ChemCollective-Virtual-Labs/C2/Buffer-Solutions/English
Visual cue Narration Slide Number 1 Title slide Welcome to this tutorial on pH scale using interactive PhET simulation. Slide Number 2 Learning objectives we will learn- How to use interactive PhET simulation, pH scale. Slide Number 3 Pre-requisites To follow this tutorial, Learners should be familiar with topics in high school science subject. Slide Number 4 System Requirements Here I am using- Ubuntu linux OS version 14.04 Java version 1.7.0 Firefox Web Browser version 53.02.2 Slide Number 5 Learning Goals Using this simulation we will be able to learn- pH of solution Determine acidity or basicity of solution on the basis of pH Place acids and bases in relative order. Effect of dilution on pH of solution. Logarithmic and linear scale. Determine the concentarion of hydroxide, hydronium and water at a given pH Slide Number 6 pH of solution. PH scale - It is numeric scale used to specify the acidity or basicity of an aqueous solution. PH is a measure of hydrogen ion concentration in mol/L.
PH is the negative logarithm of base 10 of hydrogen ion concentration. from the definition pH can be written as, pH = - log[H+]
For acidic solution, pH < 7 Ex: Hcl(10-2) will have a pH = 2 For basic solution, pH > 7 Ex: NaOH(10-12) will have a pH=12 For neutral solution, pH = 7
Slide Number 7
Link for PhET simulation
http://phet.colorado.edu pH simulation is given as code file along with this tutorial.
Use the given link to download
http://phet.colorado.edu Cursor on the interface. This is the interface for pH simulation Point to each screen. The interface has three screens- Macro Micro My solution
Cursor on Macro screen.
Let us begin our simulation with Macro screen. Click on Macro screen to open it. Cursor on Macro screen. Cursor on pH scale. Point to green probe.
Point to pH meter.
This screen has-
pH scale at the left of screen.
Green probe attached to pH scale ro measure pH.
PH meter to show pH.
Cursor on water pump.
Cursor on water canter.
Point to pump.
Water pump at the right of screen to add water.
Water canter with tap for the solution .
Pump to remove solution attached to right bottom of the canter.
Point to Dropper.
Cursor on Drop Downbox. Dropper at the top of the container to add more liquid. At the top middle of screen has Drop Downbox to choose one of the liquid.
Point to Reset Button. A Reset Button is provided at the right hand side bottom corner.
Click on Black arrow.
cursor on Battery acid and click
Point to canter. Point to dropper
By default chicken soup is selected. Click on black arrow of Drop down box,go to Battery Acid. Click on it. Notice that canter is filled with Battery acid to 1/2 L. If we want more liquid click on red button of dropper and press it. Click and drag probe. Click on green prob and drag into canter liquid.
Point to pH meter. Observe the pH value. Battery acid shows the pH=1.0 It is clear that Battery Acid is acidic solution. Click on water pump.
Point to pH meter.
Cursor on pH meter. Now click on the water pump to add more water that is 1L. Observe the change in pH of solution with addition of more water. Now pH meter shows the pH=1.51 Point to pH meter. We can see that pH of Battery acid increases with addition of water.
This is because concentration of [H+] ion decreases which causing the acidity.
It is clear that with the dilution of acidic soultion - pH of acidic solution increases. Acidity of acidic solution decreases and it aprroaches to neutral. Click on Dropdown box arrow. Go to and click hand soap. Now click on black arrow of Dropdown box,go to hand soap and click on Hand Soap. Point to pH meter. For 1/2 L, pH meter shows the value of pH=10.0. Click on water pump.
Point to pH meter. Click on water pump to add more water to hand soap. Notice the decrease in pH of Hand soap with addition of water. Cursor on pH meter. For 1.04 L,Hand soap shows pH=9.66 we can see that pH of Hand soap decreases with dilution with water.
This is because concentration of [OH-] decreases with dilution.
It is clear that with the dilution of basic solution- pH of basic solution decreases Basicity of basic solution decreases and it aprroaches to neutral. Click on solution pump.
Click on Dropper. Point to pH meter. Now click on lower solution pump to remove some hand soap solution. Again click on dropper to add more hand soap. We will see that again pH inceraes as concentration of [OH-]increases.
Click on drop down box. Cursor on spit. point to pH meter. Now ,we will check the pH of some liquids. Click on black arrow of drop down box and select spit. Meter shows the pH=7.40 Spit is basic liquid. Click on dropdown box. Cursor on milk Point to pH meter. Click on black arrow of dropdown box and select milk Meter shows pH=6.50 It is clear that milk is acidic liquid. Assignment Assignment- Check the pH for each liquid and arrange them in proper acidic and basic solutions. Click on Micro screen. Now,we will move to the Micro screen. Click on Micro screen at the bottom of the interface.
Point to pH scale.
Point to concentration switch.
Point to logarithmic switch.
