Water Conference Proposal

Li Bingjian, Bryan Neo 15S06F

IdeaMaking 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 behindCarbon 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)

Since carbonic acid (H2CO3) is a weak acid, it dissociates in the following two steps

Principles behind (con’t)H2CO3 (aq) + H2O (l) ⇄ HCO3

- (aq) +

H3O+(aq)HCO3

- (aq) + H2O (l) ⇄ CO3

2- (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 activityExperimental

Hands-on activity making carbonated waterDesign of system to maximize efficiency

TheoreticalLearning the relevant concepts of equilibriaQualitative and quantitative investigation

Experiment 1Find 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 2Using a pH probe, measure the pH of the

carbonated waterDivide 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 competitionChallenge the participants to make the most

carbonated waterOR/ANDChallenge the participants to make the most

carbonated water given a fixed amount of dry ice

Prizes can be given out to the winners

LimitationsMethod 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 workParticipants 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 bloodHomeostatic 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 requiredGeneral lab glassware (beakers, stirring

tubes)HotplatesElectronic mass balanceDry ice (and necessary insulated containers)Gloves/Spoons (for handling dry ice)1.5L bottlesPlastic tubesBalloons

Generally low budget

Thank you!