Chemical drawing: Mechanism answer type

• Pre-Text: Pre-Text can be used to write out a reaction that the student answer completes. For example, the pre-text can show the reactants in a reaction with an arrow pointing to the student response section where the students will enter the product of that reaction to complete it.
• Post-Text: Post-text can complete a reaction, following the reagents drawn by the students on the canvas.

Add pre-text or post-text

1. Select add pre-text or add post-text in the Answer box.
2. Enter the pre- or post-text using your keyboard and options from the editing toolbar and menus. These fields can include an image, link, or media, as well as text formatting options like bullets or TeX.

Remove pre-text or post-text

1. Select remove pre-text or remove post-text in the Answer box.
2. Enter the pre- or post-text using your keyboard and options from the editing toolbar and menus. These fields can include an image, link, or media, as well as text formatting options like bullets or TeX.

The starting molecules appear on the drawing canvas in student view. Provide reagents when you want students to add boxes, reaction arrows, and charges where needed, but don't want students to spend time drawing the molecules.

Draw molecules using Marvin JS (creates an MRV file)

1. Select Create in MarvinJS from the Answer box. The chemical editor opens for you to draw.
2. Draw the molecules, boxes, and reaction arrows you want students to see when they open the question.

   How students answer mechanism drawing questions (using the Marvin chemical editor)

   Quick steps: Draw a molecule

   1. Select a bond from the left toolbar. Single bond is the default.

      

   2. Point on the canvas to create the molecule. Carbon is active by default. Select Undo if you don’t initially get the results you want.

      H and C appearance —
      H is shown on the canvas only when hetero and terminal. C is shown only when the atom is terminal. (To change this default, adjust H and C visibility in the Properties area of the Answer box.)

      To change an atom on the canvas —
      Select an atom from the toolbar on the right. (If needed, open the  Periodic table first.) Point on the atom you want to replace on the canvas.

      To get out of atom mode —
      Select another tool, like a bond or charge.

   3. Select any other toolbar options to complete the molecule, like to add charges.
3. Select OK when you’re finished.

   The file is automatically named and appears below the Select MRV File button in the Answer box. The file also becomes available for selection from the Item Assets list.

Select an MRV file created using Marvin JS (Optional)

1. Choose Select MRV File to open the list of available MRV files for the item.
   

   To create an MRV file — Follow the above instructions to draw a molecule using Marvin JS.

2. Choose Select for the MRV file that you want. If you’re unsure which file to choose, look back in the item and check the filename.

   Unlike other image files, you cannot preview MRV files from the Item Assets list by selecting its file name. (Selecting an MRV file name from the Item Assets list shows the file's XML code.)

Edit the starting molecules MRV file

1. Select the filename link for the MRV file listed as the Starting Molecule.

   

2. Make your changes to the molecules using the Marvin JS chemical editor. Follow the above instructions to draw a molecule using Marvin JS.
3. Select OK when you finish.

Remove the starting molecules MRV file for this question

Select X after the MRV filename.

• Removing the molecule MRV from the Answer box does NOT remove the MRV file from the Item Assets list.
• To remove the MRV file from the Item Assets list, open the list and select Delete for the applicable MRV file. (You can open the list by choosing Select MRV file.)

Select the size of the Marvin JS workspace, which includes the drawing toolbars (along the periphery) and the canvas area (center).

• small (500 x 500 pixels) — Use for single step mechanisms with smaller molecules.
• medium (700 x 500 pixels) — Use when several molecules are required.
• large (1000 x 500 pixels) — The default. Use when questions require more drawing space than the medium setting. Don't use this size when the item layout is set for 2-columns.

Select or deselect properties to control how the Marvin JS chemical drawing tool appears and behaves for students working on chemical drawing - mechanism questions.

• For example, you might want to view R, S labels as you are creating correct and incorrect answers to create answers more quickly, or control whether hydrogen atoms are visible to students.
• See Properties for Marvin JS setup for details about the properties that apply to mechanism questions.

  H and C visibility
  Show R,S labels to authors

Enter a correct answer for students to see if they select Request Answer. The "Correct Answer" is for display purposes only and does not affect student grading.

