PhET/C2/pH-Scale/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to this Spoken tutorial on pH scale using interactive PhET simulation. |
| 00:08 | In this tutorial, we will learn how to use interactive PhET simulation, pH scale. |
| 00:15 | To follow this tutorial,learners should be familiar with topics in high school science. |
| 00:22 | Here I am using-
Ubuntu Linux OS version 14.04 Java version 1.7.0 Firefox Web Browser version 53.02.2. |
| 00:38 | Using this simulation, we will learn to-
1. Determine whether a given solution is an acid or a base. |
| 00:49 | 2. Arrange acids and bases according to their strength
3. Determine the concentration of hydroxide ion, hydronium ion and water at a given pH. |
| 01:01 | Using this simulation, we will learn about:
4. pH of a solution 5. Effect of dilution on pH of a solution 6.Logarithmic and Linear scale. |
| 01:16 | pH scale is a numeric scale used to specify the acidity or basicity of an aqueous solution. |
| 01:25 | pH is a measure of hydrogen ion concentration in mol/L. |
| 01:30 | pH is negative logarithm to base 10 of hydrogen ion concentration.
pH = - log[H] |
| 01:37 | For acidic solutions, pH is less than 7(< 7). |
| 01:42 | For basic solutions, pH is greater than 7 (> 7). |
| 01:47 | For neutral solutions, pH is equal to 7 (= 7). |
| 01:52 | Use the given link to download the simulation. |
| 01:57 | I have already downloaded the pH Scale PhET, to my Downloads folder. |
| 02:02 | To open the simulation, right-click on ph-scale html file. |
| 02:08 | Choose the option Open With Firefox Web Browser. The file opens in the browser. |
| 02:16 | This is the interface of pH scale simulation. |
| 02:20 | The interface has three screens-
Macro Micro My solution |
| 02:27 | Let us begin our simulation with Macro screen. Click on Macro screen to open it. |
| 02:36 | This screen has-
A pH scale on the left, to display pH range from 0 to 14. |
| 02:44 | A green probe attached to pH scale, to measure pH and A pH meter to show pH of the liquids. |
| 02:54 | A water pump on the right side of screen to add water. |
| 02:59 | A graduated water container filled by default, with Chicken Soup. |
| 03:05 | A pump to remove solution is attached at the bottom left of the container. |
| 03:11 | A dropper to add liquid. |
| 03:14 | A drop down box to choose one of the liquids. By default, Chicken Soup is selected. |
| 03:22 | A Reset button is provided at the right hand side bottom corner. |
| 03:28 | Click on the drop-down arrow. |
| 03:31 | Scroll to Battery Acid and click on it. Notice that the container is filled with Battery Acid up to 0.50 L (0.5 litres). |
| 03:42 | Drag the green probe into the container and observe the pH. |
| 03:48 | Meter shows the pH value as 1.0. As pH is less than 7(<7), Battery Acid is an acidic solution. |
| 03:58 | Now click on the water pump to add more water. |
| 04:03 | Increase the water level up to 1 Litre. Observe the change in pH on addition of water.
Now pH meter shows pH value as 1.30. |
| 04:16 | Notice that pH of Battery Acid increases on addition of water.
This is because hydrogen [H] ion concentration decreases with dilution. |
| 04:28 | Now we will select another solution. |
| 04:32 | Click on drop down arrow. |
| 04:34 | Scroll to Hand Soap and click on it. Container is filled with Hand Soap solution. |
| 04:42 | Here, pH meter shows the value of pH as 10.00. This indicates that Hand Soap is basic in nature. |
| 04:54 | Click on water pump to add water to Hand Soap solution. |
| 04:59 | For 1 L, Hand Soap solution shows a pH value of 9.70. |
| 05:06 | We can see that pH of Hand Soap solution decreases on dilution. |
| 05:12 | This is because hydroxide ion (OH) concentration decreases with dilution. |
| 05:18 | Click on the bottom pump to remove half litre of Hand Soap solution. |
| 05:24 | Click on the dropper and increase the level of Hand Soap solution to 0.6 L. Notice the change in pH. |
| 05:34 | It increases as concentration of hydroxide ion (OH) increases. |
| 05:39 | Now we will arrange the acids and bases according to their strengths. |
| 05:45 | For that, we will check the pH of different liquids. |
| 05:50 | Click on drop down arrow and select Blood. Container is filled with Blood up to 0.50 L. |
| 05:59 | Meter shows the pH value as 7.40. As pH is greater than 7( >7), Blood is a basic solution. |
| 06:09 | Again click on drop down arrow and select Orange Juice. |
| 06:14 | Meter shows pH value as 3.50 for 0.50 L. It is clear that Orange Juice is an acidic solution. |
| 06:26 | According to the above pH values the order is as follows.
