Difference between revisions of "PhET-Simulations-for-Chemistry/C2/Diffusion/English"

Title Slide

Learning Objectives

• Factors affecting the rate of diffusion and

• Graham’s law of diffusion

System Requirement

Windows 11 (64 bit).

Google Chrome Version 103.0.50

Pre-requisites

https://spoken-tutorial.org

Please use the link below to access the tutorials on PhET Simulations.

Link for PhET simulation

point to

https://phet.colorado.edu/en/simulations/diffusion/about

File opens in your default browser.

Click on options and check projector mode and close the pop-up box.

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 the divider.

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.

Point to Number of particles,

Mass in AMU, Radius in pm and

initial temperature in kelvin.

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 arrows

Each variable has an up and down arrow button.

This will help to increase or decrease the quantity of the variable.

Center of Mass and Particle Flow Rate are used to check equilibrium.

Scale and stopwatch are used for recording rate of diffusion.

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.

Blue particles appear on the left side of the rectangle.

The green Remove Divider button in the right panel is now active.

Cursor on blue box

A blue box is seen at the top left.

It shows the time in picoseconds, along with play and reset buttons.

Cursor on blue bar

The blue moving bar represents the centre of mass.

Cursor on main panel

Observe the movement of particles from one side to another.

When particles move from higher concentration to lower concentration diffusion occurs.

Cursor on blue bar.

A shift in the centre of mass is also seen as the blue bar moves.

This happens because the system tries to maintain equilibrium.

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’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.

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’s first pause the simulation and reset the divider.

Let us increase the number of particles to 100.

Let's 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.

Table 1

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 and hold down the Radius arrow till 50 pm.

Click on the green plus button.

Click the green plus button to show the data.

Click on the and play stopwatch button.

Let's play the stopwatch.

Click the Play simulation button.

Click the Pause stopwatch button.

Point to the main panel.

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.

Let’s increase the radius by 50 each time and reach till 200 pico metre.

Table 2

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.

Reset divider button.

Click on reset and play stopwatch button

Let’s first pause the simulation and reset the divider.

Let's reset and play the stopwatch.

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.

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.

Let’s increase the temperature by 100 K each time and reach till 400 K.

Table 3

As the temperature increases, time to reach equilibrium decreases.

Hence rate of diffusion and temperature are directly related.

Click on the green plus button and check all analysis tools.

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 red particles till 100.

Click the Remove divider

Remove the divider and observe the diffusion.

Cursor on blue and red bar.

This can be seen by particle flow rate arrows at the bottom.

Observe that centre of mass also lies near the centre.

Touch and hold down arrow on left side till 16 and right side till 4

Click on Remove divider.

Click on Pause

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.

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 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.

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 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.

Summary

Let's summarise.

In this tutorial we have learnt about,

Factors affecting the rate of diffusion and Graham’s law of diffusion

Assignment

Verify Graham’s law of diffusion for particles of different molar masses.

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