PhET/C2/pH-Scale/English

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Visual Cue Narration
Slide Number 1

Title slide

Welcome to this Spoken tutorial on pH scale using interactive PhET simulation.
Slide Number 2

Learning Objectives

In this tutorial 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.

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 learn to-

Determine whether a given solution is an acid or a base.

Arrange acids and bases according to their strength.

Determine the concentration of hydroxide ion, hydronium ion and water at a given pH.

Slide Number 6

Learning Goals

Using this simulation we will learn about,

pH of a solution.

Effect of dilution on pH of a solution.

Logarithmic and Linear scale.

Slide Number 7

pH scale

pH scale is a, numeric scale used to specify the acidity or basicity of an aqueous solution.

pH is a measure of hydrogen ion concentration in mol/L.

Slide Number 8

Formula for pH calculation.

Point to the formula.

pH = - log[H+]

pH is negative logarithm to base 10 of hydrogen ion concentration.

pH = - log[H+]

Slide Number 9

pH for Acids, Bases and Neutral Solutions.

For Acidic solutions, pH is less than 7(< 7).

For Basic solutions, pH is greater than 7 (> 7).

For Neutral solutions, pH is equal to 7 (= 7).

Slide Number 10

Link for PhET simulation

point to

http://phet.colorado.edu

Use the given link to download the simulation.

http://phet.colorado.edu

Point to the file in Downloads folder. I have already downloaded the pH Scale PhET, to my Downloads folder.
Right click on ph-scale html file.

Click on Open With Firefox Web Browser.

To open the simulation, right click on ph-scale html file.

Choose the option Open With Firefox Web Browser.

The file opens in the Browser.

Cursor on the interface. This is the interfaceof pH scale simulation.
Point to the each screen. The interface has three screens-

Macro

Micro

My solution

Cursor on the Macro screen.

Click on Macro screen.

Let us begin our simulation with Macro screen.

Click on Macro screen to open it.

Cursor on Macro screen.

Cursor on a pH scale.

Point to a green probe.

Point to a pH meter.

This screen has-

A pH scale on the left, to display pH range from 0 to 14.

A green probe attached to pH scale to measure pH and

A pH meter to show pH of the liquids.

Cursor on water pump.

Cursor on water container.

Point to pump.

A Water pump on the right side of screen to add water.

A Graduated water container filled by default with Chicken Soup.

A pump to remove solution is attached at the bottom left of the container.

Point to the Dropper.

Cursor on Drop down box.


Point to Chicken Soup.

A Dropper to add liquid.

A Drop down box to choose one of the liquids.

By default Chicken Soup is selected.

Point to Reset Button. A Reset Button is provided at the right hand side bottom corner.
Click on the drop down arrow.

Scroll to Battery Acid and click.

Point to the container.

Point to 0.5 L.

Click on the drop down arrow.

Scroll to Battery Acid and click on it.

Notice that, the container is filled with Battery Acid up to 0.50 L (0.5litres).

Drag the green probe.

Point to the pH meter.

Drag the green probe into the container and Observe the pH.

Meter shows the pH value as 1.0.

As pH is less than 7(<7), Battery Acid is an acidic solution.

Click on water pump.

Point to the container.


Cursor on the pH meter.

Now click on the water pump to add more water.

Increase the water level up to 1Litre.

Observe the change in pH on addition of water.

Now pH meter shows pH value as 1.30.

Point to pH meter. Notice that pH of Battery Acid increases on addition of water.

This is because hydrogen [H+] ion concentration decreases with dilution.

Now we will select another solution.
Click on drop down arrow.

Scroll and click on Hand Soap.

Point to the container.

Click on drop down arrow.

Scroll to Hand Soap and click on it.

Container is filled with Hand Soap solution.

Point to the pH meter. Here, pH meter shows the value of pH as 10.00.

This indicates that Hand Soap is basic in nature.

Click on water pump. Click on water pump to add water to Hand Soap solution.
Click on water pump.

Cursor on the pH meter.

For 1 L, Hand Soap solution shows a pH value of 9.70.

We can see that pH of Hand Soap solution decreases on dilution.

This is because hydroxide ion (OH- ) concentration decreases with dilution.

Click on bottom pump.


Click on dropper.


Point to the pH meter.

Click on the bottom pump to remove half litre of Hand Soap solution.

Click on the dropper and increase the level of Hand Soap solution to 0.6 L.

Notice the change in pH.

It increases as concentration of hydroxide ion (OH- ) increases.

Now we will arrange the acids and bases according to their strengths.
Click on drop down arrow.

Click on Blood.

Point to the container and 0.5 L.


Point to the pH meter.

For that we will check the pH of different liquids.

Click on drop down arrow and select Blood.

Container is filled with Blood up to 0.50 L.

Meter shows the pH value as 7.40.

As pH is greater than 7( >7), Blood is a basic solution.

Click on drop down arrow.

Click on Orange Juice.

Point to the pH meter and 0.50 L.

Again click on drop down arrow and select Orange Juice.

Meter shows pH value as 3.50 for 0.50 L.

It is clear that Orange Juice is an acidic solution.

Slide Number 11

pH of acids and bases.

