PhET-Simulations-for-Chemistry/C2/Diffusion/English

Title of the script: Diffusion

Author: Vidhi Thakur

Keywords: PhET simulation, Particles, Diffusion rate, radius of the particles, temperature, Graham’s law of diffusion, video tutorial.

Visual Cue	Narration
Slide Number 1 Title Slide	Welcome to this spoken tutorial on Diffusion.
Slide Number 2 Learning Objectives	In this tutorial, we will learn about, Factors affecting the rate of diffusion and Graham’s law of diffusion
Slide Number 3 System Requirement	Here I am using Windows 11 (64 bit). Google Chrome Version 103.0.50
Slide Number 4 Pre-requisites https://spoken-tutorial.org	To follow this tutorial, learner should be familiar with topics in high school science. Please use the link below to access the tutorials on PhET Simulations.
Slide Number 5 Link for PhET simulation point to https://phet.colorado.edu/en/simulations/diffusion/about	Please use the given link to download the PhET simulation.
Point to the file in the Downloads folder.	I have downloaded the Diffusion html file, to my Downloads folder.
Double click the file to open	To open the simulation double click on the file. File opens in your default browser.
Cursor on the interface.	This is the interface of Diffusion simulation.
Click on the PhET logo. Click on options and check projector mode and close the pop-up box.	Let us first switch the colour profile to projector mode. Click the PhET logo at the bottom right corner and select Options. In the Options pop-up box, check the Projector Mode and close the pop-up box. Now the simulation has a white profile for better visibility.
Cursor on simulation interface. Cursor on the divider.	The main panel opens with a rectangular screen. This represents the space in which the particles will diffuse. The green line at the centre divides the space into two halves. The two halves can be used to observe the process of diffusion.
Cursor on right panel. Point to Number of particles, Mass in AMU, Radius in pm and initial temperature in kelvin.	The panel on the right has various variables that can change the rate of diffusion. They are the Number of particles, Mass in AMU, Radius in picometres and initial temperature in kelvin. We will study the effect of these variables on diffusion rate later.
Cursor on spheres Cursor on arrows	Each variable has blue and red spheres shown as particles. Each variable has an up and down arrow button. This will help to increase or decrease the quantity of the variable.
Cursor on Analysis tools.	At the bottom, we can see the analysis tools. Center of Mass and Particle Flow Rate are used to check equilibrium. Scale and stopwatch are used for recording rate of diffusion.
Click the green plus button.	Let us click the green plus button at the top to expand the data section. It shows the total number of blue and red particles on each side of the divider. It gives the average temperature on each side of the divider.
Click and hold the up arrow till 50 particles	Let us add 50 blue particles to the space. Blue particles appear on the left side of the rectangle. The green Remove Divider button in the right panel is now active.
Check all analysis tools Cursor on blue box	Let us check all the analysis tools options. A blue box is seen at the top left. It shows the time in picoseconds, along with play and reset buttons.
Cursor on scale Cursor on blue bar	The scale at the bottom has 1 nm as the least count. The blue moving bar represents the centre of mass.
Click the Remove Divider divider button. Cursor on main panel	Let us now remove the divider by clicking on the Remove Divider button. Observe the movement of particles from one side to another. When particles move from higher concentration to lower concentration diffusion occurs.
Cursor on blue arrows. Cursor on blue bar.	The blue arrows represent the particle flow rate. A shift in the centre of mass is also seen as the blue bar moves. This happens because the system tries to maintain equilibrium.
Click on the Pause simulation button and Reset Divider button. Click on the play stopwatch button and remove divider Click on the play simulation button Click on the pause stopwatch button.	Let us see the effect of a number of particles on the rate of diffusion. Let’s first pause the simulation and reset the divider. Let's now start the stopwatch and remove the divider. Let’s play the simulation. Stop the timer when the number of particles on each side is equal. This is the equilibrium point and can be used to record the rate of diffusion.
Click on the Pause simulation button and Reset Divider button. Click on the up arrow button to increase the particles. Click on the play stopwatch button and remove divider Click on the play simulation button. Click Pause stopwatch button to stop the timer	Let us record the diffusion rate by increasing the number of particles. Let’s first pause the simulation and reset the divider. Let us increase the number of particles to 100, reset and start the stopwatch and remove the divider. Let’s play the simulation. Stop the timer when the number of particles on each side is equal. Let us continue this process. Let’s increase the number of particles by 50 each time till 200.
Slide Number 6 Table 1	Observe the values in the table. It shows the number of particles and time to reach equilibrium. As the number of particles increases, time to reach equilibrium decreases. Hence the rate of diffusion is directly related to the number of particles.
Click the Reset button to reset the simulation.	Let us reset the simulation to its default parameters.
Point to radius variable.	Let’s see the effect of radius on rate of diffusion.
Click and hold Number of particles up arrow till 100. Click and hold down the Radius arrow till 50 pm.	Let us increase the number of particles to 100 and decrease the radius to 50.
