Step 2: Chemical Reaction
Put some baking soda in one of the containers. I used a heaping spoonful in a measuring cup.
Add vinegar very slowly. Too much and the container will overflow with foam. Add a little, wait for the foaming to subside, add a little more.
Keep adding vinegar a little at a time, stirring the mixture.
Stop adding vinegar once the mixture stops bubbling, even with stirring.
What you should have now is a solution of sodium acetate in water. I ended up with the measuring cup nearly full of solution.