1. Open the drawing tool from the Correct Answer Shown to Students area, select Correct Answer.

   To create a correct answer — Select Create in MarvinJS.

   To edit a correct answer — Select Correct Answer.

2. Draw the correct answer using the toolbar buttons, including the applicable boxes, reaction arrows, charges, or molecules.

   How students answer mechanism drawing questions (using the Marvin chemical editor)

   Quick steps: Draw a molecule

   1. Select a bond from the left toolbar. Single bond is the default.

      

   2. Point on the canvas to create the molecule. Carbon is active by default. Select Undo if you don’t initially get the results you want.
      
      H and C appearance — H is shown on the canvas only when hetero and terminal. C is shown only when the atom is terminal. (To change this default, adjust H and C visibility in the Properties area of the Answer box.)
      
      To change an atom on the canvas — Select an atom from the toolbar on the right. (If needed, open the  Periodic table first.) Point on the atom you want to replace on the canvas.
      
      To get out of atom mode — Select another tool, like a bond or charge.
   3. Select any other toolbar options to complete the molecule, like to add charges.
3. Select OK when you're finished.

Answer evaluators compare a student’s answer to a correct or incorrect answer for grading purposes. At a minimum, add at least one evaluator for a correct answer.

1. Add an answer evaluator by selecting it or by copying and pasting one.

   Add a new evaluator by selecting it Select Add Evaluator from the Answer Evaluators area of the Answer box, then choose an evaluator from the provided list of expressions. Descriptions of answer evaluators

   Copy and paste an evaluator already in the item For example, you can copy and paste the expressionOchemEvalMechCounter evaluator for different conditions, like the number of boxes, reaction arrows, or reaction and resonance arrows. Select Copy Evaluator for the evaluator you want. Select Paste Evaluator from the bottom of the Answer Evaluators area. The evaluator is pasted at the end. Expressions are evaluated in order starting at the top. To reorder the pasted evaluator, select the Move up Evaluator or  Move down Evaluator option.

2. Select either Grade as Correct or Grade as Incorrect.
3. Select or enter the conditions for the evaluator.

   For details about the conditions for an evaluator, select .

4. Wrong answer feedback: Add/delete (Optional)
   Wrong-answer feedback can help students learn from their mistakes or incorrect choices.

   Select Show this response and enter the wrong answer feedback for the applicable “Grade as Incorrect” answer for an evaluator, such as the Is evaluator (expressionOchemEvalIs).

   • Mastering provides the initial feedback "Incorrect; Try Again", followed by the wrong answer feedback text.
   • Mastering provides automatic wrong answer feedback for mechanisms with incorrect electron-flow arrows when you include the Mechanism Flows evaluator.

     For example, the automatic feedback provides a link to the products produced if a student answer doesn't contain both curved arrows for a deprotonation. Any feedback you add appears after this automatic feedback.

   • Wrong answer feedback you add can include an image, link, or media, as well as text formatting options like bullets or TeX. Enter the responses using your keyboard and options from the editing toolbar and menus.
   Delete wrong answer feedback

   Clear the feedback in the Show this response box for the applicable “Grade as incorrect” evaluator box, such as for expressionOchemEvalAtoms.

5. To add more evaluators, repeat steps 1-4.

Delete a wrong answer evaluator

Select   Delete evaluator (right) for the evaluator box in the Answer box.

For more about answer evaluators, see the following.

• How chemical grading evaluators work
• Add molecule/compound for comparison

  Applies to the Contains, Flows, Is, Starting Materials and Products, and Substructure evaluators for mechanism questions.

Follow-up text appears after a student completes a part question, whether the student answers correctly, exhausts all answer attempts, or requests the answer. Follow-up text can reinforce learning by providing more information or an interpretation of the answer the student just submitted.

1. Select the add follow-up text link from the Answer box.
2. Enter your answer feedback, using your keyboard and options from the editing toolbar and menus. Follow-up text can include an image, link, or media, as well as text formatting options like bullets or TeX.
3. To save your edits, select  Save (from the top toolbar) or the Save & Preview link (top right). Do NOT press Ctrl+S (Windows) or Command-S (Mac OS).

To delete follow-up text: Select the remove follow-up link.