Point to -ve red button. Left side of screen has the following tools-
pH scale at the left hand side of screen. Switch to select between concentration and quantity at the top of scale. switch to select between logarithmic and linear scale at the bottom of scale. -ve red button to hide pH scale.
Point to Checkbox.
Point to -ve red button. Right side of screen have the following tools- Checkbox to select H30+/OH- ratio and molecule count. -ve red button to hide pH. Click on black arrow. Go to and click on Soda Pop. Now,click on black arrow of dropdown box to select liquid. Go to drop down box and click on Soda Pop. Point to pH meter We will see that for 1/2 L pH meter shows Ph=2.50. It means that Soda Pop is acidic solution.
Point to pH scale 3.2x10^-3 Point to pH scale 3.2 x 10^-12 As Soda Pop is acidic we will see that- Concentration of H30+ is high and OH- is low. Click on quantity switch. Point to H30+, OH- and H20.
If we click on quantity(mol), we will see the number of moles of H30+(5.0X10^-3),OH-(5.0 x 10^-13) and H20(28).
Click on linear. Point to pH scale. We can switch the logarithmic scale to linear. click on linear . We will see the pH scale in linear mode. To bring the pH scale again in logarithmic mode, click on logarithmic mode. Click on H30+/OH- ratio check box. Point to canter . Now click on H30+/OH- ratio check box. Canter contains large numbers of H30+ ions indicated by red dots. Less number of Blue dot indicate number of OH- ion. Click on molecule count check box.
point to 9.52 x 10^20 point to 3.79 x 10^12 point to 3.31 x 10^25 To see the number of molecules in Soda Pop, click on molecule count check box. It will show number H30+, OH- and H20 molecules present in Soda Pop.
Click on water pump.
Point to H30+, OH- and H20.
Point to pH meter.
Now we will see how dilution affects the number of molecules.
Click on water pump,fill the canter upto 1L.
Observe the change in H30+/OH- ratio and molecule count.
Blue dots increases that means number of molecules of OH- increases.
PH is also increases, Ph meter shows the pH=2.80.
Assignment.
As an assignment ,
Measure the pH of blood sample.
Observe the change in molecule count and H30+/OH- ratio after dilution.
Click on My Solution screen.
Now,we will move to the My Solution screen.
Click on My Solution screen at the bottom of the interface.
Point to My Solution screen.
My Solution screen has the same tool as that of Macro and Micro screen.
Point to Graduated Beaker.
point to pH meter. This screen has additional tool as- Graduated beaker at left hand side of screen.
PH meter to adjust pH directly.
Point to My Solution screen. This screen allows directly manipulate pH or ion concentration.
Point to H30+and OH- slider.
point to Black Arrow.
In this screen we can make solution of our choice in two ways-
By moving the H30+and OH- slider
By pressing black arrow upward and downward.
Point to H30+and OH- slider.
Observe that H30+and OH- sliders moves simultaneously.
Point to pH meter.
Let's select pH 4.12 that is acidic solution for 1/2L.
Click on H30+and OH-ratio check box.
Click on molecule count check .
point to 2.29 x 10^19
point to 3.97 x 10^25 Click on H30+and OH- ratio and molecule count check box. we will see that number of H30+molecules (red dots)large in number. OH- molecules (blue dots)small in number.
Point to H30+ slider. point to pH meter. Now we will make basic solution. move the H30+ slider downwards. PH shows th value pH=11.81
Point to 4.72 x 10^11
point to 1.92 x 10^21 Now we will see that number of, H30+molecules (red dots)small in number. OH- molecules (blue dots)large in number. Point to 1.66 x 10^25 In both the cases the number of molecules of water remais the same.
Point to pH meter.
Point to 3.01 x 10^16
Now we will make neutral solution. Click on arrow to set the pH value=7. In this case we will see that, The number of H30+(Red dots) and OH- (blue dots) are the same. Slide Assignment. Assignment- Make a solution of pH of your choice and obseve the change in molecules. Slide Summery In this simulation we have learn about interactive PhET simulation,pH scale. Slide Summery In this simulation we have learnt- pH of solution Determine the solution is acidic or basic on basis of pH Place acids and bases in relative order. Effect of dilution on pH of solution. Logarithmic and linear scale. Determine the concentarion of hydroxide, hydronium and water at a given pH Slide Number13: About Spoken Tutorial project The video at the following link summarizes the Spoken Tutorial project. Please download and watch it. Slide Number14: Spoken Tutorial workshops The Spoken Tutorial Project team: conducts workshops using spoken tutorials and gives certificates on passing online tests. For more details, please write to us. Slide Number 15: Forum for specific questions: Do you have questions in THIS Spoken Tutorial? Please visit this site Choose the minute and second where you have the question. Explain your question briefly Someone from our team will answer them. Slide Number 16 Forum for specific questions: The Spoken Tutorial forum is for specific questions on this tutorial Please do not post unrelated and general questions on them This will help reduce the clutter With less clutter, we can use this discussions as instructional material. Slide Number 17: Acknowledgement Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. More information on this mission is available at
this link.
