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.
Tasks to be completed:
1. Choose any Teaching Idea from any of the Chemistry Simulations (http://phet.colorado.edu/en/simulations/category/chemistry ) and post your results/data and/or answers on your blog.

pH Scale Simulation

Go to my website and click

on the link to get to this

Simulation. Click Run, and

follow the procedure below.

1)         You need to get familiar with adjusting the amount of liquid in the beaker. Choose water from the pull down menu. Fill and drain the water using the faucet knobs above and below the beaker. Try to get 0.5 L of water in the beaker. Using the slide arrow, adjust the flow. Play for a bit! Be sure to click the box shown.

2)         Using the pull-down menu, change the contents of the beaker to “water”.

What is the pH? __7.00______

Record and compare (concentration mol/L) H₃O⁺/OH^- ratio.

Both are 1.00 x 10^-7

3)         Fill the beaker with drain cleaner.

What is the pH? __13.00______

Record and compare (concentration mol/L) H₃O⁺/OH^- ratio.

H₃O⁺ =1.00 x 10^-13

OH^-  = 1.00 x 10^-1

4)         Fill the beaker with soda.

What is the pH? __2.50______

Record and compare (concentration mol/L) H₃O⁺/OH^- ratio.

H₃O⁺= 3.16 x 10^-3

OH^-= 3.16 x 10^-12

5)         Using “custom liquid”, adjust the pH level to 6.00. How does the H₃O⁺/OH^- ratio differ from a pH of 7?

Record and compare (concentration mol/L) H₃O⁺/OH^- ratio.

With a pH of 6, H₃O⁺/OH^- are both 1.00 x 10^-6. With a pH of 7, H₃O⁺/OH^- are both 1.00 x 10^-7.

6)         Again, using “custom liquid, adjust the pH level to 8.00. How does the H₃O⁺/OH^- ratio differ from a pH of 7?

Record and compare (concentration mol/L) H₃O⁺/OH^- ratio.

With a pH of 8, H₃O⁺ is 1.00 x 10^-8 and OH^- is 1.00 x 10^-6. With a pH of 7, H₃O⁺/OH^- are both 1.00 x 10^-7.

7)         Alright…let’s mix some acid items with water to see what happens to the H₃O⁺/OH^- ratio!

8)         Fill the beaker with coffee (pH 5.0). Drain out half, and replace that amount with water. What is the new pH? ___5.30_____

 Record (concentration mol/L) H₃O⁺/OH^- ratio.

H₃O⁺ =5.01 x 10^-6

OH^-=2.00 x 10^-9

9)         OK, feeling nauseous? Fill er’ up with Barf!(pH 2.0) Drain out half, and replace it with H₂O!

What is the new pH?__2.31______

Record (concentration mol/L) H₃O⁺/OH^- ratio.

H₃O⁺= 4.90 x 10^-3

OH^-= 2.04 x 10^-12

10)       Let’s get back to “basics”. LOL.  Fill up with hand soap, drain half, and replace with water.

What is the new pH? __9.70______

Record (concentration mol/L) H₃O⁺/OH^- ratio.

H₃O⁺= 2.00 x 10^-10

OH^-= 5.01 x 10^-5

11)       What do you notice about the H₃O⁺/OH^- ratio when you add water to either an acid or a base? Hmmm….refer to how the mol/L changes.

When you add water to an acid, the pH goes up. When you add water to a base, the pH goes down.

12)       Calculate: Add anything to the beaker. Using your scientific calculator, find the negative logarithm (-log) of H₃O⁺ mol/L. This should match the pH value given. 

Blood pH=7.40

-log(3.98 x 10^-8)=7.40

13)       Calculate: Add anything to the beaker. Using your scientific calculator, find the negative logarithm (-log) of OH^- mol/L. This should match the pOH value given. 

Batter acid pH= 1.00

-log(1.00 x 10^-13)=13

2. Work with any of the Chemistry Simulations to create your own Teaching Idea. The criteria for this is as follows:
Enter the Build an Atom simulation at: http://phet.colorado.edu/en/simulation/build-an-atom
Begin the simulation. Make sure to click on all 3 green plus signs on the right-hand side in order to see the details. Choose and create 5 elements each from a different group (i.e. Halogens, Noble gases, etc.).
For each element:
Take screen shot of atom made with simulation.
Determine atomic number, mass number, and group they belong to.
Answer the following questions:
1. How do you change an atom from neutral to ionic?
2. What makes an atom stable/unstable?
3. Explain the differences in charge and location of protons, neutrons, and electrons.
4. How would you create an isotope?
Click on the Game tab in the upper left. Play the Game starting on Level 1 and working your way up to Level 4. Take a screen shot of your score after each level. Use this game to figure out what you need to study more and ask more questions about.
C.8.2 Identify data and locate sources of information including their own records to answer the questions being investigated
C.8.5 Use accepted scientific knowledge, models, and theories to explain their results and to raise further questions about their investigations
C.8.8 Use computer software and other technologies to organize, process, and present their data

Activity 7

Activity Tasks:

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, pH determines acidity, not color.
2. D. Because both B and C are above 7 so they are both basic.
3. C. Because there is a higher number of Hydrogen atoms.
4. B. Because there is a lower number of Hydrogen atoms.
5. D. Because both A and B have high levels of Hydrogen.
6. A. Because adding water will lessen the acidity, so the pH level goes up. 
7. B. Because adding water will lessen the basicity, so the pH level goes down, but not by 2. 
8. A. Because the numbers gradually get higher.
9. C.
10. A. Something was added to the spit to make its equilibrium shift to the left.
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.

Name:____________________

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

        How does the strength of an acid or base affect conductivity?pH?

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 à Play With Sims à Chemistryà Acid-Base Solutions à  

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 red	4 orange	11 blue	9 green	7 yellow
Conductivity (bright/dim/none)	bright	dim	bright	dim	none
Exists as Mostly (ions/molecules)	ions	ions	molecules	molecules	ions

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	55.6	2
	.050 M	Negligible	5.00 x 10^-2	55.6	1.30
	.100 M	Negligible	1.00 x10^-1	55.5	1
	1.00 M	Negligible	1.00 x10^0	54.6	0

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	4.20 x10^-5	55.6	4.38
	.150 M	1.50 x 10^-1	1.33 x10^-4	55.6	3.88
	.015 M	9.61 x10^-4	1.40 x10^-2	55.6	1.85
	.150 M	4.94 x10^-2	1.01 x10^-1	55.5	1.00

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 x10^-1	1.00 x10^-1	13.00
	1.00 M	Negligible	1.00 x10^0	1.00 x10^0	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	3.46 x 10^-5	3.46 x 10^-5	9.54
	.150 M	1.50 x 10^-1	1.10 x 10^-4	1.10 x 10^-4	10.04
	.015 M	2.33 x 10^-4	1.48 x 10^-2	1.48 x 10^-2	12.17
	.150 M	1.85 x 10^-2	1.32 x 10^-1	1.32 x 10^-1	13.12

Conclusion Questions:

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

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 :____2.0________