ASSIGMNET 1| Research on student difficulties in Understanding Chemical reactions| Misconceptions on Strength of Acids and Bases| | Mariyam Zaina, 015482| | | TITLE & INTRODUCTION Title: Misconceptions on Strength of Acids and Bases Researches shows that students often develops new theories about how the natural world works, prior to formal science education and frequently those theories are different to those of scientists(Demircioglu et al. , 2005).
Students develop those scientific conceptions from many sources such as personal experiences (eg: observations), gender, peer interaction, media, language, symbolic representations, textbooks etc… In addition, sometimes teachers also serve as major sources for alternative conceptions (Chiu, 2005) and such self-constructed conceptions are referred as misconceptions. Misconceptions are ideas which are not in agreement with accepted scientific ideas (Demircioglu et al. 2005). If students have misconceptions they are then likely to reject the scientist’s viewpoints, thus it would be very important for teachers to find about the misconceptions about the concepts to be taught (Khurshid & Iqbal, 2009) It is known that secondary schools students found chemistry as one of the most difficult subjects and thus many students have difficulty in understanding the most basic concepts in the subject.
Researches shows that students have lot of topic in chemistry with misconceptions and one such examined topic includes acids and bases (Demircioglu et al. , 2005). Many studies show that students have a lot of complexity in understanding the right concepts in acids and bases. Some of them include that students often fail to give examples of weak acids and bases and also claims that pH is the tool more measuring acidity. And students often refer acids as chemicals hat are corrosive or chemicals that eat away everything. Furthermore students think that the more hydrogen ions present in a chemical the strength of its acidity increase. And such misconceptions make the topic acids and bases more abstract, boring and difficult to understand (Halim et al. , 2010). This research is conducted to clarify students such misconceptions or alternative theories on the concept “Strength of acids and Bases” under the topic Acids and Bases.
The misconceptions taken into consideration are: * Substances containing H are acidic and substances containing OH are basic * A strong acid doesn’t dissociate in water solution, because its intra-molecular bonds are very strong * Concentrated acids are dangerous but concentrated bases are not * As the value of pH increases, acidity increases * As the number of hydrogen atoms increases in the formula of an acid, its acidity becomes stronger * All acids burn and melt everything * All acids and bases are harmful and poisonous * Alkalis are strong bases * Strength and concentration mean the same thing The strongest acid is the most concentrated acid (Demircioglu et al. , 2005). Some important key term used in this research include misconceptions (defined in the first paragraph), Strong acid, weak acid, dilute acid, concentrated acid, This is a topic usually confused by students and most of the time they accidently confuse the specific terms such as “strong acid” with contracted acid or corrosive acid. In fact it means neither of those things. A strong acid is an acid which is fully ionized in solution and a weak acid is an acid which partially dissociates in solution.
Similarly a strong base is base which ionizes fully in solution and weak bases get partially ionized in solution (Strong and Weak Acids and Bases, n. d). Concentrated acid has a relatively large amount of solute dissolved in the solvent. A dilute acid has a relatively smaller amount of solute dissolved in the solvent (Acid Strength, n. d) In this research it is assumed that all the students who participated in the survey are students who studied chemistry and thus would be thorough with the topic acids and bases. And also the students have answered all the uestions individually without any help or guidance and have given honest answers according to their levels of understanding. Furthermore it is assumed that students would be able to draw the molecular representation of the dissociations of ions in water by showing the molecules or ions present. The Rationale From various researchers done on student’s understanding of the topic acids and bases it is found that lot of secondary schools students have very different ideas or misconceptions on the concept strong and weak acids and bases.
In a lot of situations students often describe ‘strong’ and ‘weak’ as being synonymous with ‘concentrated’ and ‘dilute’. And most of the time these misconceptions arise because teachers are not aware of students prior or existing knowledge about a concept or do not address to such alternative theories they have about the concept. Which lead to students into more confusion and let them go ahead with their wrong concept. So the purpose of this investigation was to find students misconceptions on the concept of strong and weak acids and bases via a questionnaire.
