Questions we ask and Misconceptions of Chemical Concepts in African Context. Sileshi Yitbarek Münster June 22, 2006

Transcription

1 Questions we ask and Misconceptions of Chemical Concepts in African Context Sileshi Yitbarek Münster June 22, 2006

2 QUESTIONS WE ASK

3 Goal (Zweck) Content (Text book ) Evaluation (bewerten) Instruction (Teaching-Learning)

4 Questions we ask: Traditional Versus Conceptual Questions in Chemistry Purpose: To compare achievement on the Traditional Vs Conceptual questions. Area of Study: Stoichiometry Gas Law Instruments: Two-tiered Questions (Traditional versus Conceptual Questions)

5 Methodology: Subjects: First year students of Natural Science Stream, KCTE. Addiss Ababa Ethiopia. Sample size: 38 out of 96 students Sampling: Simple Random Test: Two-tiered questionnaire Analysis: f, %, X2

6 Categories of Questions: I. Traditional: Lower-order questions a. Recall: facts, definitions or recall explanations. Example: 1. What is the symbol for Potasium? 2. Define ionization Energy. b. Algorithimic: use information or processes in a familiar way. Example: 1. A given mass of gas occupies 5L at pressure of 0.5atm and 50 K. Calculate the pressure of the gas if it is cooled to 10K at constant volume. 2. Determine the chloride ion concentration in a saturated solution of AgCl (Ksp = 1.8 x 10-10)

7 ..Categories of Questions: II. Conceptual: Higher-Order Questions Transfer of knowledge to a new situation Assess underlying ideas behind chemical phonemena Cause to visualize a system and reach a conclusion Example: Iron combines with oxygen and water from the air to form rust. If an iron nail were allowed to rust completely, one should find that the rust weighs: (a) less than the nail it came from. (b) the same as the nail it came from. (c) more than the nail it came from. (d) It is impossible to predict. What is the reason for your answer?

8 A. Stoichiometry (Lythcott, 1990; Nurrenbern & Pickering, 1987) Question 1: ( Traditional) Balance the following reaction: N 2 + H 2 NH 3 N 2 + 3H 2 2NH 3 Question 2: ( Conceptual) Which of the following pictorially represent the above balanced chemical equation? Let: =Nitrogen; and = Hydrogen (a) + (b) + (c) + (d) + (e) +

9 Stoichiometry Table: Frequency and Percent responses for traditional and conceptual Stoichiometry question Question 1: Traditional (N=38) f and % of students answers to traditional question Question 2:Conceptual (N=32) f and % of students correctly answered conceptual question out of those who answered the traditional question Correct Incorrect Correct Incorrect Stoichiometry c a (7) b (9) d(3) e(0) f(9) Frequency (f) Percent (%) 84% 16% 12.5% 87.5% Conclusion: Additive view rather than an Interactive one. Lack of understanding of the purpose of Coefficients and subscripts Students perceive the balancing of equations as a strictly algorithmic (plug- and-chug)

10 B. Gas Law (Mulford, 1996) Instruments: Question 1: (Traditional) A given mass of gas occupies 5L at pressure of 0.5atm and 50 K. Calculate the presure of the gas if it is cooled to 10K at constant volume. a. 2.5 atm b. 0.5 atm c.0.1 atm d. None Questions 2:(Conceptual) The following diagram represents a cross section area of a 5L steel tank filled with hydrogen (H2) gas at 50K and 0.5 atm pressure. ( The dots represent the distribution of H2 molecules) If the tanker is cooled to 10 K, which of the following diagrams illustrate (show) the distribution of Hydrogen (H2) molecules, assuming there is no change in state.

11 Gas law Table: Frequency and percent responses for Traditional and Conceptual gas question Question 1: Traditional (N=38) Question 2: Conceptual (N=33) f and % students answers f and % of students choosing particular to traditional questions answers to conceptual question out of those who correctly answered the traditional question Correct Incorrect Correct Incorrect Gas Law C (a,b,d) a b (3) c (15) d(3) Frequency (f) Percent (%) 87% 13% 36% 64% Conclusion: The above questions were framed to ask students to relate temperature and gas distribution in the absence of change of state and volume. Students miss the very important concept that relates: T = K.E= Speed Gases occupy the entire volume of the container

