Plop, Plop, Fizz, Fizz

Measure how water temperature changes the rate of a chemical reaction. Heat the water, drop the Alka-Seltzer tablet, and time the fizz until the tablet is completely gone.
Reaction Rate Lab

Set Up The Water

22 °C
0° ice22° room50°95° near boiling
The hot plate (or ice bath) will bring the water to your target, then hold it there.

Run The Trial

Simulation speed
Cold-water trials take several real minutes. Speed up time — the stopwatch still reports the true reaction time in seconds.
Fizz sound
Controlled variables
Same 400 mL beaker · 250 mL of water · 1 whole tablet, same brand and size · tablet dropped, not stirred

Lab Bench

Heater off
Waiting
Water: 22.0 °C
Tablet left: 100%
Trials recorded: 0

Instruments

0:00.0
Reaction stopwatch
Starts the instant the tablet hits the water. Stops when the tablet is completely dissolved.
IR Thermometer
22.0 °C
71.6 °F
Fizz loudness
Sound level0 dB
More collisions per second → more CO2 bubbles bursting per second → a louder fizz.
Last time—
Last temp—
Peak loudness—

Data Table

#Water temp (°C)CategoryTime to dissolve (s)Peak loudness (dB)
Room temp avg (18–26°C)
—
Hot water avg (≥45°C)
—
Cold water avg (≤10°C)
—

Graph — Reaction Time vs. Water Temperature

Each dot is one recorded trial. Notice the curve is steep on the cold end — a 10 °C change matters far more in cold water than in hot water.

Bonus Content — Testing pH With Indicator Strips

pH measures how acidic or basic (alkaline) a water-based liquid is, on a scale from 0 to 14. It tells us how many hydrogen ions are present: 0–6 are acids, 7 is neutral, and 8–14 are bases.
strong acidweak acidneutralweak alkalistrong alkali
Item
Your estimated pH
Actual pH
Strip color
Test
Type your prediction first, then dip the strip — that is what the “Est. pH” row on your lab sheet is for.

How To Use This Simulation

  1. Drag the temperature slider (or tap a preset) to pick the water temperature you want to test, then press Set Water Bath. Watch the IR thermometer until the water reaches your target and holds steady.
  2. Press Drop Tablet. The stopwatch starts the moment the tablet hits the water, and the fizz-loudness meter shows how violently the reaction is going.
  3. If the trial is slow (cold water), switch the simulation speed to 5× or 20×. The stopwatch still reports the real reaction time in seconds.
  4. When the tablet is completely gone, the stopwatch stops. Press Record Trial to send that temperature and time to the data table.
  5. Press New Beaker for fresh water, change the temperature, and run it again. Do at least one room temperature trial and one hot water trial so you can fill in your lab sheet.
  6. Read the graph to see the pattern, and use the three average boxes under the data table for your class-average row.
  7. For the bonus, type your estimated pH in each box, then dip the strips: plain water first, then the fizzing mixture, then the mixture after it has stood for five minutes.

The Science Behind The Model

The tablet holds solid citric acid and sodium bicarbonate. They cannot react while dry — the water dissolves them so the particles can finally collide:

3 NaHCO3 + C6H8O7 → 3 CO2 ↑ + 3 H2O + Na3C6H5O7

That escaping carbon dioxide gas is the fizz. Hotter water gives the particles more kinetic energy, so they collide more often and harder — more of those collisions have enough energy to react, so the tablet disappears sooner.

This sim uses a Q10 = 1.75 rate model, meaning the reaction runs about 1.75× faster for every 10 °C you add:

t = 3 + 57 · 1.75(20 − T)/10 seconds

The constant 3 s is a floor — even in near-boiling water the tablet still needs time to physically break apart and mix. Each trial also gets a small random wobble (±4%), just like real groups in a real lab, so your data will not sit perfectly on the curve.

Physical or chemical change? Watch for the evidence: a new substance (CO2 gas) is produced, bubbles form, and the change cannot be reversed by re-freezing or evaporating the water.