Furthermore the purpose of the research is to find the students misconceptions on the concept acids and bases in Maldivian schools and thus find ways to implement lesson which could address their misconceptions as future teachers. Procedure Research was conducted using a probing tool to find students misconceptions. And the tool used was a questionnaire with multiple choices, fill in the blanks using the best word from the words give and a question where students have to draw and show their ideas on the concept. The questionnaire was given to grade 25 students of grade 9 from Dharumavantha School.
Students were chosen randomly from five classes of 9. From each class 5 students were just chosen randomly and asked to fill the questionnaire (Refer appendix for all the questionnaire students have filled). After that the forms were collected and the data was analyzed and percentage of the students choices were found and presented in the result sections RESULT Question 1 – Misconception; Substances containing H are acidic and substances containing OH are basic Figure 1: Percentage of students’ choices for the question number one. According to 62. 5% students A is the best choice.
And no students have chosen D as the answer Question 2 – Misconception; Concentrated acids are dangerous but concentrated bases are not Figure 2: Percentage of students’ choices for the Question number 2. 52% students have chosen A as the answer while the rest of the students think the correct answer is D Questions 3- Misconception; as the number of hydrogen atoms increases in the formula of an acid, its acidity becomes stronger Figure 2: Percentage of students’ choices for the Question number 3 according to highest percentage of students’ choice B which is phosphoric acid is the strongest acid
Question 4 – Misconception; Alkalis are strong Bases Figure 2: Percentage of students’ choices for the Question number 4 the highest percentages of students have chosen A as the answer. But there isn’t a huge difference between students choices Question 5 – all the acids and alkalis are harmful and poisonous Figure 2: Percentage of students’ choices for the Question number 5 it shows that for this question different student had different views. And most of the students with 36% chosed A as the answer Question 6 – Misconception; All the acids will eat and burn everything away
Figure 2: Percentage of students’ choices for the Question number 6 According to 84% students not all acids will burn and eat everything away. Only some acids will burn and eat everything away. Question 7 – Misconception; Strength and Concentration means the same thing Figure 2: Percentage of students’ choices for the Question number 7 Result shows that most of the students do not have this misconception; only about 24% students have the misconception while 76% are well aware of the concept strength and concentrated Question 8- Misconception; as pH increases acidity also increases.
Figure 2: Percentage of students’ choices for the Question number 8 Almost all the students were clear about this concept that as pH increases acidity decreases Questions 9 – Misconception; A strong acid doesn’t dissociate in water solution, because its intra-molecular bonds are very strong. Figure 2: Percentage of students’ choices for the Question number 9 – 44% students were able to draw and show the microscopic dissociation of ions in strong and weak acids with all criterions present. And 8% students drew with some criteria missing.
And the rest of the 48% students had misconceptions about the dissociation of strong and weak acids in water Question 10 –Misconception; the strongest acid is the most concentrated acid Figure 2: Percentage of students’ choices for the Question number 9 – it shows that most of the students is quite clear with this misconception. Yet 36% students still have the misconception that the strongest acid is the most concentrated acid DISCUSSION The first misconception dealt in the research was one of the very basic concepts under acids and bases.
That is the definition for an acid and a base. A common misconception is that acids are chemicals with hydrogen (H) in the chemical formula and bases are chemicals with OH in the formula. 62. 5% students think that C2H5OH is basic as it has OH in its formula. 4. 2% students think C6H12O6 is both acidic and basic as it has both H and OH in its formula. While the rest of the 33. 3% gave the correct answer which is C6H12O6 and C2H5OH is neither acidic nor basic even though they have H and OH in the formula.
But the result also shows that all the students are aware that ammonia is not an acid even if it has H in its formula. Acid is a substance that gives H+ ions when dissolved in water. Acids are compounds that contain hydrogen, however there are compounds that contains hydrogen in their formulas but does not act as acids; for an example water, H2O, ammonia NH3. A base in definition is that substance which gives OH- ions when dissolved in water. Thus they are not substance with OH present.
There are many substances that contain OH and H, yet does not act as acids or bases (Acids, Bases and Salts, 2005). For an example Sucrose, C6H12O6, contains H and OH, however, when dissolved in water it dissolves as intact molecules and does not ionize to produce any H+ or OH- ions, as shown by the equation: C6H12O6(s) + H2O(l) C6H12O6(aq). Since sugar molecules do not lose any H+ or OH- ions, sugar is not considered an acid. Alcohols (C2H5OH) have a characteristic hydroxyl group, OH, covalently bonded to the rest of the molecule.
