Exploration of Chemistry

Exploration of Chemistry

Balloons & Static Electricity

Go to Google and search “PhET Simulations”.  On the left side of the page, click on “Electricity, Magnets & Circuits.”  On the right side of the page, scroll down to find the “Balloons & Static Electricity” simulation.

Lab Questions:

Answer questions #1-3 using COMPLETE SENTENCES!!!

1.      Play with the simulation and observe what happens when the balloon is rubbed on the sweater.  Explain why this happens.   The balloon picks up the negative charges from the sweater and then it retracted from the wall to and attracted to the sweater.  

2.      The process you completed in #1 is a called charging an object by friction.  Bring your charged balloon near the wall and describe what happens to the wall.  Explain why this happens.   The negatives move away because they are not attracted to balloon negatives

3.      The effect you observed in the wall in #2 is called polarization.  Now, take your charged balloon and place it somewhere between the wall and the sweater.  Observe what happens, and describe it here.  Explain why this happens!   It moves towards the sweater because it is attracted to the positives from the sweater.

Post-Lab Questions: 

Write the letter of the correct answer on the blank provided.

__b___  1.     When charging an object by friction,

a.   only the positive charges move from one object to the other.

b.   only the negative charges move from one object to the other.

c.   both the positive and negative charges move from one object to the other.

d.   neither the positive nor the negative charges move from one object to the other.

___d__  2.     When an object becomes polarized,

a.   only the positive charges move within the object.

b.   only the negative charges move within the object.

c.   both the positive and negative charges move within the object.

d.   neither the positive nor the negative charges move within the object.

___b__  3.     Based upon what you saw in this lab, then, it can be said that

a.   positive charges are stationary within objects.

b.   negative charges are stationary within objects.

c.   positive charges are mobile within objects.

d.   negative charges are mobile within objects.

e.   both a and b

f.    both a and d

g.   both b and c

h.   both c and d

John Travoltage

Go to Google and search “PhET Simulations”.  On the left side of the page, click on “Electricity, Magnets & Circuits.”  On the right side of the page, scroll down to find the “John Travoltage” simulation.

Lab Questions:

Answer questions #1-3 using COMPLETE SENTENCES!!!

1.      Rub John Travoltage’s foot on the carpet and observe what happens.  What is this called?  ­­­­­­­­­­­­­­­­­This is called friction.  Where have you seen this before? I have seen this in the balloon activity.  Explain why this happens.  (Use a COMPLETE SENTENCE!)  When the foot is rubbed the positive charges are transferred to his body from the carpet.

2.      Watch after you stopped rubbing John Travoltage’s foot on the carpet, what happened to the charges in his body?  They stopped moving and spread out.  Were the charges in his body positive or negative?   The charges in his body are negative. Explain why the charges do what they did.  (Use a COMPLETE SENTENCE!)  When the leg is moving the charges are gaining power or energy and when the leg stops the power supply stops and they stand still.

3.      Now, touch John Travoltage’s hand to the door knob.  Observe what happens.  Explain why this happens. (Use a COMPLETE SENTENCE!)  It gives him a shock because the negative charges are released from his body when they are connecting to a positively charged object such as the door knob.

Post-Lab Questions: 

Write the letter of the correct answer on the blank provided.

__c___  1.      Over time, all the negative charges in an object,

a.   remain clustered together where they were placed.

b.   spread out over a small area on the object.

c.   spread out over a large area on the object.

__b___  2.     When a charged object touches a conductor,

a.   the positive charges move to the conductor and exit the object.

b.   the negative charges move to the conductor and exit the object.

c.   both the positive and negative charges move to the conductor and exit the object.

d.   neither the positive nor the negative charges move to the conductor and exit the object.

__b___  3.     Based upon what you saw in this lab, then, it can be said that

a.   a person cannot be shocked if they have an excess charge on them.

b.   a person cannot be shocked if they have neutral charge.

c.   a person can be shocked at any time because it doesn’t depend on the charge the person has.

Part 2

Simulation name: Balancing chemical equations.

Science education standards

• C.4.4 Use simple science equipment safely and effectively, including rulers, balances, graduated cylinders, hand lenses, thermometers, and computers, to collect data relevant to questions and investigations
• C.4.6 Communicate the results of their investigations in ways their audiences will understand by using charts, graphs, drawings, written descriptions, and various other means, to display their answers
• D.4.5 Construct simple models of what is happening to materials and substances undergoing change, using simple instruments or tools to aid observations and collect data

Grade level: 4^th grade

Lesson on balancing chemical equations

Worksheet with pHet stimulations http://phet.colorado.edu/en/simulation/balancing-chemical-equations

Name: ___________________________                                                 Date________________

11.      Balance the equation for Ammonia

a.       ___N2 + ___ H2 = ___NH3

b.      Draw what the balance scales look like.

