When a solid melts at its melting point to become a liquid at the same temperature, its internal energy increases. What is the primary cause of this increase?
an increase in the average kinetic energy of the particles
an increase in the potential energy of the particles as they break free from their fixed positions
a decrease in the average speed of the particles
a decrease in the average separation of the particles
313 exam-style questions on CIE IGCSE Physics 2.2.3a Melting, boiling, condensation and solidification. Each one has a worked solution and a mark scheme showing where the marks go.