When alcohols dissolve in water they also dissolve molecularly and do not ionize. Since no OH- ions are released, alcohols are not bases (Concept or Skills Development, n. d). However from the research it shows that students are not very clear about this idea and because of that most of the students have chosen A as the answer. A student’s misconception is that only concentrated acids are dangerous while concentrated bases are not. This misconception also was proven from question 2, as 52% students have chosen concentrated HCl only as most dangerous.
Yet, the result also talks to two sides because almost half of the students have chosen the correct choice (D) which says that both concentrated acid and base is dangerous. Choice A was a misconception. Weak acids and weak bases are not dangerous, but both strong acids and strong bases can both be harmful to human tissue. For an example lime is very strong base and that is the reason why a very small amount of lime is present in concrete and mortar. And construction workers have to be very careful not to get it on their skins (Strong and Weak Acids and Bases).
Another misconception was that as number of hydrogen in the chemical formula increases the strength of acid increases. According to 65% students this is true and thus they have chosen H3PO4 as the strongest acid and almost all the students have given the reason for their choice as having the most number of hydrogen in the formula. 31% students have chosen the correct answer which is sulfuric acid which is the strongest out of the three and have given the correct reason as, it could fully ionize in solution. Only 3% students have chosen nitric acid as the strongest acid.
According to students the more hydrogen present it can contribute to more H+ to the solution, thus it would become stronger. The strength of an acid is determined by its ionization power which determined by the pKa value. The lower the pKa value the stronger the acid. Thus H2SO4 is the strongest ith pKa = -3. 1 followed by nitric acid (pKa= -1. 3) and phosphoric acid (pKa = 2. 12) (William, n. d) The reason for this misconception might be because students have not learnt the pKa values and not gone into such details which would help to explain why an acid is becoming stronger.
To clarify the misconception could give the pKa values as an extra information for the students or could make the students clearer on the concept that the strength depends on the amount of dissociation. Fourth question is about the misconception that alkalis are strong bases. Some students have the misconception that as alkalis is basic substances that dissolves in water they are strong bases. And from the survey it shows that 24% students do have this misconception.
But it shows that apart from this misconception, most (36%) students have another wrong concept that alkalis and bases are same. 28% students do know the right answer from the choices given. Results of 5th question show that just 24% of students had the misconception that all the acids and alkalis were harmful and poisonous. Majority of students (36%) think that only concentrated HCl and concentrated NaOH will be harmful and poisonous, which was the correct choice out of the acids and bases is given.
Dilute ethanoic acid would not be harmful as it would be used in many of the foods items as well. Also would not be dilute ammonia. Thus the result coveys the message that majority of students are clear about the above misconception. Yet there are few students with different views so as teachers need to show students the differences by showing examples as such. Sometimes students are not aware of the idea that they eat and drink acids, so if they know better acids such as citric acids, acetic acids would e able to clear this misconception Sixth, seventh and eight questions it shows that majority students do not have the misconception identified. Sixth question 84% students know the correct answers for the blank which is “some” acids would burn and eat everything away. Seventh question was check whether students really knows the difference between concentrated and strong acids. It was an application question and 76% students have given the right answer which is “concentrated”. Only 24% students had the misconception that ‘concentrated’ and ‘strong’ means the same.
The students might have given the correct answer because two concentrations were given. For those who have given the correct answer whether they really know the difference, a different type of question with the same misconception was given (question 10). The correct answer for the 10th question was C which shows the full dissociated acid and thus it would be the strongest. 64% students have chosen this as the answer. Which shows some students knows that strong acids are those which dissociate fully.
However majority of students from that 64% has given the reason for their answers wrong. According to them C is correct because it contains the most number of molecules. So that means students do have the misconception about the strong and concentrated acids. Also 36% students chose D as the answer and most of their reason was that it has no water. This shows that their think strongest acid is the acid with least water present or otherwise the most concentrated acid. Eighth question none of the students had the misconception that as pH increases acidity increases.
