Materials chalk calcium hydroxide filter paper phenolphthalein heat source two pyrex beakers directions crush some classroom chalk (a mixture of limestone and gypsum) finely. mix chalk into water in a beaker. pour the mixture through filter paper. the water appears to be "pure." boil the water or let it evaporate away. what is left? water also dissolves and transports minerals. in a beaker, mix calcium hydroxide and water. filter until clear. fill another container with water. obtain some phenolphthalein solution and add a few drops to a glass of "pure" water. add a few drops to the water mixed with calcium hydroxide. give the results explain the results.