Hand soap > Blood > Orange Juice > Battery Acid. |
| 06:38 | As an assignment,
Check the pH of each liquid. And, arrange the liquids according to the pH range. |
| 06:48 | Now, we will move on to Micro screen. Click on Micro screen at the bottom of the interface. |
| 06:57 | This screen has the following tools-
A pH scale on the left hand side of screen, |
| 07:04 | A switch on the top of pH scale to select between Concentration and Quantity,
A red button with a minus(-) to hide pH scale, |
| 07:16 | A switch at the bottom to select between Logarithmic and Linear scale. |
| 07:22 | Check boxes to select-
Hydronium ion to hydroxide ion ratio (H30+/OH- ) and Molecule count, |
| 07:30 | In the pH meter, a red button with a minus(-) to hide pH reader and value. |
| 07:38 | Click on the drop down arrow and select Soda Pop.
Container is filled with Soda Pop. |
| 07:46 | pH meter shows pH value as 2.50. It means, Soda Pop is an acidic solution. |
| 07:54 | As Soda Pop is acidic, concentration of hydronium ion is high and hydroxide ion is low. |
| 08:02 | Then click on Quantity(mol). |
| 08:05 | We will see the number of moles of hydronium ion, hydroxide ion and water. |
| 08:12 | Let us change Logarithmic scale to Linear. To do so, click on Linear . |
| 08:20 | The pH scale changes to Linear mode. We also see that pH values become Linear. |
| 08:28 | But we will not use Linear scale as pH is in Logarithmic scale. |
| 08:34 | Click on Hydronium ion to hydroxide ion ratio (H30+/OH-) check box. |
| 08:39 | A large number of red dots are seen in the container. These are hydronium ions. |
| 08:46 | A few blue dots that are seen are hydroxide ions(</sup>/OH-). |
| 08:51 | To see count of molecules in Soda Pop, click on Molecule count check box. |
| 08:57 | Count of hydronium ions, hydroxide ions and water molecules in Soda Pop is seen. |
| 09:05 | Let us see how dilution affects the number of molecules. |
| 09:10 | 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. |
| 09:25 | As an assignment, measure the pH of Blood sample. |
| 09:30 | Observe the change in Molecule Count and H30+/OH- ratio after dilution. |
| 09:37 | Now, we will move on to My Solution screen. Click on My Solution screen at the bottom of the interface. |
| 09:46 | My Solution screen has the same tools as that of Macro and Micro screens. |
| 09:53 | This screen also has some additional tools: |
| 09:57 | a graduated container on the right hand side of screen, a pH meter to adjust pH directly. |
| 10:05 | This screen allows direct manipulation of pH or ion concentration. |
| 10:11 | In this screen, we can make a solution of our choice in two ways-
1. By moving the H30+or OH- slider on pH scale, 2. By clicking black arrow upwards or downwards. |
| 10:28 | Let us move the hydronium ion (H30+) slider upwards. |
| 10:32 | Notice that, simultaneously Hydroxide ion (OH-) slider also moves downwards. |
| 10:38 | Let's make a solution of pH 4.0 by clicking the black arrow downwards. This is an acidic solution. |
| 10:48 | Now, click on Hydronium ion to hydroxide ion (H30+/OH-) ratio and Molecule count check boxes. |
| 10:55 | Notice that Molecule count for hydronium ion (H30+) is 3.01 x 1019. |
| 11:01 | As an assignment,
make solutions of pH 7.0 and 9.0. Observe and compare the change in molecules. |
| 11:13 | Let us summarize.
In this tutorial, we have learnt about interactive PhET simulation, pH scale. |
| 11:22 | Using this simulation, we have learnt to-
1.Determine whether a given solution is an acid or a base. |
| 11:31 | 2. Arrange acids and bases according to their strength. |
| 11:36 | 3. Determine the concentration of hydronium ion, hydroxide ion and water at a given pH |
| 11:43 | 4. pH of a solution
5. Effect of dilution on pH of solution 6. Logarithmic and Linear scale. |
| 11:53 | The video at the following link summarizes the Spoken Tutorial project. Please download and watch it. |
| 12:02 | The Spoken Tutorial Project team:
Conducts workshops using spoken tutorials and gives certificates on passing online tests. For more details, please write to us. |
| 12:15 | Please post your timed queries in this forum. |
| 12:21 | This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching. |
| 12:29 | Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. More information on this mission is available at this link. |
| 12:41 | This is Meenal Ghoderao from IIT Bombay. Thank you for joining. |
