Which best describes why a chemical change is different than a physical change?

a. a chemical change results in a different state of matter, and a physical change results in a new substance being formed.

b. a chemical change is used to identify characteristics of a substance, and a physical change identifies the behavior of a substance when in a reaction.

c. a chemical change results in a new substance being formed, whereas a physical change will result in a different state of matter.

d. a chemical change is used by scientists to create new substances, and a physical change happens naturally.

To understand the electric potential and electric field of a point charge in three dimensions consider a positive point charge q, located at the origin of three-dimensional space. throughout this problem, use k in place of 14? ? 0. part adue to symmetry, the electric field of a point charge at the origin must point from the origin. answer in one word. part bfind e(r), the magnitude of the electric field at distance r from the point charge q. express your answer in terms of r, k, and q. part cfind v(r), the electric potential at distance rfrom the point charge q. express your answer in terms of r, k, and q part dwhich of the following is the correct relationship between the magnitude of a radial electric field and its associated electric potential ? more than one answer may be correct for the particular case of a point charge at the origin, but you should choose the correct general relationship. a)e(r)=dv(r)drb)e(r)=v(r)rc)e(r)=? dv(r)drd)e(r)=? v(r)r