According to the above pH values the order is as follows.

Hand soap > Blood > Orange Juice> Battery Acid.

Slide Number 12

Assignment

As an assignment,

Check the pH of each liquid.

And arrange the liquids according to the pH range.

Point to the Micro screen.

Click on the Micro screen.

Now, we will move on to Micro screen.

Click on Micro screen at the bottom of the interface.

Cursor on the screen.

Point to pH scale.

Point to Concentration and Quantity switch.

Point to and click on -ve red button.

Point to Logarithmic and Linear switch.

This screen has the following tools-

A pH scale on the left hand side of screen.

A switch on the top of pH scale to select between Concentration and Quantity.

A red button with a minus(-) to hide pH scale.

A switch at the bottom to select between Logarithmic and Linear scale.

Point to Check boxes.


Point to and click on -ve red button.

Check boxes to select-

Hydronium ion to hydroxide ion ratio (H30+/OH- ) and Molecule count.

In the pH meter, a red button with a minus(-) to hide pH reader and value.

Click on drop down arrow.

Scroll and click on Soda Pop.

Point to the container.

Click on the drop down arrow and select Soda Pop.

Container is filled with Soda Pop.

Point to pH meter. pH meter shows pH value as 2.50.

It means, Soda Pop is an acidic solution.

Point to pH scale 3.2 x 10-3.

Point to pH scale 3.2 x 10-12.

As Soda Pop is acidic,

Concentration of hydronium ion is high and hydroxide ion is low.

Click on Quantity switch.

Point to (5.0 x 10-3)

Point to (5.0 x 10-13) and

point to (28).

Then click on Quantity(mol),

we will see the number of moles of hydronium ion, hydroxide ion and water.

Point to Linear.

Click on Linear.

Point to pH scale.

Let us change Logarithmic scale to Linear.

To do so click on Linear .

The pH scale changes to Linear mode.

We also see that pH values become Linear.

But we will not use Linear scale as

pH is in Logarithmic scale.

Click on H30+/OH- ratio check box.


Point to container.

Point to red dots.

Point to blue dots.

Click on Hydronium ion to hydroxide ion ratio (H30+/OH-) check box.

A large number of red dots are seen in the container.

These are hydronium ions.

A few blue dots that are seen are hydroxide ions (OH- ).

Click on Molecule Count check box.

Point to 9.52 x 1020.

Point to 9.52 x 1012.

Point to 1.66 x 1025.

To see count of molecules in Soda Pop, click on Molecule count check box.

Count of hydronium ions, hydroxide ions and water molecules in Soda Pop is seen.

Click on water pump.

Point to H30+, OH- and H20.

Point to pH meter.

Let us see how dilution affects the number of molecules.

Click on water pump, fill the container up to 1 L.

Observe the change in Molecule Count.

Note the increase in pH value.

pH becomes 2.80.

Slide Number 13

Assignment

As an assignment,

Measure the pH of Blood sample.

Observe the change in Molecule Count and H30+/OH- ratio after dilution.

Point to My Solution screen.


Click on My Solution screen.

Now, we will move on to 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 tools as that of Macro and Micro screens.
Point to the Graduated container.


Point to the pH meter.

This screen also has some additional tools.

A Graduated container on the right hand side of screen.

A pH meter to adjust pH directly.

Point to the screen. This screen allows direct manipulation of pH or ion concentration.
Click and move H30+and OH- slider.


Click on Black Arrow upwards or downwards.

In this screen, we can make a solution of our choice in two ways-

By moving the H30+or OH- slider on pH scale.

By clicking black arrow upwards or downwards.

Move the (H30+) slider.


Point to OH- slider.

Let us move the hydronium ion (H30+) slider upwards.

Notice that, simultaneously Hydroxide ion(OH-) slider also moves downwards.

Click on black arrow downwards. Let's make a solution of pH 4.0 by clicking the black arrow downwards.

This is an acidic solution.

Click on H30+and OH- ratio check box.

Click on Molecule count check box.


Point to 3.01 x 1019.

Now, Click on Hydronium ion to hydroxide ion (H30+/OH- )ratio and Molecule count check boxes.

Notice that Molecule count for hydronium ion (H30+) is 3.01 x 1019.

Slide Number 14

Assignment

As an assignment,

Make solutions of pH 7.0 and 9.0.

Observe and compare the change in molecules.

Slide Number 15

Summary

Let us summarize.

In this tutorial we have learnt about,

interactive PhET simulation, pH scale.

Slide Number 16

Summary I

Using this simulation we have learnt to-

Determine whether a given solution is an acid or a base.

Arrange acids and bases according to their strength.

Determine the concentration of hydronium ion, hydroxide ion and water at a given pH.

Slide Number 17

Summary II

pH of a solution.

Effect of dilution on pH of solution.

Logarithmic and Linear scale.

Slide Number 18

About Spoken Tutorial project

The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

Slide Number 19

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 20

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.


Please post your timed queries in this forum.
Slide Number 21

Acknowledgement

This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
Slide Number 22

Acknowledgement

Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at

this link.

This is Meenal Ghoderao from IIT Bombay.

Thank you for joining.

Contributors and Content Editors

Madhurig, Meenalghoderao