Visualizing Mixing with Sugar and Salt Solutions PhET simulation

Learning Objectives: Describe the process of solution formation for salts versus molecular covalent compounds. Identify the differences in an ionic solution (with or without polyatomic ions) and a molecular

solution.

Directions: Open the Sugar and Salt Solutions simulation at http://phet.colorado.edu

1. Move the conductivity tester to the solution.2. Shake some salt into the water.

a. Does the conductivity tester light up?

b. What kind of compound causes the conductivity tester to light?

3. Click on the “remove salt” button.4. Change the solute to sugar and shake some into the water.5. Test the solution again with the conductivity tester.

a. Did it light up?

b. What type of compound is this?

6. Click on the “Micro” tab at the top of the page.7. Select the sodium chloride solute.8. Shake some salt into the water. What happens to the salt as it mixes with the water?

9. Look at the Concentration graphic. a. How do the concentrations of the 2 ions compare?

b. How would the concentrations of the cation and anion compare if the salt had been CaCl2? Explain your prediction.

STOP – Come to a consensus on 9b with another partner pair before moving on. Initials: _________10. Now move the evaporation slider to the right and hold until all the water has evaporated.

Adapted from an activity developed by D. Kloster | Silver Creek High School 1

a. What do you observe?

b. Is the substance, NaCl, different than when it was first added to the water?

11. Add water and move the evaporation slider again, this time take notice of the ion concentrations as you do so. What happens to the ion concentrations as the water evaporates?

12. Click the reset button at the bottom.13. Select the solute glucose.14. Add the sugar to the water

a. What do you observe?

b. How does process of solvation (dissolving) for sugar differ from that of salt?

c. Which solution results in a greater number of particles in solution- salt or sugar (assume you start with 2 molecules of each)?

15. Use the slider at the bottom to evaporate the water. a) What did you observe? How is the formation of sugar crystals different from the formation

of salt crystals?

16. Now, click on the “Water” tab at the top. a. What do the RED spheres represent?

b. What do the WHITE spheres represent?

c. Does it have polar bonds? How do you know?

d. Is the molecule polar or nonpolar? How do you know?

Adapted from an activity developed by D. Kloster | Silver Creek High School 2

17. Click and drag a sodium chloride crystal into the water. Immediately click the “pause” button in the lower left.

Notice that the water molecules surround the ions as it dissolves. This process is called hydration.

a. Which end of the water molecules seems to face the Na+ ion- the red end or the white end?

b. Is this end more positive or more negative?

c. Which end of the water molecules seems to face the Cl- ion?

d. Is this end more positive or more negative?

e. Draw the hydration of 1 formula unit of NaCl. Watch for CHARGES and ORIENTATION of water molecules.

18. Click the reset button.19. Repeat the process for glucose.

a. Does the sugar molecule break up?

b. Do the water molecules orient themselves in any particular way? Why do you think this is?

Adapted from an activity developed by D. Kloster | Silver Creek High School 3

20. BIG IMPORTANT KEY QUESTION:a) Ionic compounds, like NaCl or CaCl2, (Circle 1: do/do not) dissociate into ions.b) Covalent compounds, like sugar, (Circle 1: do/do not) dissociate into ions.

21. Explain why ionic compounds, like KCl or CuCl, are able to dissolve in water, while other ionic compounds, like AgCl, can’t dissolve in water (or would form a precipitate in a reaction). Your explanation should include a description of relative strengths of interactions between particles (“The attractions between ____ and _____ is stronger than the attractions between ____ and ____, so the compound remains a solid and does not dissolve.”)

STOP – Come to a consensus on 20-21 with another partner pair before moving on. Initials: _________

22. Fill in the box below for the solvation of potassium nitride.

Formula: Potassium nitride – K3NBefore Dissolving (1 formula unit of ionic compound)

After Dissolving (4 water molecules oriented around each ion)

Balanced Equation:

K3N(s) 3K+1(aq) + N-3(aq)

Adapted from an activity developed by D. Kloster | Silver Creek High School 4

23. Why do you think the three separate potassium ions do NOT stick together when they are dissolved in water? (Hint – what might happen as two K+ ions get close to one another?)

STOP – Come to a consensus on 22-23 with another partner pair before moving on. Initials: _________

24. Polyatomic ions are held together by covalent bonds. Based on your previous data, choose the best representation of the hydration of AlPO4.

Option #1: AlPO4 Al+3 + P-3 + 4O-2

Option #2: AlPO4 Al+3 + PO4-3

Explanation:

Adapted from an activity developed by D. Kloster | Silver Creek High School 5

24.Formula: Sodium Chloride – AlPO4

Before Dissolving (1 formula unit of ionic compound)

After Dissolving (4 water molecules oriented around each ion)

Balanced Equation:AlPO4 (s) Al+3(aq) + PO4

-3(aq)

24.

25.

STOP – Check in with SCHLOEMER before moving on. Initials: _________

Adapted from an activity developed by D. Kloster | Silver Creek High School 6

Exercises – complete in your composition notebook: 1. Write the formulas for the following ionic compounds.

a. Copper (II) sulfideb. Iron (III) chloridec. Aluminum oxided. Calcium chloridee. Potassium nitratef. Calcium phosphateg. Copper (II) carbonateh. Aluminum phosphatei. Iron (III) sulfate

Simulate two formula units of each compound in the space below. Make sure to:2. Identify the smallest particles that can be separated.3. Sketch how each separated ion would interact with 4 water molecules each. Make sure you can

explain why the waters are oriented this way.4. Finally, write an expression for this process with the correct notation for the chemical species.

Make sure your expression is balanced.

Example: Formula: Sodium Chloride - NaClBefore Dissolving (TWO formula units of ionic compound)

After Dissolving (4 water molecules oriented around each ion)

Balanced Equation:NaCl(s) Na+1(aq) + Cl-1(aq)

Adapted from an activity developed by D. Kloster | Silver Creek High School 7

Mastery Check – Ionic vs. Covalent Compounds Dissolving in Water1.

2. When the compound Mg(NO3)2 dissolves in water, what species do you expect to exist in solution? How many of each will there be for every Mg(NO3)2 unit dissolved?

3. What did the student forget in each drawing? Describe or draw how you’d fix it. (Note: It has NOTHING to do with the number of water molecules present).

Adapted from an activity developed by D. Kloster | Silver Creek High School 8

4. What did the student forget in each drawing? Describe or draw how you’d fix it. (Note: It has NOTHING to do with the number of water molecules present).

Adapted from an activity developed by D. Kloster | Silver Creek High School 9