12 Summary: Finding and Analysis for Conceptual and Traditional Table: Frequency and Percent responses for traditional and conceptual questions Question 1: Traditional (N=38) f and % students answers to traditional questions Question 2; Conceptual (N=38) f and % students answered to conceptual questions out of those who correctly answered the traditional questions Correct Incorrect Correct Incorrect Gas Law C (a,b,d) a b (3) c (15) d(3) Frequency (f) Stoichiometry c a (7) b (9) d(3) e(0) f(9) Frequency (f) Average Percent 85% 15% 24% 76% Conclusion: Only about one-fourth correctly conceive the concepts of Gas law and stoichiometry Computed (X2 = 26.57)> Critical value (x2 = 6.64) at <0.01 and df=1 Success= Traditional >Conceptual ( In Both gas Law and Stoichiometry)

13 Recommendation: Teachers should include conceptual questions when they examine Pictorial representations of the Micro-level should be included in: Students textbooks, and Instruction

14 References: Fensham, P. et al.(ed).(1994). The Content of Science: A constructive approach to its learning and teaching. UK: The Falmer Press Gabel,D.L, Samuel, K.V. and Hunn, D.(1987). Understanding the Particulate Nature of Matter. Journal of chemical Education.Vol.64 No8pp Mulford, D. R. (1996). An Inventory for Measuring College Students Level of Misconceptions in First Semester Chemistry. A thesis submitted to Purdue University. Nakhleh, B.Mary. March (1992). Why Some Students Don t Learn Chemistry. Journal of Chemical Education. Vol 69, No3, pp Sawrey, B.A.(1990). Concept Learning versus Problem Solving: Revisited. Journal of Chemical Education. Vol.67, No.3 pp Yarroch, W.L.(1985). Student Understanding of Chemical Equation Balancing. Journal of Research in Science Teaching. Vol.22, No.5,Pp

15 Misconceptions of Chemical Concepts in African Context

16 Study Questions: What misconceptions do grade 10 and grade 12 students held? To what extents do the misconceptions differ within and between grade 10 and grade 12 students?

17 Areas of Study: Concept Studied Reference Litrature 1. Solutions Nekhleh (1992), Wandersee (1994), and Fensham, et al (1994). 2. Macro and micro-properties Temechegn, 2002; Mulford, 1996; BenZvi etal, Mole Cervellati et al, 1982; Novick, S. & Menis.J Particulate nature of matter Mulford, 1996;Grifiths and Preston,1992; Gabel et al, Conservation of mass Mulford 1996; Bodner, Equation and Stoichiometry Lythcott, 1990; Sawrey, 1990; Nurrenbern & Pickering, 1987; Yarroch, 1985; Kolb, Changes of state Mulford, 1996; Osborne & Cosgrove, Gas Mulford, 1996

18 Subjects: Sample Size: G students - 48 % F total of 329 G students - 35 % F The average age: G 10 = 16.6 years and G 12 = 17.6 years Background: Both groups took chemistry as a separate subject since grade 7

19 Schools data were collected: (Addis Ababa) Name of General Grade 10 (N=163) Name of Preparatory Grade 12 (N=166) Secondary Number of School, Number of School, G10 Participants G12 Participants 1 Kokebe Tsibah 35 1 Addiss Ketema 34 2 Lem 29 2 Keftegna Arat 31 3 Medhanialem 35 3 Medhanialem 35 4 Menelik II 33 4 Menelik II 33 5 Wondiyirad 32 5 Wondiyirad 33

20 Techniques of data analysis: SPSS/version-9 Descriptive statistics: Mean, Standard Deviations and Percent Test for significance: t- test

21 ANALYSIS AND INTERPRETATION OF FINDINGS A. Solutions 1. Figure 1 represents a 1.0-L of sugar solution. The dots in the magnification circle represent the sugar molecules at a very small portion. In order to simplify the diagram, the water molecules have not been shown. 12 molecules Figure 1 Figure 2 Which response represents the view of the same portion after 1.0 L of water were added Disappear 36 molecules 6 molecules 12 molecules 24 molecules (a) (b) (c) (d) (e)

22 Solutions Percentage distribution: (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Comparison t321 = , p < ;Not Statistically significant difference at.05 level. Response comparison with other study Alternative Conception (Responses)* Mulford's Study, 1996 (Australia) Present Study (12 th grade) 2003 (Ethiopia) 6 molecules-correct response 75% 32%

