(2) water pollutants in the nitrogen and phosphorus content is too high, here "nitrogen and phosphorus" refers to the elements;
(3) the tap water is not pure water, if you want to make pure water, should be taken to purify the method is distillation; Detergent has an emulsifying function, can wash the oil on the dishes;
(4) by the figure 1 can be seen, the solution of substance A can no longer dissolve substance A, so it is a saturated solution, shown in figure 2, 20 ℃, solubility curve b is located below the solubility curve a, indicating that at this time, a is greater than the solubility b; figure 1 shows that the substance B is dissolved all the time and the substance A has a solid material remaining, indicating that at this time, B The solubility of the substance is greater than the substance a; Therefore, Figure 2, a indicates that the solubility curve of the substance a; the solubility of the substance a with the increase in temperature and increase, in order to make the remaining a solid in the test tube to continue to dissolve the method can be used is to increase the temperature, will be 10 ℃ when the a saturated solution is warmed to 20 ℃ (solvent does not evaporate), a solubility with the increase in temperature and increase the solubility of the bottom of the undissolved a dissolved to make the solute The mass of the solution increases, so the mass fraction of solute becomes larger.
The answer is: (1) H2O2; (2) A; (3) distillation, emulsification; (4) A, a, increase the temperature, become larger.