22.      Separate the water molecule

a.       ___H2O = ___H2 + ___O2

b.      Draw what the balance scales look like.

33.      Combust Methane by making it a balance equation

a.       ___ CH4 + ___ O2 = ___CO2 + ___H2O

b.      Draw what the balance scales look like

44.       Click on the Balancing game tab and play until at least level one is completed.  

55.       Why do chemical equations need to be balanced? ________________________________ _______________________________________________________________________________________________________________________

66.       What choice is the chemical equation for Calcium chloride? Circle your answer.

a.       Ca3Cl6

b.      Ca4Cl

c.       CaCl2

d.      Ca6Cl5

77.       What does the chemical equation for Carbon Dioxide look like? ____________________ _____________________________________________________________________________________________________________________.

Acids and Bases

Acids and Bases

1. B.  False because the color does not tell whether it is an acid or base it is the pH scale level.
2. D. More than one is basic because two of them have a higher pH level than 7.0.
3. C. Just the one because it has more levels H30+ than the other ones.
4. B. this one is basic because the hydrogen atoms powers need to be over 7.
5. D. A and B both have higher levels of H
6. A. Adding water would increase the pH because the water lessens the acidity. More water lessens the acidity, so pH goes up.
7. B. the pH decreases when water is added resulting in a lower number. more water lessens the basicity, so pH goes down, from 10 to 9.7, but not by 2 .
8. A. A, B, C because the closer the number is to zero the more acid it is and the closest is it to 14 the more basic it is.
9. C. B, A, C because looking at the powers that the numbers have they are increasing.
10. A. Something was added that made the equilibrium shift left. 

Name:__Emily Minniecheske____

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 pH	4.5 pH	12.00 pH	9.50 pH	7.00 pH
pH paper (color)	2 red	5 orange	11 blue	9 green	7 yellow
Conductivity (bright/dim/none)	bright	dim	bright	dim	none
Exists as Mostly (ions/molecules)	ions	molecules	ions	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
Strong	.010 M	negligible	1.00x10^-2	1.00x10^-2	2
Strong	.050 M	negligible	5.00x10^-2	5.00x10^-2	1.3
Strong	.100 M	Negligible	1.00x10^-1	1.00x10^-1	1
strong	1.00 M	negligible	1.00x10^0	1.00x10^0	0

Weak Acids

Strength (approximately)	Initial Acid Concentration (mol/L)	[HA] (mol/L)	[A-] (mol/L)	[H+] (mol/L)	pH
lower	.015 M	1.5x10^-2	3.87x10^-5	3.87x10^-5	4.41
lower	.150 M	1.5x10^-1	1.22x10^-4	1.22x10^-4	3.91
higher	.015 M	1.93x10^-4	1.48x10^-2	1.48x10^-2	1.83
higher	.150 M	1.58x10^-2	1.34x10^-1	1.34x10^-1	.87

Strong Bases

Strength	Initial Acid Concentration (mol/L)	[MOH] (mol/L)	[M+] (mol/L)	[OH-] (mol/L)	pH
strong	.010 M	negligible	1.00x10^-2	1.00x10^-2	12
strong	.050 M	Negligible	5.00x10^-2	5.00x10^-2	12.7
strong	.100 M	Negligible	1.00x10^-1	1.00x10^-1	13
strong	1.00 M	negligible	1.00x10^0	1.00x10^0	14

Weak Bases

Strength (approximately)	Initial Acid Concentration (mol/L)	[B] (mol/L)	[BH+] (mol/L)	[OH-] (mol/L)	pH
lower	.015 M	1.49x10^-2	9.74x10^-5	9.74x10^-5	9.99
lower	.150 M	1.50x10^-1	3.09x10^-4	3.09x10^-4	10.49
strong	.015 M	1.64x10^-4	1.48x10^-2	1.48x10^-2	12.17
strong	.150 M	1.38x10^-2	1.36x10^-1	1.36x10^-1	13.13

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 :_6___________ Strong Acid, 0.01 M :___2_________

12.  Explain the significance of the results of your calculation above.  The stronger acid has a lower pH because there are more ions.