My lab class today-
"If you titrate acetic acid with NaOH, and apply the Henderson Hasselbalch equation, you can find the dissociation constant of the acid."
Pointing at the board--" Looking at the HH equation, we see that when the conc of the salt equals that of the acid, the pH is equal to pK. Now when will the concentration of the acid equal that of the salt?"
............silence................
"Ok, since the acid reacts to give the salt, when will this salt equal the remaining acid?"
again silence................
With exasperation"If I eat a cake, when will what I have eaten equal what I still have left?"
again silence for a minute..... then one person with great hesitation... "is it half?"
With relief"Yes! So now tell me about the acid"
Silence.............
Almost tearing my hair "Imagine the NaOH is eating up the acid-- when will the eaten up acid equal the leftover acid?"
"Halfway"
"Thank God"
This is not 7th class ..it is BSc 3rd year.......20-21 year olds.
2 comments:
I had someone explain this to me recently, and it now makes sense. They had an orientation program for teachers and they'd ask a simple question. Yet, everyone would hesitate for the fear of getting wrong. Everybody feels that they *should* get this right... and the stigma of getting it wrong (in public!) would probably be the defining event of the week in your life! As a student, I can empathise with this perfectly.
The only way to encourage them to speak up is to reduce the pressure on them and try and make the class more informal, in the sense where they shouldn't be afraid of making a fool of themselves while answering.
I agree. I realise this because I remember my student days too.
That is the reason that in their very first year I tell them and repeat this often, that they must not be afraid of making a mistake or even making a fool of themselves- just answer questions with some thought. I mention that they should see that their classmates are in the same boat.
Usually by the time they are in the second year, they are comfortable with their classmates and are used to my style of talking and that fear is considerably reduced.
The problem is that they are not used to being asked to think even a little bit in a classroom/academic setting. That is the reason the cake example is easy to answer, but the same question with acetic acid is not. This is inculcated in the "corporate" schools where they have to learn question -answers only and not question anything.
They too realise it--
Some of them do change by the end of three years and I feel a sense of achievement when they do.
Post a Comment