Some students might think as pH is the measure concentration of H+ ions as the pH increases the number H+ ions might increase thus would increase the acidity. Yet, all the students gave the correct answer for this question. For the 9th question a variety of answers were given. The misconception check was “the stronger the acid the lower the dissociation because the inter-molecular bond would be stronger and weak acids would dissociate more”. For this question it was checked whether the students had the following criteria’s.
In weak acid shown the H-F not dissociated and very few H+ and F_ ions dissociated and in strong acid H-Cl fully dissociated into H+ and Cl- ions. And even if students have shown the water molecules or not shown it is correct. 44% students did draw the diagrams correctly with all the criteria given and have given the reasons as strong acid dissociate fully while weak acids would do partially. 8% students drew almost correct dissociations, but they most of them have not shown the ionic forms. (Refer appendix for students’ answers). And majority of students had misconceptions.
Most of these students have shown more number of molecules in the strong acid side while less molecules’ in the weak side. Students have the concept that strong acids have more molecules’ and weak acid would have less. Only one student has given the reason as the stronger acid would have stronger bonds so dissociation would be lesser. Thus it can be concluded that majority does not have that misconception but they do have another misconception which is mostly related to now knowing the actual meaning of strong and weak acids and also confusing it with concentrate and dilute.
Considering the misconceptions it is important as teachers to take actions to eliminate such misconceptions. Firstly the students should be given instructions which foster conceptual understanding rather than rote memorization. Students are just given definitions of acids bases and they have memorized it, does not get any understanding as to how an acid becomes stronger weaker, concentrated or diluted (Yezdan, 2009). For an example students show the difference in this four by comparing the pH of the four types of acids; concentrated, dilute, weak and strong.
In the class the students could be given discussion with teacher or peers to reflect on what they learnt and thus come up with the conceptions they have and thus the teacher can help in correcting them (Yezdan, 2009) Students misunderstanding arises generally from their experience s in everyday life and such experiences could be used to even eliminate the misconceptions. For an examples from early child hood onwards by watching cartoons and all students think that an acid is something which will make a hole where ever put and it is always dangerous.
But could brainstorm students’ understanding about the weak acids present in the materials that are used in day today lives and relate it to weak acids being harmless. Also demonstrating student the difference between a strong acid and concentrated acid rather than just giving definitions ((Demircioglu et al. , 2005). Also could establish analogical thinking between real life examples and the unknown while learning new information could discard misconceptions. For example, teacher asks to the students if there is a relationship between the number of hydrogen atoms that the acid contains and acidic strength.
After taking students responses and guiding the discussions till getting the true answer go one step further and asks “Is H3P04 stronger than HCl? “. Then allows students to discuss again and reach the answer. In order to establish an analogical thinking with real life situations can ask “how do we measure the strength of the bulbs that we use at our homes? ” and guide the discussions until students reach the fact that “If a bulb gives off a lot of light it is strong, a little Light it is weak” and then helps students to establish the analogy of if an acid ionizes a lot, it is strong; ionizes a little, it is weak like in the case of bulbs.
Similarly, provide students to realize that only one bulb sometimes may give more light/ may be more powerful than the two or more bulbs like in the case of the acidic strength and the number of hydrogen atoms that an acid contain i. e. HCl is stronger acid than the H3P04 because it gives more hydrogen ions than H3P04 when dissociates in water although it contains smaller number of hydrogen atom. Some limitations of this research include that the research is based only onto answer of 25 students which is a very small sample size to know the extent of overall students understanding.
Also the sample is from one school, even the students understanding may differ in schools because of the differences in methodologies used in teaching same concept. Also even though it was assumed that students have given honest answers without help from anyone some students answers were very similar which should be because of copying or discussion so the authenticity is not very effective, need to make sure students do it individually. Conclusions
The purpose of the research was to find whether the misconceptions stated in the introductions were there in the students and to check the extent of students’ understanding on the concept ‘strength of acids and bases’. According to the results majority of students have a deeper understanding of the topic and does not have the most of the misconceptions stated. However some concepts such as “concentration is same as strength”, “as number of Hydrogen increases the acidity increase” and “substances with H in the formula is acidic and OH is basic”.
