12. what is a phase change? construct a heating-cooling curve for a substance that freezes at –23.0 °c and has a boiling point of 67.0 °c. name all possible changes that can occur among the vapor, liquid, and solid phases of this substance, and name the four phase change enthalpies involved. indicate whether these changes are exothermic or endothermic. (6 points)

What are atoms of the same element with varying number of neutrons

Awoman holds a book by placing it between her hands such that she presses at right angles to the front and back covers. the book has a mass of m = 1.8 kg and the coefficient of static friction between her hand and the book is μs = 0.67. no attempt 50% part (a) what is the weight of the book, fgb in newtons?

Athin nonconducting rod with a uniform distribution of positive charge q is bent into a circle of radius r. the central perpendicular axis through the ring is a z-axis, with the origin at the center of the ring. a) what is the magnitude of the electric field due to the rod at z = 0? n/c (b) what is the magnitude of the electric field due to the rod at z = infinity? n/c (c) in terms of r, at what positive value of z is that magnitude maximum? r (d) if r = 4.00 cm and q = 9.00 µc, what is the maximum magnitude? n/c