WEEK FIVE

 

Liberato Cardellini

 

During the week I received 27 e-mails.  Three sent me the questionnaire, many asked info about the next written examination or what happen if one do a certain error, and few excused themselves for not coming for the written examination and one student of the previous year asked for an exam session.

Because the All Saints’ Day holyday, we have to reserve one big room for Saturday 8th.  It was a week of ordinary lessons, and I involved the students with many questions and with questions they have to discuss in the groups.  I gave also some advice about stoichiometric calculations, making them aware of possible errors during the solutions of certain problems.

 

Monday 3 (1.5 h)

I have collected 9 concept maps.  I have corrected 272 problems finding 12 wrong solutions and erroneous results. I found 4 original solutions to problem n. 5; I sent to my students a message entitled ‘Pure Genius’, because of the following solution:

 

 

end a logical procedure for solving problems on stoichiometric calculations.  During this week I prod my students to solve a problem with the density between the data.

 

Problem 6. 10.00 mL of a solution of H2SO4 that is 2.485% by weight (density 1.015 g/mL) are diluted to 100.0 mL.  How many milliliters of NaOH 1.000 x 102 M are necessary to neutralize 20.00 mL of the H2SO4 solution prepared before?

During week four the students solve this problem together in the groups.  The solutions’ result range from 2.56 x 104 mL to 9.66 L.  Because I know they have a huge difficulty with this type of problem, I asked them to solve the problem again, as homework, writing the reasoning or the explanations at every steps before doing calculations or apply formulas.

 

Thursday 6 (2 h)

I have collected 4 concept maps.  I have corrected 194 problems finding 16 wrong solutions and erroneous results.  The reason they made just few concept maps is because they have another written examination.  They have to segment they time between three different courses (an maybe the TV).  A lot of commitments !

 

Friday 7 (3 h)

I have collected 6 concept maps.  I have corrected 128 problems finding 23 wrong solutions and erroneous results.  I asked a student to come to the blackboard, asking him to think aloud, while we solved the problem with density.  In the meantime the other students do the same by themselves or with a neighbour, or negotiate with me about some step of the solution.

Of the 40 solutions of problem 6, only 5 was OK; some solutions were unfinished, and 20 wrong for several reasons as calculation errors, distraction, do not consider the coefficients of the chemical equation, and so on. Two students made this calculation: (10.00 mL) x (1.015 g/mL) = 10.15 g H2SO4.

 

Saturday 8 (2 h)

The students completed the GALT questionnaire and then solved the three problems as written examination.  I corrected 168 problems and the results where for me a bit disappointing because only four students got the maximum score.  Following an advice of a friend, on Sunday I sent to my student the same problem 6 whit a alteration of the text, as homework.

 

A window in my office.

Pile of solutions: 2,619 from the fourth week + 930 = 3,549.