These three misconceptions were found in majority of students and thus need to be dealt as they are one of the very basic and important concepts. And since chemistry as the topics are very much interrelated if the misconception persists it can lead into further misconceptions. So during teaching need to give more attention of those areas and try to use methods such as analogical thinking, demonstrations, applications questions which would help to clarify their misconceptions. Furthermore need to check students’ prior knowledge before going into the new concepts as it would be the foundation for the new knowledge.
REFERENCES Acids, Bases and Salts. (2005). Retrieved on August 17, 2011 from http://www. krysstal. com/acidbase. html Acid Strength. (n. d). Retrieved on August 17, 2011 from http://media. rsc. org/Misconceptions/Miscon%20acid%20strength. pdf Chiu. ,M. H. (2005). National Survey of Students’ Conceptions in chemistry in Taiwan. Retrieved on August 17, 2011 from http://old. iupac. org/publications/cei/vol6/07_Chiu. pdf Concept or Skills Development. (n. d). Retrieved on August 17, 2011 from http://www. okstate. edu/jgelder/acidPage25. html
Demircioglu. G. , Ayas. A and Demircioglu. H. (2005). Conceptual change achieved through a new teaching program on acids and bases. Retrieved on August 17, 2011 from http://www. rsc. org/images/p3_Demircioglu_tcm18-31135. pdf Khurshid. , M and Iqbal. , M. Z. (2009). Children’s Misconceptions about Units on Changes, Acids and Laboratory Preparation of CO2. Retrieved on August 17, 2011 from http://pu. edu. pk/images/journal/ier/PDF-FILES/4-Childrens%20Misconceptions. pdf Halim. , N. D. A. , Ali. , M. B. , Yahaya. , N and Junaidi. , J. (2010).
Learning acids and Bases through Inquiry Bases Website. Retrieved on August 17, 2011 from http://teknologimalaysia. academia. edu/noordayana/Papers/393231/Learning_Acids_and_Bases_Through_Inquiry_Based_Website Strong and Weak Acids and Bases. (n. d). Retrieved on August 17, 2011 from http://www. sky-web. pwp. blueyonder. co. uk/Science/strongacids. htm William. , R. (n. d). pKa Data. Retrieved on August 17, 2011 from http://research. chem. psu. edu/brpgroup/pKa_compilation. pdf APPENDIX Raw data of the survey conducted | QUESTION 1| | QUESTION 6|
Choice | No. of students| %| | Choice | No. of students| %| A| 15| 62. 5| | Some| 21| 84. 0| B| 1| 4. 2| | All| 4| 16. 0| C| 8| 33. 3| | | 25| | D| 0| 0| | | | | | 24| | | | | | | | | | | | | QUESTION 2| | QUESTION 7| Choice | No. of students| %| | Choice | No. of students| %| A| 13| 52. 0| | Concentrated| 19| 76. 0| B| 0| 0. 0| | stronger| 6| 24. 0| C| 0| 0. 0| | TOTAL| 25| 100. 0| D| 12| 48| | | | | TOTAL| 25| 100. 0| | | | | | | | | | | | QUESTION 3| | QUESTION 8| Choice | No. of students| %| | Choice | No. of students| %| A| 7| 30. | | Increase| 25| 100. 0| B| 15| 65. 2| | Decrease| 0| 0. 0| C| 1| 4. 3| | TOTAL| 25| 100. 0| TOTAL| 23| 100. 0| | | | | | | | | | | | QUESTION 4| | QUESTION 9| Choice | No. of students| %| | Choice | No. of students| %| A| 2| 8. 0| | shown all the criteas | 11| 44. 0| B| 19| 76. 0| | Some criteria missing| 2| 8. 0| C| 2| 8. 0| | misinterpretation of the concept| 12| 48. 0| D| 2| 8| | TOTAL| 25| 100. 0| TOTAL| 25| 100. 0| | | | | | | | | | | | QUESTION 5| | QUESTION 10| Choice | No. of students| %| | Choice | No. of students| %| A| 9| 36. 0| | A| 0| 0. 0|