23 B. Macro versus Micro properties Q.1 A copper wire has the following properties: i: Conduct electricity ii: Reddish color iii: Combines with oxygen to form Cupric Oxide iv: All of the above properties v: None of the above properties Which of these properties would be the same for one single atom of copper obtained from the sample? (a) i (b) ii (c) iii (d) iv (e) v Percentage distribution: N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Comparison: t324 = , p < 0.094; Not Statistically significant difference at.05 level

24 C. Mole Q1. Which of these three sets contains equal mole of Tin (Sn), Magnesium (Mg), and Sulfur (S)? (a) (b) (c) 100 g of Sn 100 g of Mg 100 g of S 100 atoms of Sn 100 atoms of Mg 100 atoms of S 100 cm 3 of Sn 100 cm 3 of Mg 100 cm 3 of S (d) All of the above. (e) None of the above. Percentage distribution: (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Comparison: t319 = , p < 0.011; Statistically significant difference at.05 level.

25 .Mole Q2. Which of the following represent 1 mole of a substance, at STP (Standard Temperature and Pressure)? a dm3 (L) solid carbon dioxide. b L liquid carbon dioxide. c L gaseous carbon dioxide. d. All of the above. e. None of the above. Percentage distribution: N a (%) b(%) c(%) d(%) e(%) (Q#) Grade Grade Grade Grade Grade Grade Q# Comparison t322 = , p < ; Not Statistically significant difference at.05 level.

26 D. The Particulate Nature of matter Q1. What would ultimately be found if you divide and subdivide a drop of water into smaller and smaller parts, without destroying the water itself? a. it will disappear. b. it can be divided with out limit (indefinitely). c. can be reached at a point where division is impossible. d. a drop of water is so small that it can t be divided. Percentage distribution N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Comparison: t323 = , p < 0.053; No statistically significant difference at.05 level

27 .The Particulate Nature of Matter Q2. What is the approximate number of carbon atoms, assuming placed side by side, that can cover a length of 1cm, a. 10-1,000 carbon atoms b. 1,000 10,000 carbon atoms c. 10, ,000 carbon atoms d. 1,000,000-20,000,000 carbon atoms e. 40,000,000-50,000,000 carbon atoms Percentage distribution N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Comparison: t302 = , p < 0.04; Statistically significant difference at.05 level

28 .The Particulate Nature of Matter Q3. Draw a liquid after the solid melts and draw a gas after the liquid boils. Melts Boils Solid Liquid Gas Description: Summary of the responses [using Gabel, et. al. (1987) criteria] Criteria Grade 10 Grade 12 L G L G Conservation of particles Conserved 41.32% 31.71% 55.57% 53.47% Proximity of particles Far apart to one another relative to solids 99.10% % 79.26% % Far apart to one another relative to 73.64% 79.26% liquids Orderliness of Particle arrangement Disordered (relative) 41.07% 60.71% 66.67% 78.68% Location of particles in container Bottom of the container 58.92% 6.72% 59.70% 2.16% Evenly distributed through out 39.29% 93.28% 39.55% 94.24% Top of the container 1.79% 0.00% 0.75% 3.6% Constancy of particle size Constant (the same) 88.68% 82.73% 91.61% 89.29%

29 E. Conservation of mass Q1. What is the mass of the solution when 1 kilogram of salt is dissolved in 20 kilograms of water? a. 19 kilograms. b. 21 kilograms. c. 20 kilograms. d. Between 20 and 21 kilograms. e. More than 21 kilograms. Percentage distribution: (Q#) Grade Grade Grade Grade Grade Grade Q# N a (%) b(%) c(%) d(%) e(%) Comparison: t322 = , p < 0.003; Statistically significant difference at.05 level.

30 Conservation of mass Comparison with other studies Alternative Conceptions (Responses) Mulford's Study (1996) Present Study Grade Kilogram 1 % 4 % 21 Kilogram 72 % 58 % 20 Kilogram 11 % 14 % Between 20 and % 17% Kilogram More than 21 Kilogram 1% 6 % Comparison: Comparatively students in Mulford s study performed better than the present study.

