21.2 Heat (page 409) 16. Define heat. 17. Describe the spontaneous energy transfer that occurs when you touch a cube of ice. 18. Is the following sentence true or false? A cup of hot water contains more heat than a cup of cold water. 19. Explain the meanings of the terms thermal energy and internal energy. 20. Define thermal contact. 21. When two substances of different temperature are in thermal contact, heat flows from the - substance into the -substance. 22. Is the following sentence true or false? Heat always flows from a substance with more total molecular kinetic energy to a substance with less. 23. Is the following sentence true or false? Heat never flows on its own from a cooler substance into a hotter substance.. 21.3 Thermal Equilibrium (page 410) 24. After objects in thermal contact with each other reach the same temperature, the objects are in _ 25. When a thermometer is in contact with a substance, heat flows between them until 26. Why is it important for a thermometer to be small in comparison to the substance it is measuring