Water Conference Proposal Li Bingjian, Bryan Neo 15S06F

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

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)

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)

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

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

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

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

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

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

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

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

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

Thank you!