Check all the analysis tools options. Click on the green plus button.	Let us check all the analysis tools. Click the green plus button to show the data.
Click on the Pause simulation button. Click on the and play stopwatch button.	Click the Pause simulation button to pause the simulation. Let's play the stopwatch.
Click the Remove Divider button. Click the Play simulation button. Click the Pause stopwatch button. Point to the main panel.	Now remove the divider and play the simulation. Stop the timer when the number of particles on each side is equal. This is the equilibrium point and can be used to record the rate of diffusion.
Show the recording of the values.	Let us record the diffusion rate by increasing the radius. Let’s increase the radius by 50 each time and reach till 200 pico metre.
Slide Number 7 Table 2	This slide shows the radius of particles and time required to reach equilibrium. As the radius of the particles increases, time to reach equilibrium decreases. Hence the rate of diffusion is directly related to the radius of particles.
Click on the Pause simulation button and Reset divider button. Click on reset and play stopwatch button	Now let us see the effect of initial temperature(K) on the diffusion rate. Let us pause the simulation and reset the divider. Let's reset and play the stopwatch.
Click and hold down arrow of Initial Temperature (K) till 100 Kelvin. Click and hold up arrow of Radius till 125pm. Click on remove divider button Click on play simulation button Click on the Pause stopwatch button.	Let’s decrease the initial temperature to 100 Kelvin and increase the radius to 125 picometre. Now remove the divider and play the simulation. Stop the timer when the number of particles on each side is equal. This is the equilibrium point and can be used to record the rate of diffusion.
Show the recording of the values.	Let’s record the diffusion rate by increasing the initial temperature. Let’s increase the temperature by 100 Kelvin each time and reach till 400 Kelvin.
Slide Number 8 Table 3	Observe the values in the table. As the temperature increases, time to reach equilibrium decreases. Hence rate of diffusion and temperature are directly related.
Click on reset simulation button Click on the green plus button and check all analysis tools.	Now let us see the diffusion between two different particles. Reset the simulation to default parameters. Let us click the green plus button, and check the analysis tools.
Click and hold Up arrow of the number of particles of blue particles till 100. Click and hold Up arrow of the number of particles of red particles till 100. Click the Remove divider	Increase the number of both blue and red particles to 100. Remove the divider and observe the diffusion.
Cursor on particle flow rate arrow. Cursor on blue and red bar.	Particles move from higher concentration to lower concentration to attain equilibrium. This can be seen by particle flow rate arrows at the bottom. Observe that centre of mass also lies near the centre.
Click the Reset Divider button. Touch and hold down arrow on left side till 16 and right side till 4 Click on Remove divider. Click on Pause	Now let us see the relation between molar mass and diffusion. Let us reset the divider. I will change the mass of blue particles to 16 and red to 4. Remove the divider. I will pause and record the number of blue and red particles on both sides.
Slide Number 9 and 10 Rate of Diffusion of blue particles = 54 - 46 = 8 nm/ps Rate of Diffusion of red particles = 58 - 42 = 16 nm/ps Ratio of diffusion rate red particles/blue particles = 16/8 = 2 Molar mass blue particles = 16 Molar mass red particles= 4	The rate of diffusion of blue particles is 8 nanometer /picosecond The rate of diffusion of red particles is 16 nanometer /picosecond. The ratio of rate of diffusion is 2. The molar mass of blue particles is 16 and the molar of red particles is 4.
Slide Number 11 Graham’s Law of Diffusion Ratio of molar mass of blue particles/red particles = 16/4 = 4 Ratio of square root molar of mass blue particles/red particles = 2 Ratio diffusion rate red particles/blue particles <nowiki= ratio square root molar mass blue particles/red particles</nowiki Rate of diffusion is inversely proportional to the square root of its molar mass	Ratio of molar mass of blue particles and red particles is 4. Ratio of square root molar mass of blue particles and red particles is 2. From the calculations we have proved Graham’s law of diffusion. Rate of diffusion is inversely proportional to the square root of its molar mass.
Slide Number 12 Summary	With this we come to the end of this simulation. Let's summarise. In this tutorial we have learnt about, Factors affecting the rate of diffusion and Graham’s law of diffusion
Slide Number 13 Assignment	As an assignment, Verify Graham’s law of diffusion for particles of different molar masses.
Slide Number 14 About Spoken Tutorial Project	The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
Slide Number 15 Spoken tutorial workshops	We conduct workshops using spoken tutorials and give certificates. For more details, please contact us.
Slide number 16 Answers for THIS Spoken Tutorial 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 The spoken tutorial project will ensure an answer. You will have to register on this website to ask questions.	Please post your timed queries in this forum.
Slide number 17 Acknowledgment	The Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India
Slide Number 18 Thank you	This tutorial is contributed by Vidhi Thakur, a FOSSEE summer fellow 2022, and Madhuri Ganapathi from IIT Bombay. Thank you for joining.

Contributors and Content Editors

Madhurig, Snehalathak