You need to determine what you think will melt the fastest, and that will be your hypothesis. If you think that pepper will melt it faster, you would say "My hypothesis is that the pepper will melt ice faster than the other variables (sand, salt, and sugar)."
Ice melts at a standard rate proportional to itself, so if all ice pops are the same size they will melt at the same rate. However if some brands have wider ice pops than others, they will melt slower.
Out of all possible chemicals that might be used to melt ice, chances are fuming sulfuric acid would melt it the fastest, although you would not actually want to use it on your driveway, since you would be sacrificing safety for speed.
i think all the liquids will melt at the same speed but it depends on the viscosity of the liquid. If salt water is one of your liquids I think salt water will melt the fastest because salt melts ice. From C00kie_cream
it will depend on which of these waters is hotter. the hotter the water the faster the ice will melt. doesn't matter if the water is fresh or salty. its the temperature of the water that will determine how fast the ice melts.
The highest temperature you can provide! To melt, the ice requires a heat source to provide the latent heat of fusion needed to accomplish the phase change from solid to liquid. The faster you can provide this heat (i.e., the higher the temperature), the faster it will melt.