Answer:
people walking on the sidewalk crush the calcium chloride pellets.
Step-by-step explanation:
When calcium chloride pellets are crushed with feet it increases the surface area of the calcium chloride. As the surface area increase the number of collision between the reactant molecules increases. Here the reactant molecules are calcium chloride ions and water molecules. In the process of dissolution the calcium chloride ions get hydrated by the dipoles of the water molecules. As the frequency of collision increases it lowers the activation energy or threshold barriers to start a reaction.