13.1 Temperature
3 min read•june 18, 2024
and are fundamental concepts in physics. They describe how hot or cold objects are and the energy associated with their particles' motion. Understanding these ideas is crucial for grasping heat transfer and thermodynamics.
Temperature scales like , , and help us measure and compare temperatures. Converting between these scales is essential for practical applications and scientific research. The concept of , the lowest possible temperature, is a key principle in thermodynamics.
Temperature and Thermal Energy
Temperature and thermal energy
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- Temperature measures the average kinetic energy of particles in a substance
- Higher temperature indicates particles have higher average kinetic energy (boiling water)
- Lower temperature means particles have lower average kinetic energy (ice cube)
- represents the total kinetic energy of all particles in a substance
- Depends on both temperature and the number of particles or mass (cup of coffee vs. pot of coffee)
- Objects with the same temperature can have different thermal energies if they have different masses (ice cube vs. iceberg)
- is the amount of heat required to raise the temperature of an object by one degree
- is the heat capacity per unit mass of a substance
Conversion of temperature scales
- Celsius (°C) and Fahrenheit (°F) are relative temperature scales, Kelvin (K) is an absolute scale
- Convert between Celsius and Fahrenheit:
- Convert between Celsius and Kelvin:
- Convert between Fahrenheit and Kelvin:
- is the lowest possible temperature, corresponding to 0 K or -273.15°C
Thermal Equilibrium and the Zeroth Law of Thermodynamics
Thermal equilibrium in heat transfer
- occurs when two or more systems in thermal contact have the same temperature
- No net heat transfer happens between systems in (room temperature coffee and air)
- Heat always flows from higher to lower temperature system
- Temperature difference determines the direction of heat transfer (hot coffee to cold mug)
- When systems with different temperatures are in thermal contact, heat flows until thermal equilibrium is reached (ice melting in warm water)
Zeroth law of thermodynamics
- States if two systems are in thermal equilibrium with a third system, they are also in equilibrium with each other
- Allows defining temperature and establishing temperature scales (Celsius, Fahrenheit, Kelvin)
- Practical applications:
- Thermometers: Zeroth law enables calibrating thermometers using fixed points (freezing and boiling points of water)
- Thermostats: Zeroth law allows thermostats to control temperature in devices (ovens, refrigerators, HVAC)
- Thermal insulation: Zeroth law helps understand the effectiveness of insulation materials in preventing heat transfer (fiberglass, foam)
Thermal Effects
- Thermal expansion occurs when materials increase in size as temperature increases
- is the energy absorbed or released during a phase change without changing temperature
Key Terms to Review (20)
Absolute zero: Absolute zero is the theoretical lowest temperature possible, where all molecular motion ceases. It is equal to 0 Kelvin or -273.15 degrees Celsius.
Absolute Zero: Absolute zero is the lowest possible temperature on the temperature scale, where the motion of atoms and molecules reaches its minimum. It is the point at which a system reaches its coldest state and has profound implications in the study of temperature and the kinetic theory of gases.
Celsius: Celsius is a temperature scale that measures the degree of hotness or coldness of an object or environment. It is commonly used in scientific and everyday applications to quantify temperature and its changes.
Critical temperature: Critical temperature is the highest temperature at which a substance can exist as a liquid, regardless of pressure. Beyond this temperature, the substance becomes a supercritical fluid.
Degree Fahrenheit: The degree Fahrenheit (°F) is a unit of temperature used primarily in the United States. It is based on a scale where the freezing point of water is 32°F and the boiling point is 212°F under standard atmospheric conditions.
Fahrenheit: Fahrenheit is a temperature scale that measures the degree of heat or cold. It is commonly used in the United States and a few other countries, with the freezing point of water at 32°F and the boiling point at 212°F under standard atmospheric pressure.
Heat Capacity: Heat capacity is a measure of the amount of energy required to raise the temperature of a substance by a certain amount. It quantifies how much heat a material can absorb or release without undergoing a significant change in temperature. This concept is crucial in understanding the thermal properties of materials and their behavior during various thermodynamic processes.
Kelvin: Kelvin is the SI base unit for temperature, symbolized as K. It measures absolute temperature starting from absolute zero.
Latent Heat: Latent heat is the energy released or absorbed by a substance during a phase change, such as the transition from solid to liquid or liquid to gas, without a change in temperature. It is the energy required to change the physical state of a substance while maintaining a constant temperature.
Latent heat coefficients: Latent heat coefficients represent the amount of heat required to change the phase of a unit mass of a substance without changing its temperature. They are crucial in understanding phase changes like melting, freezing, boiling, and condensation.
Specific heat: Specific heat is the amount of heat energy required to raise the temperature of one unit mass of a substance by one degree Celsius. This property varies among different materials and is crucial in understanding how substances respond to heat changes, affecting processes like heating, cooling, and energy transfer.
Temperature: Temperature is a physical quantity that measures the average kinetic energy of the particles, such as atoms or molecules, in a substance. It is a fundamental concept that is closely related to the behavior of matter and energy in various contexts, including vectors, scalars, coordinate systems, the ideal gas law, kinetic theory, and phase changes.
Thermal energy: Thermal energy is the internal energy of a system due to its temperature. It arises from the random motions of atoms and molecules within the system.
Thermal Energy: Thermal energy is the total kinetic energy of the random motion of the particles (atoms and molecules) that make up a substance. It is a measure of the internal energy of a system due to the vibration and movement of its atoms and molecules. Thermal energy is a fundamental concept that connects the topics of nonconservative forces, conservation of energy, power, world energy use, temperature, kinetic theory, heat transfer, and the second law of thermodynamics.
Thermal equilibrium: Thermal equilibrium is the state in which two or more objects in contact do not exchange heat, meaning they are at the same temperature. No net heat flow occurs between them.
Thermal Equilibrium: Thermal equilibrium is a state where two or more objects or systems have the same temperature and no net heat transfer occurs between them. This concept is fundamental in understanding the behavior of temperature, heat, and thermodynamics.
Thermometer: A thermometer is a device used to measure and indicate temperature. It is a fundamental tool in the study of temperature, a crucial physical quantity that describes the degree of hotness or coldness of an object or environment.
Thermostat: A thermostat is a device that automatically regulates temperature by switching heating or cooling systems on or off to maintain a desired setpoint. It plays a crucial role in controlling indoor climates, ensuring comfort while also promoting energy efficiency by adjusting system operations based on environmental conditions.
Zeroth law of thermodynamics: The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This principle allows for the definition of temperature.
Zeroth law of thermodynamics: The Zeroth law of thermodynamics establishes a foundational principle of thermal equilibrium, stating that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law forms the basis for the concept of temperature, allowing it to be defined and measured consistently across different systems.