54 Heating Curve 140 120 100 80 Temperature c 60 H F 40 C D 20 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Time (min) Using the heating curve shown above: a) Describe what is occurring in each of the labeled sections. b) Identify when heat is added. c) What is the melting point of the solid? d) What is the freezing point of the liquid? e) At what temperature does the liquid boil? 55. What are isotopes of atoms with unstable nuclei called? a) radioactivity b) radioisotopes c) radioactive decay d) radiation 56. What happens to the mass of an atom when it undergoes alpha decay? a) The mass decreases by 4. b) The mass decreases by 1. c) The mass increases by 4. d) There is no change in mass. 57. What is the name of the process in which a large radioactive isotope is broken into smaller isotopes? a) beta emission b) nuclear fission c) transmutation d) nuclear fusion 58. The mass number is the sum of... Not a) the electrons and protons b) protons and neutrons c) neutrons and electrons