Explain the challenges in developing an accurate rating system for earthquakes. What kinds of variables are there?

If the atomic mass of an atom is 34 and the atom contains 13 protons, how many neutrons does the atom contain?

Identify the electromagnets with poles that are reversed from the electromagnet shown above

How can a give a full method for the experiment of separating sand from water by filtration? 1-materials 2-steps 3-conclusion also for water and salt separated by the evaporation or distillation process