SCH4U - Chemistry 12 (2024-25) - A
SCH4U-25A
**Strong vs. Weak Acids & Bases Musical Chairs Group Activity 4-3
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Strong vs. Weak Acids & Bases – Musical Chairs Group Activity Demo
Click here to download instructions for this activity
Teacher instructions: this activity is meant to review some of the concepts of acids and bases and demonstrate the differences in behaviour between strong and weak acids/bases. This activity is fun and serves as a good visual aid for students to see differences in how quickly strong acids dissociate compared to weak acids. The key to this activity working is that when doing the musical chairs for strong acids/bases, the interactions are very short (3-5 seconds, “hello, how are you”) whereas for weak acids/bases the interactions are much longer (10-15 seconds). The results should be that when the music stops, very few pairs are sitting for the strong acids/bases vs. the weak acids bases.
Before the demonstration, you should do a brief review of the differences between strong and weak by using a T-chart to compare and contrast with the headings: Strong acid | Weak Acid and a second T-chart with the headings Strong Base | Weak Base. (items to compare and contrast include: examples of each, behaviour in water, generic formulas, commercial uses/examples, etc.)
For example:
|
Strong Acids |
Weak Acids |
|
HCl, HBR, HI, H2SO4 etc... |
CH3COOH, H2C2O4 etc... |
|
Complete dissociation in water |
Incomplete dissociation in water |
|
HA → H+ + A- |
HA ↔ H+ + A- |
You will then demonstrate how strong and weak acids behave by playing musical chairs using the instructions below. You should play 4 rounds (strong acid, weak acid, strong base, weak base) and record the results of the number of sitting vs. standing students after each round.
Musical Chairs Instructions
|
|
Step 1: Before Dissociation |
Step 2: Equilibration |
Step 3: After Dissociation |
Debrief |
|
Strong Acid |
- students given piece of paper - students find partner - one writes H+ on paper while other writes Cl- - students hold paper in front of chest |
- students mingle around the room when music plays - students must sit down and hold brief conversation (~1-2sec just saying hello) when they encounter another student with the opposite symbol (H+ matches with Cl-) -pairs then stand up and start mingling again |
- students freeze when music stops (~60 seconds of music) - # of students standing up versus sitting down is recorded |
- majority of students should be standing up
- strong acid should be completely dissociated (or close to it)
HCl → H+ + Cl- |
|
Weak Acid |
- students given piece of paper - students find partner - one writes H+ on paper while other writes A- - students hold paper in front of chest |
- same as strong acid except conversation must be ~10-15sec (example conversation has pairs asking each other their favourite food, music, etc.) |
- students freeze when music stops (~60 seconds of music) - # of students standing up versus sitting down is recorded |
- majority of students should be sitting down - weak acid should be incompletely dissociated
HA ↔ H+ + A- |
|
Strong Base |
- students given piece of paper - students find partner - one writes Na+ on paper while other writes OH- - students hold paper in front of chest |
- students mingle around the room when music plays - students must sit down and hold brief conversation (~1-2sec just saying hello) when they encounter another student with the opposite symbol (Na+ matches with OH-) -pairs then stand up and start mingling again |
- students freeze when music stops (~60 seconds of music) - # of students standing up versus sitting down is recorded |
- majority of students should be standing up - strong base should be completely dissociated
NaOH → Na+ + OH- |
|
Weak Base |
- students given piece of paper - most students are NH3 - remaining students find partner - one writes H+ on paper while other writes OH- |
- same as weak acid except NH3 matches up with H+ while OH- matches with nobody |
- students freeze when music stops (~60 seconds of music) - # of students standing up versus sitting down is recorded |
- a few students should be sitting down as NH4+ - weak base incompletely dissociates to form NH4+
NH3 + H2O ↔ NH4+ + OH- |