## Friday, July 8, 2011

### Activity 8

Activity 8: Exploration of Chemistry

For activity 8, students have a choice to explore other topics of chemistry presented in the PhET simulations.

Physics Web Search: Electricity & Magnetism

Part I

1.       On the desktop, find the Physics Animations Folder

2.       Open  “Balloons”

3.       Check “Show all Charges.” Nothing else should be checked.

4.       Rub the balloon on the shirt

5.       What overall charge does the balloon now have? Negative charge

6.       What overall charge does the shirt now have? Positive charge

7.       What happens when you drag the balloon away from the shirt and let it go? It comes back towards the shirt.

8.       Why? The opposite charges are attracted to each other.

9.       Reset

10.   Check “Wall”

11.   Rub the balloon on the shirt again.

12.   What happens to the negative charges in the wall when you move the balloon near it? They move away.

13.   What happens to the positive charges in the wall when you move the balloon near it? Nothing, they stay the same.

14.   Why don’t all the positive charges move toward the balloon?  Because the balloon has more of a negative charge and so they don’t feel that they need to push away.

15.   Hold the balloon in between the wall and shirt and release it

16.   Why doesn’t the balloon just stay in the middle? Because there are two forces that are attracting it.

Part II

1.       Open “Travoltage”

2.       Experiment with rubbing Travolta’s foot against the carpet and touching his finger to the door handle.

3.       Now try building up charge while his finger is on the door.

4.       What happens? The charge goes right to the door and doesn’t spend much time in the body.

5.       Move his finger away again and build up another charge

6.       When Travolta’s finger is near the door knob, what happens to the electrons currently in the metal door knob? They attract the electrons in his body.

7.       This _________?_________ a local _______?________ charge in the door knob.

8.       Why are shocks worse when you touch conductors rather than insulators? Because you feel the shock.

9.       If you take your hat off on a dry winter day, sometimes your hair will stand up.  Explain this phenomenon. This is because your hair has been rubbing on the hat, like when the balloon rubs on the sweater, and the opposite charges attract each other.

Part III

1.       Open “Electric Hockey”

2.       The goal of this game is to get the black positive puck to go in the goal.

3.       How can you set up just one negative charge to score a goal? (Remember to hit start) You can put a negative charge in the goal and the positive puck will eventually go towards it.

4.       Clear each time you try a new set up.  Reset if you want to retry your current set up.

5.       How can you set up just one positive charge to score a goal? You can put a positive charge behind the positive puck to push it away.

6.       Change the mass and see what happens.

7.       What happens when the mass is lighter? There is a collision!

8.       Why does the mass affect the speed if it is not apart of the electric force equation? Because if the mass is lighter, it will go faster than if it is heavier.  The mass can either hold it down or lighten it up.

9.       Reset – Put one positive charge on the surface and one negative charge directly below it.

10.   Check the “Field” box.

11.   Draw the field (you can connect the arrows if you wish)

12.   Set up a triangle of charges, with two positives and one negative.  Draw the field lines for this set up.

13.   Now play the game.  You can practice a little bit if you want.

14.   Set difficulty to 1, then 2, then 3.  When you beat each level, draw your set up, and show me.  Hint: leaving the field box checked might help you

Level 1 set up:

Level 2 set up:

Level 3 set up:

**After 3 hours of trying, I was unable to figure this one out!**  L

2. Work with any of the Chemistry Simulations to create your own Teaching Idea. The criteria for this is as follows:

a. must identify and meet three (3) science education standards

b. must be original work

c. must be scientifically accurate and appropriate for the directed grade level.

“Wave on a String” Interactive Simulation Teaching Idea

Standards Met:

Content Standard: Students in Wisconsin will understand that there are unifying themes: systems, order, organization, and interactions; evidence, models, and explanations; constancy, change, and measurement; evolution, equilibrium, and energy; form and function among scientific disciplines.

Content Standard: Students in Wisconsin will understand that science is ongoing and inventive, and that scientific understandings have changed over time as new evidence is found.

Content Standard: Students in Wisconsin will investigate questions using scientific methods and tools, revise their personal understanding to accommodate knowledge, and communicate these understandings to others.

