Which of the following reactions best illustrates the Law of Conservation of Mass? A. H2O2 → H2O + O2
B. Na + CuS → Na2S + 2 Cu
C. K + AgCl → KCl + Ag
D. NaOH + 2 HCl → NaCl + H2O

In a voltaic cell, electrons flow from the (positive/negative) to the (positive/negative) terminal.

Waves are used in many practical applications to support work, entertainment, and health. one example is the use of ultrasound imaging to safely track the development of a growing fetus. what is a specific example of a practical application of waves in medicine, entertainment, safety, or other fields? provide a brief explanation of how the properties of waves are useful to that application.

Scientists follow specific processes in order to determine valid explanations and conclusions from observations. david observed strange lights in the sky above his home outside of roswell, new mexico. the only explanation that makes sense to him is that there are ufos in the area. what should david do next to verify his explanation?