological beliefs measured by Science Knowledge Questionnaire (SKQ). t-test and ANOVA were used to test hypotheses of the study. The results showed that the students who used the inquiry oriented instruction had significantly higher scores with respect to achievement related to atom concept than the students who taught with the traditionally designed chemistry instruction. On the other hand, inquiry oriented instruction did not effect students&rsquo / learning approaches, motivational goals, self-efficacy, and epistemological beliefs. And also, the present study failed to find neither difference between boys and girls nor interaction between treatment (IOI vs. TDCI) and gender with respect to students&rsquo / understanding of atom concept, learning approaches, motivational goals, self-efficacy, epistemological beliefs.

The main purpose of this study was to compare the effectiveness of instruction based on 5E learning cycle model over traditionally designed chemistry instruction on tenth grade students&rsquo / understanding of acid-base concepts. Fifty- six tenth grade students from two classes of a chemistry course taught by the same teacher in Atat&uuml / rk Anatolian High School 2003-2004 spring semester were enrolled in the study. The classes were randomly assigned as control and experimental groups. Students in the control group were instructed by traditionally designed chemistry instruction whereas students in the experimental group were taught by the instruction based on 5E learning cycle model. Acid-Base Concepts Achievement Test was administered to both groups as a pre-test and post-test in order to assess their understanding of concepts related to acid-base. Students were also given Attitude Scale Toward Chemistry as a School Subject at the beginning and end of the study to determine their attitudes and Science Process Skill Test at the beginning of the study to measure their science process skills. The hypotheses were tested by using analysis of covariance (ANCOVA) and t-test. The results indicated that instruction based on 5E learning cycle model caused a significantly better acquisition of scientific conceptions related to acid-base produced significantly higher positive attitudes toward chemistry as a school subject than the traditionally designed chemistry instruction. In addition, science process skill was a strong predictor in understanding the concepts related to acid-base.