NCSU – Dept. of Chemistry – Lecture Demonstrations
Equilibrium
Equilibrium With Water
Description: The concept of dynamic equilibrium is demonstrated by adding and
removing water from two beakers.
Materials:
Water
Food coloring
2 4-L beakers
2 400 mL beakers
Procedure:
1. Fill one of the 4-L beakers with 2-3 L of water. Add a few drops of food
coloring for a better visual. This beaker will play the role of “reactants”.
The other beaker will remain empty and will hold the “products”.
2. Using two volunteers, assign one to a “reactants” beaker and the other to
a “products” beaker. Have the volunteers simultaneously scoop a beaker
full of material from their respective 4-L beaker and add those contents to
the other 4-L beaker. The “reactants” student will add 400 mL to the
“products” 4-L beaker and the “products” student will add 0 mL to the
“reactants” 4-L beaker. Repeat until equilibrium is reached.
3. Alternatively, to represent a faster rate of forward reaction, the “reactants”
student can use a larger beaker than the “products” student.
Discussion: This demonstration is helpful to illustrate the concept that
equilibrium occurs when the rates of the forward and reverse reactions are the
same, not when the reaction has stopped.
References:
Briggs, M. W. “Teaching Chemical Equilibrium Using a Macro Level Analogy.”
2006 Biennial Conference on Chemical Education.
Video:
http://www.youtube.com/watch?v=CMs2WhGY3NE