bond polarity and molecular polarity grc mini grant prototype storyboard #2

Bond Polarity and Molecular Polarity

GRC Mini Grant Prototype Storyboard #2

Tracking Sheet 2.0_v1.ppt by rjh 7.1.082.0_v1.ppt by blg 7.12.08

Bond Polarity and Molecular Polarity Outline2.1 Understanding Electronegativity - place arrows, recording (slides 4-6)2.2 Electron Distribution - drag to draw cloud (slides 7-10)2.3 cand Polarity - decide if distribution is symmetrical, calculate sort bonds from lowest to highest electronegativity, determine polarity recording (slides 11 - 15)2.4 Examine Three Molecules - make polarity prediction, assign +/ -, watch vector resolution animations, recording (slides 16-25)

Learning Goals- Students will be able to predict if a bond is polar or non-polar.- Students will be able to predict if a molecule is polar or non-polar.- Students can account for polarity of individual bonds in a molecule and then determine whether that molecule is symmetric or asymmetric.

Barbara Gonzalez:Suggestions for learning goals expressed in terms that are amenable to assessable outcomes.After completing this module, the learner will be able to:-Predict if a covalent bond is polar or nonpolar.-From molecular geometry and polarity of individual bonds, determine if a molecule has a symmetric and asymmetric electron distribution.-Predict if a molecule is polar or nonpolar.

Indicate which atom in each bond is the more electronegative by dragging a black arrow to the pair and orienting it so that the arrow head points to the more electro-negative atom.

C-H O-H N-H

2.1.1

C-H C-H N-H

Looks like you’re having trouble, would you like information aboutthe periodic trend of electronegativity? yes no

Indicate which atom in each bond is the more electronegative by dragging a black arrow to the pair and orienting it so that the arrow head points to the more electro-negative atom.

2.1.2

C-H O-H N-H

Indicate which atom in each pair is the more electronegative by dragging a black arrow to the pair and orienting it so that the arrow head points to the more electro-negative atom.

2.1.3

Is this your final answer? yes no

next

Please record your answer to the following

question: What is meant by electronegativity? Explain how you knew which way to point your arrows.



Barbara Gonzalez:The arrows are pointing to the electropositive atom in each bond. I copied this slide to create 2.1.3A with the arrows oriented correctly.

C-H O-H N-H

Indicate which atom in each pair is the more electronegative by dragging a black arrow to the pair and orienting it so that the arrow head points to the more electro-negative atom.

2.1.3A

Is this your final answer? yes no

next





Barbara Gonzalez:What do we do if the student responds incorrectly? Should we consider a tutorial here for the future?

Referring to the directional arrows you drew previously, use your mouse to dragthe gray cloud and create an electron distribution for each molecule. Click next when you’re ready to summon the next molecule.

2.2.1

next

1 of 4

C-H

C -H

Barbara Gonzalez:Referring to the directional arrows that you drew previously, use your mouse to drag the gray cloud to represent the electron distribution for each chemical bond. The cloud should be more larger(?) where the probability of finding electrons more often is greatest. Click NEXT when you are ready to summon the next chemical bond.

Referring to the directional arrows you drew previously, use your mouse tocreate an electron distribution for each molecule. Click next when you’re readyto summon the next molecule.

2.2.2

1 of 4

C-H

C -H

next

2 of 4

O-H

H - O


Referring to the directional arrows you drew previously, use your mouse tocreate an electron distribution for each molecule. Click next when you’re readyfor the next molecule.

2.2.3

1 of 4

C-H

C -H

next

2 of 4

O-H

H - O

3 of 4

H - N

N-H


Referring to the directional arrows you drew previously, use your mouse tocreate an electron distribution for each molecule. Click next when you’re readyto proceed.

2.2.4

1 of 4

C-H

C -H

2 of 4

O-H

H - O

3 of 4

H - N

N-H

next

3 of 4

H -H

H-H


2.3.1

C - H O - H

Identify the symmetry of the electron distributions in the four examples by clicking on either symmetric or asymmetric fin the green boxes below each one.

symmetric asymmetric




Placeholder for a research question dealing with symmetry (student open response).

N - H H - H

next

Barbara Gonzalez:

Please record your answer to the following questions: What do you think is meant by the term symmetric?Explain why the O-H bond is considered to be asymmetric?

Barbara Gonzalez:

Please record your answer to the following questions: What do you think is meant by the term symmetric?Explain why the O-H bond is considered to be asymmetric?

2.3.2

C - H O - H

Calculate the difference in electronegativity () for each example using the values in the table.





N - H H - H

next

= ____________

H C N O Atom

2.1 2.5 3.0 3.5

= ____________ = ____________ = ____________

Barbara Gonzalez:Include label/heading in the table. See added column below.

Barbara Gonzalez:Calculate the difference in electronegativity () for each bond using the values in the table.

