Difference between revisions of "PhET-Simulations-for-Chemistry/C3/Sugar-and-Salt-solutions/English"

Title Slide

Learning Objectives

Change in concentration of the solution on:

• addition of a solute
• addition of a solvent
• evaporation

Learning Objectives

Identify whether the given compound is ionic or covalent.

System Requirement

Windows 11 (64 bit)

Java version 1.8.

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/sugar-and-salt-solutions

Move the cursor on the tabs, Macro, Micro and Water.

Macro, Micro and Water.

The main panel shows a container with inlet and outlet water faucets.

Outlet water faucet is placed at the bottom-right of the container.

The markings show 0 Litre, 1 Litre and 2 Litres.

Shake the salt dispenser to add salt to the container.

Point to the options.

From here we can select the solute type.

Let us keep the default solute as salt.

Click on the show values checkbox

Let us check the Show values checkbox to see the concentration values.

Drag the Evaporation slider from none to lots.

To evaporate water, drag the slider from none to lots.

Observe the change in the concentration in the Concentration panel.

As water evaporates the concentration of the salt increases.

On clicking this button salt is removed from the solution.

Click on the show value check box.

Let the water level in the container be at 1 litre mark.

Let us check the Show values box.

Definition of concentration

Molarity is one way of expressing concentration.

Molarity = Number of moles of the solute by Volume of solution in litres(L)

Molarity (M) = n/V

Shake the dispenser to add salt

I will record the change in concentration.

Let's tabulate the values to calculate the amount of solute.

Table 1

Observe the concentration in the panel.

As per the formula concentration is inversely related to the volume of solution.

Hence on increasing the volume, concentration decreases.

Slide the evaporation slider to the right.

Cursor to the concentration panel.

I will drag the evaporation slider from none to lots to decrease the volume.

We can see an increase in concentration as the volume decreases.

Cursor to red electrode

Cursor to bulb and battery

It consists of a circuit with a green negatively charged anode.

The red positively charged electrode acts as a cathode.

A bulb is connected to a battery to observe the conductivity.

Drag the circuit inside the solution

Cursor towards the bulb.

Let us drag the circuit inside the solution.

The bulb glows now.

Cursor to the bulb

The bulb glows brighter as the concentration of salt in the solution increases.

Hence intensity of brightness increases.

Click on the show values checkbox

Let us select the Show values checkbox in the right panel.

Click on the Sugar radio button to select sugar as solute.

Shake the dispenser to add salt

Let's add more sugar to the container and record the concentration.

Let's tabulate the results.

Table 2

Here I have calculated the amount of sugar for different concentrations.

Drag the circuit inside the solution

Cursor towards the blub

Let us drag and place the circuit inside the solution.

This time the bulb does not glow.

Hence cannot conduct electricity.

The Solute panel shows different solutes.

Concentration panel, represents sodium as purple spheres and chloride as green spheres.

Sucrose is represented as a molecule with white, grey and red spheres.

Cursor on pause and slow button

On the bottom left pause and slow-motion buttons can be seen.

Slow-motion button can be used to observe the dissociation in slow motion.

Click on the pause button.

Click the slow-motion button multiple times.

Cursor in right panel

Click the pause button as soon as the molecules touch the surface of water.

Now click the slow-motion button multiple times to observe slow dissociation.

I will continue to click the button until all the atoms ionize.

On adding salt to water it dissociates into ions of opposite charges.

Also, observe an increase in concentration of sodium and chloride ions in the right panel.

Click on the Sucrose option in the solute panel.

Add Sucrose to the container.

Cursor towards the container.

Now I will change the solute to Sucrose.

Let's add Sucrose to the container.

As observed, Sucrose does not dissociate into ions.

So it will not show conductivity as shown by salts.

You can practise with the other solutes present in the panel.

Click on the button.

Close the periodic table box.

This gives information about the elements present in the selected molecule.

They can be individually identified as metals or non-metals.

Close the periodic table box.

Cursor on magnified view.

It shows a magnified version of molecular interactions between water molecules.

Cursor on options and buttons.

Point to sugar highlight option.

Point to the sugar molecules in the Sugar bucket.

Uncheck the Sugar highlight option.

Point to the sugar molecules in the Sugar bucket.

Click the Water partial charges option.

Cursor on water partial charges in the container.

It has two options, Water partial charges and Sugar highlight.

Sugar highlight option is selected by default.

Here the sugar molecules are highlighted in yellow colour.

Let's uncheck the Sugar highlight option.

Observe that sugar molecules appear in their default colours.

Click the Water partial charges option to see the partial charges on the water molecule.

Click on the Sugar in 3D button.

Point to the model in the window.

Click on the Ball and stick model.

Now I will click the Sugar in 3D button.

A window opens with a 3D model of sugar in space fill format.

Now Let's select the Ball and stick option.

The sticks in the model represent covalent bonds between adjacent atoms.

Cursor on the magnified view.

Cursor on negatively charged charges.

Cursor on positively charged charges.

Observe the orientation of water's partial charges with sodium and chloride ions.

Negative partial charges coloured red are aligned around sodium ions.

Positive charges coloured white are aligned around chloride ions.

This demonstrates the dissociation at molecular level in the water.

Click on the water partial charges option.

Select the water partial charges option in the Show panel.

Cursor on magnified view.

This time the molecules are not aligned nor do they dissociate.

This is because sugar is a complex molecule with covalent bonds.

This resists its dissociation in water, so no ions are formed.

Summary

Let's summarise.

In this tutorial we have learnt about,

Change in concentration of the solution on:

• addition of a solute
• addition of a solvent
• evaporation

Conductivity of a solution.

Identify whether the given compound is ionic or covalent.

Assignment

Explore more solutes and observe their dissociation in water.

Interpret the possible dissociated ions and predict their conductivity.

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Acknowledgement

• summer fellow 2022, IIT Bombay
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