1. Water Conference Proposal
Li Bingjian, Bryan Neo 15S06F

2. Idea Making carbonated water
Carbonated water is the main ingredient of soft drinks and sparkling water
Investigate a simple and direct method of making dry ice

3. Principles behind H2O(l) + CO2 (aq) ⇄ H2CO3 (aq)
Carbon Dioxide will dissolve into aqueous form first, before reacting with water to form carbonic acid
However, reaction is reversible, hence it reaches dynamic equilibrium at some point
H2O(l) + CO2 (aq) ⇄ H2CO3 (aq)

4. Principles behind (con’t)
Since carbonic acid (H2CO3) is a weak acid, it dissociates in the following two steps
H2CO3 (aq) + H2O (l) ⇄ HCO3- (aq) + H3O+(aq)
HCO3- (aq) + H2O (l) ⇄ CO32- (aq) + H3O+(aq)

5. Principles behind (con’t)
Use Henry’s Law to estimate solubility of CO2 in water
At constant temp, amt. of given gas that dissolves in a given type and vol. of liquid is directly proportional to partial pressure of that gas in equilibrium with that liquid
c: concentration of a gas at a fixed temp. in a particular solvent
k: Henry's law constant (varies for different gases and solvents )
Pgas: Partial pressure of gas
Pgas=kc

6. The activity Experimental Theoretical
Hands-on activity making carbonated water
Design of system to maximize efficiency
Theoretical
Learning the relevant concepts of equilibria
Qualitative and quantitative investigation

7. Experiment 1
Find out mass of sample of dry ice by taring the mass of a cup before placing dry ice into cup and weighing again
Drop the sample of dry ice in water
Calculate the amount of carbon dioxide that dissolves
Participants can try to modify the set-up to allow as much carbon dioxide to dissolve into the water as possible

8. Experiment 2 Using a pH probe, measure the pH of the carbonated water
Divide the carbonated water into 10 separate small beakers.
For each beaker, heat on a hotplate to a fixed temperature and allow system to reach equilibrium.
Measure the pH and mass of the carbonated water in each of the beaker

9. Mini competition
Challenge the participants to make the most carbonated water
OR/AND
Challenge the participants to make the most carbonated water given a fixed amount of dry ice
Prizes can be given out to the winners

10. Limitations
Method of weighing dry ice yields rather inaccurate results since it constantly undergoes sublimation
Participants have to weigh the dry ice fast

11. Data Analysis and Theory work
Participants to elucidate general trends from the data collected
Guided theoretical problems allow participants to calculate the predicted values
Compare prediction to actual experimental data

12. Link to carbon dioxide in blood
Homeostatic mechanisms controlling our breathing rate depends on the concentration of carbon dioxide in our blood
The exact same equilibrium is established, and the concentration of bicarbonate ions is detected by our body

13. Materials required General lab glassware (beakers, stirring tubes)
Hotplates
Electronic mass balance
Dry ice (and necessary insulated containers)
Gloves/Spoons (for handling dry ice)
1.5L bottles
Plastic tubes
Balloons
Generally low budget

14. Thank you!