31 Conservation of mass Q2. Iron combines with oxygen and water from the air to form rust. If an iron nail were allowed to rust completely, one should find that the rust weighs: (a) less than the nail it came from. (b) the same as the nail it came from. (c) more than the nail it came from. (d) it is impossible to predict. Q3. What is the reason for your answer in question 3? a. It decomposes to other materials. b. It forms an oxide but the weight remains constant. c. The weight of oxygen can vary from place to place. d. Rust contains iron and oxygen. Percentage distribution: (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Q# Comparison: Q2* t322 = 1.144, p < 0.253; Not Statistically significant difference at.05 level. Q3** t320 = , p < 0.101; Not Statistically significant difference at.05 level.

32 Conservation of mass Comparison with other studies: Response comparison with other similar study for question #2 and #3 Responses Percentage of students responded choice-c to question #2 Grade 12 of the present study Mulford s study (1996) Australia 30% 46% Percentage of students responded both #2(c) & #3(d) 26% 44% N.B In this study both responses and reasons which are in line with the conceptions held by the scientific community were found to be less compared with Mulford s study.

33 Q4. When a match burns in a closed container, some matter is destroyed. Is this statement true or false? a. True b. False Percentage distribution: Conservation of mass Q5. What is the reason for your answer in question 4? (a) Chemical reaction causes mass to disappear. (b) Matter is consumed by the flame. (c) The mass of ash is less than the match it came from. (d) The atoms are not destroyed, they are only rearranged. (e) The match weighs less after burning. (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Q# Comparison Q4* t322 = , p < 0.002; Statistically significant difference at.05 level. Q5** t319 = , p < 0.000; Statistically significant difference at.05 level.

34 F. Equations, and Stoichiometry Q 1. The diagram represents a mixture of H 2 and O 2 molecules in a closed container. Hydrogen gas Oxygen gas Which diagram shows the product (water molecules) after the mixture reacts according to the equation? 2H 2 + O 2 2H 2 O (a) (b) (c) (d) (e)

35 .. Equations, and Stoichiometry Percentage distribution: N a (%) b(%) c(%) d(%) e(%) (Q#) Grade Grade Grade Grade Grade Grade Q# Comparison t321 = , p < ; Statistically significant difference at.05 level.

36 .. Equations, and Stoichiometry Q2. The reaction between reactant X( ) and reactant Y ( )is shown in the following diagram. Based on the above diagrams, identify the equation that can best describe the reaction? (a) 3X +Y 6 X 3 Y 6 (b) X 3 +6Y 3X6Y (c) 3X + 3Y 2 3XY 2 (d) 3X +6Y 3XY 6 (e) 3X +6Y Percentage distribution: 3XY 2 (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Comparison t325 = , p < ; Statistically significant difference at.05 level.

37 G. Changes of States Q1. Assume a beaker of pure water has been evaporated completely in a closed container. What is the composition of the vapor? (a) Air. (b) Oxygen gas and hydrogen gas. (c) Water. (d) Water, hydrogen and oxygen. (e) Heat. Percentage distribution: (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Comparison t326 = , p < ;Not Statistically significant difference at.05 level.

38 Changes of States Response comparison for question #1 of the present study with other studies Alternative Conceptions (Responses) Comparison-1 Osborne and Cosgrove (1983) Late high school (Age16) Present Study 10 th grade (Age~16) Comparison-2 Mulford First year college(1996) (Age~17) Present Study 12 th grade (Age~17) Air ~27% 15.3% 5% 4.2% Oxygen gas and hydrogen gas Steam (Water or Water vapor) ~45% 66.9% ( ) 55% (43% + 12%) 74.0% ( ) ~27% 11.0% 38% 15.2% Heat ~1% 6.7% 2% 6.7% Shaded = Currently accepted by the scientific community

39 . Changes of States Q#2. The circle on the right of picture-1 shows a magnified view of a ver small portion of liquid water in a closed container. What would th magnified view on the right of picture-2 show after the wate evaporates? Picture-1 Picture-2 Which of the following diagrams represent the magnified view on the right of picture-2 show after the water evaporates? (a) (b) (c) (d) (e)

40 Changes of States Percentage distribution: (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Comparison t323 = , p < ;Not Statistically significant difference at.05 level.

