A thermal system has internal energy, associated with the microscopic motion and interactions of its atoms and molecules. Temperature is related to the average kinetic energy of those particles: a higher temperature generally corresponds to greater average kinetic energy.
When objects at different temperatures are brought into contact, energy spontaneously transfers from the hotter object to the colder one. This transfer continues until they reach the same temperature, a condition called thermal equilibrium. The transfer occurs because of the temperature difference, not because one object is doing mechanical work on the other.
All flashcards
What is heat?
Heat is the spontaneous transfer of energy caused by a temperature difference, typically from a hotter system to a colder one.
How do heat and temperature differ?
Temperature describes the thermal condition of a system and relates to the average kinetic energy of its particles. Heat is energy being transferred because of a temperature difference.
What is thermal equilibrium?
Thermal equilibrium is the condition in which systems in thermal contact have reached the same temperature, so there is no net heat transfer between them.
What is the relationship between a food Calorie and a kilocalorie?
A food Calorie, written with a capital C, is one kilocalorie: 1 Cal = 1 kcal = 1000 cal.
What did Joule’s mechanical equivalent of heat demonstrate?
It showed that work and heat transfer can produce equivalent changes in a system. The commonly used conversion is 1.000 kcal = 4186 J.
Quiz questions
Which statement best distinguishes heat from internal energy?Answer: Heat is energy crossing a system boundary because of a temperature difference.
Two objects in thermal contact have reached the same temperature. What condition have they reached?Answer: Thermal equilibrium, with no net heat transfer between them.
Energy enters a substance as it melts, but its temperature stays constant. What does this show?Answer: Energy can be transferred without increasing temperature during a phase change.
A liquid warms when it is stirred. Which explanation best accounts for this change?Answer: Work done on the liquid increases its internal energy.
In a paddle-wheel experiment, falling weights turn paddles in water and raise its temperature. What energy pathway explains this?Answer: The weights' gravitational potential energy is transferred by work, increasing the water's internal energy.
Based on College Physics 2e by Paul Peter Urone, Roger Hinrichs (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.