Personal Tutor Checking Help

How the Personal Tutor checks and responds to each student's answer:

Imagine the student asking the Personal Tutor sitting next to him/her to check the calculated answer.

• The Personal Tutor checks for missing-, or incorrect units.

• The Personal Tutor checks for missing-, or incorrect non-unit labels.

• The Personal Tutor checks for the magnitude of an unanticipated incorrect answer. (Example: the answer is off by an order of magnitude.)

• The Personal Tutor checks, and provides a suggestion for an Anticipated Incorrect Answer. (Example: decimal point error, incorrect- or inverted conversion factor, etc.)

Let us look at the two problems we worked earlier with the chemical calculator.

A. Checking answers to a Density Calculation Problem (Qktour problem #2.3)

Here are a few examples to illustrate how the Personal Tutor would respond after checking several answers.

1. The Personal Tutor's response to a missing unit label: Let's suppose the student has calculated that the answer to be 1.08 grams, but enters the value, "108". (In response to this messsage, the student adds the missing unit.)

2. The Personal Tutor's response to an unanticipated "order of magnitude" answer. (The student now realizes that they have left out the decimal point.)

3. The Personal Tutor responds to an anticipated incorrect answer. (This is only one of several responses that the Personal Tutor might make to anticipated incorrect answers. This response suggests to the student to rethink how he should use the density formula to calculate the mass of the aluminum.

4. The Personal Tutor responds to a decimal point error. (This time the student's error is not quite as serious - requiring only a bit more care in the computations.)

5. The Personal Tutor responds to a correct answer.

(The student can now compare his setup to that provided by the Personal Tutor.) (This exapnded solution may be copied to the Clipboard for later review.)

B. Checking answers to a Mole Conversion problem (Qktour problem #3.31)

Solutions to this problem could include all of the unanticipated incorrect answer (missing labels, order of magnitude, etc.) and many of the anticipated incorrect answers (e.g. decimal point errors) that were made in the previous problem. Mole conversion problems, however, introduce additional conceptual errors related to the writing of chemical formulas and understanding how to calculate the molar mass from the formula.

Let us look at how the Personal Tutor would respond to two types of anticipated incorrect answers.

1. Response to a 1st-level Anticipated Incorrect Answer

The student asks Personal Tutor to check this answer, "2.85g". This message suggests that the student has used an incorrect chemical formula in the calculation of the molar mass used in the calculation. At this point, it is hoped that the student would go back an reexamine the problem setup and corrrect the mistake. If, however, the student does not see what is wrong with the chemical formula used to calculate the molar mass, he/she can take advantage of the second level of help offered by the Personal Tutor.

2. Response to a 2nd-level Anticipated Incorrect Answer

The student would enter the chemical formula, "CaOH", and have it checked. The Personal Tutor provides a second level of help, which may be enough of a hint for correcting the error.

3. Response to a missing non-unit label

Let us assume that the student corrects the error, and finds the correct answer, and has it checked. This answer is still not accepted for the problem as defined by the Personal Tutor since it is missing the non-unit label descriptor. Write the formula of calcium hydroxide in the right-hand box, or "drag and drop" the formula from Hints List box.)

This time the answer is accepted. (The student can compare his solution with that provided by the Personal Tutor.)

The Personal Tutor's solution, hjowever, does not include the non-unit labels.