Content Standard: Students in Wisconsin will demonstrate an understanding of the relationship between science and technology and the ways in which that relationship influences human activities.

Activity:

1.       Go to http://phet.colorado.edu/en/simulation/wave-on-a-string and click on “Run Now!”

2.       Once you load this simulation, make sure that the “damping” is set to “50” and the “tension” is set to “high.”  Also make sure that “manual” is checked and that “fixed end” is checked.

3.       Now, using your mouse, move the wrench up and down to get a feel for how the simulation works.

4.       What happens when you move the wrench really fast?  What happens when you move the wrench really slow?  What is the difference between the two waves?

5.       How can you make the waves wider?  How can you make the waves taller and skinnier?

6.       Now, experiment with the different ends available (fixed end, loose end, and no end).

7.       What are the differences between these different ends?  (Look at the reaction after you stop moving the wrench.)

## Wednesday, July 6, 2011

### Activity 7

Activity 7: Acids and Bases

Water is everywhere!  So, lets spend one more activity learning about one of the key aspects of water.  Water has the ability to dissociate (break apart from HOH (or H2O) into H+ ions and OH- ions).  We refer to solutions with lots of H+ ions as acids and solutions with lots of OH- ions as bases.  By adding chemicals with H+ ions acidic solutions can be made.  By adding chemicals with OH- ions basic solutions can be made.

1. Review the Content Slides Acids and Bases on the D2L site.

2. Complete the Teaching Idea “Concept Questions for Chemistry using PhET” posted by Trish Loeblein on the pH Scale simulation at PHET (http://phet.colorado.edu/en/simulation/ph-scale). On your blog post the answers with your scientific explanations from the “Clicker Questions pH Scale” posted by Trish.

1.       B. False.  The color of something can’t show what it is.  You can always color stuff by using dye.

2.       D.  More than one.  This would include B and C because they have a pH around 7 and 8.

3.       C.  I believe it is C because this solution looks like it has more molecules in it although it is difficult to tell.

4.       B.  This is because there is more of the OH- solution than the H3O+.

5.       D.  More than one.  This is because A and B both have a large amount of H3O+.

6.       A.  Increase the pH.  This is because when you add water, the acidity decreases.

7.       B.  Decrease the pH.  This is because when you add water, the basicity is decreased and the pH goes down.

8.       A.  ABC.  This is because you go up from 6.5 to 7.4 to 12.06.

9.       C.  BAC.  This is because of the levels of H3O+ and the levels of OH-.

10.   A.  Something was added that made the equilibrium shift left.  This is because the pH is more than 7.

3. Complete the Teaching Idea “Intro to Strong and Weak Acids and Bases” posted by Chris Bires on the Acid-Base Solutions simulation (http://phet.colorado.edu/en/simulation/acid-base-solutions) and post on your blog your data and answers to the questions posed.

Introduction to Strong and Weak Acids and Bases PhET Lab (rvsd 5/2011)

Introduction:

When you test your pool’s pH, what are you those little vials or paper strips telling you?  When you hear an acid called “strong” or “weak”, what do those terms refer to?  In aqueous solutions, compounds can exist as molecules (undissociated) or ions (dissociated).  When an acid or a base exists in solution nearly completely as dissociated ions, we refer to that acid or base as strong.  A weak acid or base will donate ions to the solution, but will remain primarily as undissociated molecules.

Notation:

Acids are abbreviated HA, with the H representing the proton (H+) the acid donates to the solution.  The A is referred to as the acidic anion (A-) that is left in solution as the proton is donated.

Strong Bases are abbreviated MOH, with the OH representing the hydroxide ion (OH-) the base donates to the solution.  The M is cation (M+) that is left in solution as the hydroxide is donated. .

Autoionization:

Even without any acid or base added a very small number of water molecules will form protons (H+) and hydroxide ions (OH-).  The protons will then form hydronium ions, the acid ion.

Procedure: PhET Simulations Ã  Play With Sims Ã  ChemistryÃ  Acid-Base Solutions Ã

The concentration of the acids and bases used in the  at 0.010 (10-2) Molar.

