Temperature, Scales, Zeroth Law, Heat Units
Terms you will need
- temperatureTemperature is a measure of how hot or cold something is, based on the movement of its molecules. The higher the temperature, the faster the molecules move.
- celsiusCelsius is a temperature scale where 0 degrees is the freezing point of water and 100 degrees is the boiling point of water at standard pressure.
- fahrenheitFahrenheit is a temperature scale where 32 degrees is the freezing point of water and 212 degrees is the boiling point of water at standard pressure.
- kelvinKelvin is a temperature scale used in science where 0 is the lowest possible temperature, called absolute zero. It has no negative numbers.
- jouleA joule is a unit of energy. It is the amount of energy used when a force of one newton moves an object one meter.
- calorieA calorie is a unit of energy. It is the amount of heat needed to raise the temperature of one gram of water by one degree Celsius.
How this topic runs
Temperature, heat, and energy transfer are central to understanding how the physical world operates. Thermodynamics, the study of energy transformations, began with the question of what heat is and how it can be measured. Temperature is a measure of a body's internal excitation, related to the kinetic energy of its molecules. Heat, on the other hand, is the transfer of energy in a chaotic form between bodies of different temperatures. These concepts are essential for analyzing energy systems, from engines to natural processes. In this chapter, we explore temperature scales, the zeroth law of thermodynamics, and the units used to quantify heat and work. Understanding these fundamentals is crucial for grasping how energy is stored, transferred, and utilized in both natural and engineered systems.
Temperature is a measure of how much the molecules in a substance are moving. The higher the temperature, the faster the molecules move. Temperature is measured in units like kelvins (K), degrees Celsius (°C), or degrees Fahrenheit (°F).
The Kelvin scale is used in science because it starts at absolute zero, the lowest possible temperature where molecules stop moving. Celsius and Fahrenheit are older scales that are still used in everyday life. The zeroth law of thermodynamics says that if two objects are each in thermal balance with a third object, they are in balance with each other.
This helps define temperature as a measurable property. Heat is energy that moves from a hotter object to a colder one. It is measured in joules (J), the same unit used for work.
Understanding these concepts helps explain how energy moves and changes in systems like engines or weather patterns.
Key Points
- Temperature is a body's potential for supplying or receiving heat, indicating its level of internal excitation, with higher kinetic energy of its molecules resulting in higher temperature.
- The Celsius scale (°C) is a temperature scale where a temperature in degrees Celsius is obtained by subtracting 273.15 units from an absolute temperature in kelvins.
- The Fahrenheit scale (°F) is a temperature scale where a temperature in degrees Fahrenheit is calculated using the formula T(°F) = 1.8 × [T(K) − 273.15] + 32.
- The kelvin (K) is the base unit of temperature in the International System of Units, defined as the absolute temperature scale created for thermodynamics.
Terms
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Sources & licensing(4)
- Olivier Cleynen, Engineering Thermodynamics — thermodynamicsbook.com/ (Creative Commons Attribution-ShareAlike 4.0)
- Howard DeVoe, Thermodynamics and Chemistry, 2nd edition — www2.chem.umd.edu/thermobook/ (Creative Commons Attribution 4.0)
- OpenStax — openstax.org/books/university-physics-volume-2/pages/1-1-temperature-and-thermal-equilibrium (Creative Commons Attribution 4.0)
- OpenStax — openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales (Creative Commons Attribution 4.0)