2.3.3

C - H O - H

Sort the bonds in increasing order of the difference in electronegativity ( ) by dragging each block into the empty boxes below, from lowest to highest.





N - H H - H

next

= 0.4 = 1.4 = 0.9 = 0

lowest highest

2.3.4

H - H

You can determine whether a bond is polar or non-polar if you know the difference in electronegativity () between the two bonded atoms. If the difference value is less than 0.5, the bond is non-polar. If it’s greater, the bond is polar. Identify the polarity of each bond below by clicking either polar or non-polar in the purple boxes.





N - H O - H

polar non-polar

polar non-polar

polar non-polar

polar non-polar

C - H

= 0 = 0.4 = 0.9 = 1.4

2.3.5

H - H





N - H O - H

next

polar non-polar

polar non-polar

polar non-polar

polar non-polar

C - H

= 0 = 0.4 = 0.9 = 1.4

Please record your answer to the following: Explain how

the difference in electronegativity and the electron distribution relate to the polarity of the bond.

You can determine whether a bond is polar or non-polar if you know the difference in electronegativity () between the two bonded atoms. If the difference value is less than 0.5, the bond is non-polar. If it’s greater, the bond is polar. Identify the polarity of each bond below by clicking either polar or non-polar in the purple boxes.

2.4.1 Now you will examine the geometry of three different molecules: carbon tetrachloride, chloroform, and water. You will begin with carbon tetrachloride (CCl4), which has an electron pair and molecular geometry that is tetrahedral. A ball and stick representation of the molecule appears below. Drag the arrows to each bond, using the electronegativity values to indicate the direction of the arrow (the arrow head should point to the more electronegative atom).

H C N Cl O

2.1 2.5 3.0 3.0 3.5

Carbon tet diagram here

Is the electron distribution in all of the bonds symmetric or asymmetric? yes no

next

CCl4 CHCl3 H2O

2.4.2 Answer the questions in the orange box by typing your answers. Once you’ve made your predictions, assign a + and a - to each atom in all four bonds on the diagram below by dragging the symbols onto the molecule.

Based on the asymmetry of the bonds, would you predict that the four bonds are polar or non-polar? ____________

Is it possible for all four bonds in the molecule to be polar and the entire molecule to be non-polar? ____________

Based on that, do you predict the molecule is polar is non-polar? ___________________

Carbon tet diagram here

next

- +

CHCl3 H2O

H C N Cl O

2.1 2.5 3.0 3.0 3.5

CCl4

2.4.3 Now you will examine chloroform (CHCl3) which is a tetrahedral molecule. The ball and stick figure appears below. Using the electronegativity values in the table, drag the arrow to point to the more electronegative atom in each bond.

Chloroform diagram here

next

CHCl3 H2O

H C N Cl O

2.1 2.5 3.0 3.0 3.5

CCl4


2.4.4 Answer the questions in the orange box and then assign a + and a - to each atom in all four bonds on the diagram below.

Chloroform diagram here

next

- +

CHCl3 H2O




H C N Cl O

2.1 2.5 3.0 3.0 3.5

CCl4

2.4.5 Now you will examine water (H2O) which as an electron pair and molecular geometry that is tetrahedral. A ball and stick representation of the molecule appears below. Drag the arrows to each bond, using the electronegativity values to indicate the direction of the arrow (the arrow head should point to the more electronegative atom).

water diagram here

CCl4 CHCl3

H C N Cl O

2.1 2.5 3.0 3.0 3.5

H2O


Barbara Gonzalez:Now you will examine water, (H2O), which has an electron pair geometry that is tetrahedral and a molecular geometry that is bent.

2.4.6 Answer the questions in the orange box and then assign a + and a - to each atom in all four bonds on the diagram below.

Water diagram here

next

- +

CCl4 CHCl3 H2O




H C N Cl O

2.1 2.5 3.0 3.0 3.5

2.4.7 Click start on the movie below to determine the polarity of CCl4 and the accuracy of your prediction. When you’re ready, select CHCl3 and then H2O to see their movies.

Vector resolution animation

CCl4 CHCl3 H2O

Based on the asymmetry of the bonds, would you predict that the four bonds are polar or non-polar? ______YES______

Is it possible for all four bonds in the molecule to be polar and the entire molecule to be non-polar? _______NO_____

Based on that, do you predict the molecule is polar is non-polar? ______YES______

start >

2.4.8 Click start on the movie below to determine the polarity of the molecule and the accuracy of your prediction.


next

CCl4 CHCl3 H2O

CCl4




2.4.9 Click start on the movie below to determine the polarity of the molecule and the accuracy of your prediction.


next

CCl4 CHCl3 H2O

CCl4




CHCl3

2.4.10 Click on any of the movie icons to review. Answer the final question below.

stage

CCl4 CHCl3 H2O

Were your predictions correct? Why or why not?

bond polarity and molecular polarity grc mini grant prototype storyboard #2

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