41 Changes of States Response comparison of written question(q#1) versus pictorial (Q# 2) Alternative conception (Response)* Grade 10 Grade 12 Written (Q# 1) Pictorial (Q#2) Written (Q# 1) Pictorial (Q#2) Air 15.3% Not Asked 4.2% Not Asked Oxygen gas and Hydrogen 44.2% 10.0% 57.0% 9.1% gas Water 11.0% 13.1% 15.2% 21.2% Water, Oxygen and Hydrogen 22.7% 16.9% 17.0% 14.5% Oxygen and Hydrogen Not Asked 23.1% Not Asked 31.5% Heat 6.7% Not Asked 6.7% Not Asked Disappears Not Asked 36.9% Not Asked 23.6% Shaded = Currently accepted by the scientific community

42 .Changes of States Q3. A glass of cold Coca-Cola forms a coat of water on the outside of the glass (Often referred to as 'sweat'). How does the water get there? a. Water vapor condenses from the air. b. Water evaporates from the Coca-Cola and condenses on the outside of the glass. c. The glass acts like a semi-permeable membrane and allows the water to pass. d. The coldness causes oxygen and hydrogen from the air combine on the glass forming water. e. The carbon dioxide found on the coca cola mix with the air when we open the bottle and it forms water droplets. Percentage distribution: (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Comparison t320 = -.285, p < ;Not Statistically significant difference at.05 level.

43 H. GAS 1. A 1.0-gram sample of solid iodine is placed in a tube and the tube is closed after all of the air is removed. The total weight of the tube and the solid iodine is 27.0 grams. The tube is then heated until all of the iodine evaporates and the tube is filled with iodine gas. What will be the total weight after heating? a. less than 26.0 grams. b grams. c. 0.0 grams. d. more than 28.0 grams. e grams. Percentage distribution: 2. What is the reason for your answer in question #1? a. The only change is in the physical state of the substance. b. Weight of solids is greater than gases. c. Iodine after evaporation becomes weightless. d. Pressure increases and as a result the total weight increases. e. Only the mass of the tube remains. (Q#) N a (%) b(%) c(%) d(%) e(%) Grade Grade Grade Grade Grade Grade Q# Q# Q#1 t321 = , p < ;Statistically significant difference at.05 level. Q#2 t315 = , p < ;Statistically significant difference at.05 level. Percent response for both question #2(e) and 3 (a)* Grade 10 = 20% ; Grade 12= 45%

44 Summary Remark Grade Grade % 70 % Can t estimate correctly the size of the atom 66 % 56 % Believe matter is continuous 80 % 70 % Can t distinguish between the properties of a single atom of copper and a copper wire 73 % 75 % Wrongly conserve number of moles and number of molecules during chemical reaction 54 % 42 % Can t conserve mass during solution formation 65 % 70 % Students believe that the rust weighs less than the iron it came from 64 % 47 % Believes matter is destroyed when a match burns 73 % 59 % Students can t associate the mole exclusively with the number of particles 68 % 58 % Can t restrict the molar volume at STP to gases 79 % 58 % Can t differentiate subscripts and coefficients, and has an additive view of a chemical reaction 70 % 74 % Believe that water breaks into its component during evaporation 75 % 65 % Believe that gases contracted on cooling; 55% 36 % Believe that gases are weightless 28 % 19 % Students doubled concentration of a solution when it is diluted by a factor of two

45 Conclusions: 1. The study indicated that majority (>50%) of G10 and G12 do not master the chemical concepts studied. 2. Comparison: Comparative Correct response G12 students difference is not significant in majority of the concepts compared to G10 In Present study Correct Concepts are low compared to other studies

46 Recommendations: Based on the finding the following recommendations are made: 1. Research should focus to try to retrace the possible root causes to the misconceptions found in this study. The possible root causes can be found in: Student textbooks Chemistry curriculum Methodology Age The teachers Motivation Evaluation th d Background/Prio r knowledge Instructiona l materials Learning conditions

47 Recommendations 2. Next after identifying the root causes research should be done to bring about conceptual Growth: This opportunity must be taken in order to introduce changes in the contents, methods and assessment of chemistry teaching. 3. Teachers, Curriculum developers, Text book writers should: Be encouraged to actively search (Identify) for students' alternative conceptions attempt to design teaching/ learning, which builds on rather than ignores such conceptions.

48 Thank You Very Much Vielen Dank