·         Begin with a strong acid and lower the pH probe into the beaker.  What is the pH of this solution?

·         Test this strong acid with both pH paper and the conductivity probe.  What color does the pH indicator become?  Is this strong acid an electrolyte?  Does current travel through this solution?

·         Repeat the above tests with the weak acid, the strong base, and the weak base, and water.  Collect your observations in the table below:

 Strong Acid Weak Acid Strong Base Weak Base Water pH meter read(value) 2.00 4.50 12.00 9.50 7.00 pH paper(color) 2 5 12 9 7 Conductivity(bright/dim/none) Bright Dim Bright Dim None Exists as Mostly (ions/molecules) Molecules Ions Molecules Ions Molecules

Procedure:

This simulation allows you to change the concentration of a strong and weak acid and base.

Complete the table below for some strong acids and bases and weak acids and bases by adjusting the concentration.

Strong Acids

 Strength Initial Acid Concentration (mol/L) [HA] (mol/L) [A-] (mol/L) [H+] (mol/L) pH .010 M Negligible 1.00 x 10-2 1.00 x 10-2 2.00 .050 M Negligible 5.00 x 10-2 5.00 x 10-2 1.30 .100 M Negligible 1.00 x 10-1 1.00 x 10-1 1.00 1.00 M Negligible 1.00 x 100 1.00 x 100 0.00

Weak Acids

 Strength (approximately) Initial Acid Concentration (mol/L) [HA] (mol/L) [A-] (mol/L) [H+] (mol/L) pH .015 M 1.50 x 10-2 3.19 x 10-5 3.19 x 10-5 4.50 .150 M 1.50 x 10-1 1.01 x 10-4 1.01 x 10-4 4.00 .015 M 4.75 x 10-4 1.45 x 10-2 1.45 x 10-2 1.84 .150 M 3.16 x 10-2 1.18 x 10-1 1.18 x 10-1 .93

Strong Bases

 Strength Initial Acid Concentration (mol/L) [MOH] (mol/L) [M+] (mol/L) [OH-] (mol/L) pH .010 M Negligible 1.00 x 10-2 1.00 x 10-2 12.00 .050 M Negligible 5.00 x 10-2 5.00 x 10-2 12.70 .100 M Negligible 1.00 x 10-1 1.00 x 10-1 13.00 1.00 M Negligible 1.00 x 100 1.00 x 100 14.00

Weak Bases

 Strength (approximately) Initial Acid Concentration (mol/L) [B] (mol/L) [BH+] (mol/L) [OH-] (mol/L) pH .015 M 1.50 x 10-2 1.37 x 10-5 1.37 x 10-5 9.14 .150 M 1.50 x 10-1 4.34 x 10-5 4.34 x 10-5 9.64 .015 M 2.80 x 10-4 1.47 x 10-2 1.47 x 10-2 12.17 .150 M 2.14 x 10-2 1.29 x 10-1 1.29 x 10-1 13.11

Conclusion Questions:

1.       A strong acid is very concentrated / exists primarily as ions.

2.       A weak base is a nonelectrolyte / weak electrolyte / strong electrolyte.

3.       A strong base is a nonelectrolyte / weak electrolyte / strong electrolyte.

4.       At the same concentration (Molarity) a strong acid will have a higher / lower / the same pH as a weak acid.

5.       As concentration of a weak acid increases, the pH increases / decreases / remains constant.

6.       As concentration of a weak base increases, the pH increases / decreases / remains constant.

7.       As the concentration of a weak acid increases, the number of ions increases / decreases / remains constant.

8.       As the concentration of a weak acid increases, conductivity increases / decreases / remains constant.

9.       As the strength of a weak acid increases, the proportion of ions to molecules increases / decreases.

10.   As the strength of a weak acid increases, the conductivity increases / decreases / remains constant.

11.   What are the pH values of a weak acid with a concentration of 0.10 and a strong acid with a concentration of 0.01, ten times lower?

Weak acid, 0.10 M = 4.0

Strong Acid, 0.01 M = 4.50

12.   Explain the significance of the results of your calculation above. The pH value goes up by .5 every time you move over one decimal place to the left.