August 27, 2013
Introduce your students to core chemistry concepts as well as data collection and analysis with a quick demonstration using common household chemicals. This classic demonstration of a chemical reaction is quantified and enhanced with pH, temperature and conductivity measurements using the Advanced Chemistry Sensor. This quick demonstration will help the students think about some of the concepts that they will see throughout the year and the types of measurements that they can make to explore those concepts.
pH vs. Time
Overall, the pH increases as the reaction occurs. After the first tablet was added the pH increased, then leveled off. At around 100s, another tablet was also added causing the pH to increase again. Gas formation is also noticeable in the beaker.
Since the Temperature and Conductivity Probes were also in the solution, there are more opportunities for measurement-based explorations of the system.
pH and Temperature vs. Time
Most students will be surprised to find the temperature decreases during this endothermic reaction. As each tablet is added, the temperature decreases while the pH increases.
pH, temperature and conductivity vs. Time
The conductivity relationship is more complicated because it will be affected by the weakness of the acid, the formation of ions in the reaction and the formation of a gas.
The reaction of antacid and vinegar provides a nice visual indication that a chemical change is talking place. By monitoring the reaction with probeware, core chemistry concepts (acids and bases, electrolytes, and thermochemistry) can be also introduced.
Time permitting, have the students perform other experiments with beakers of "unknowns" to see of visual observations match probeware data.
There will be a color change to green, but the measurement data will not indicate a chemical change
There will be no obvious visual indication of a chemical reaction, but the measurements will indicate that a change has taken place.