Thermodynamics

1. Thermodynamics Thermodynamics is the study of the transfer of energy, as heat. Internal energy of a substance is the total kinetic energy of a substance due to the motion of the particles in the substance.

2. Temperature Temperature measure of the average internal kinetic energy of the particles in a substance. Measure of internal energy within a substance Measure of how much the atoms and molecules of a substance are moving. Temperature changes only when energy is added or removed. This is known as heat.

3. Thermometer Thermometer instrument used to measure temperature. “Thermos” means heat and “metros” to measure. The most common thermometers use a glass tube containing a thin column of mercury, or alcohol. Energy is absorbed, and the volume of the liquid expands up the glass column.

4. Temperature Scales Three different types of scales used for measuring temperature. Fahrenheit ScaleCreated by German physicist, Daniel Gabriel Fahrenheit (1686-1736) in 1724. Set the freezing point of water at 32° and the boiling point at 212°. With these two points the bases were created 180 degrees apart. Celsius Scale Proposed by Swedish astronomer, Anders Celsius (1701-1744) in 1743. Using the same idea, he determined the freezing temperature for water to be 0° and the boiling temperature 100 °.The Celsius scale is the most used in the world. Kelvin ScaleProposed by William Thomson, Lord Baron Kelvin. This scale is based on absolute zero with 273.15 K for the freezing point, and 373.15 K for the boiling point, of water.

5. Temperature Scales Uses Temperature is measured in degrees on the Fahrenheit, Celsius, and Kelvin scales.

6. Absolute Zero William Thomson, Baron Kelvin. Understood that there was a limit to how cold something can be. The Kelvin scale goes to a temperature of Absolute Zero-the temperature at which nothing could be colder and no heat energy remains in a substance — there is no motion and no kinetic energy. Absolute zero is where all molecular motion stops and is the lowest temperature possible. Absolute Zero occurs at 0 Kelvin or -273.15°C at -459.67° Fahrenheit Absolute zero has never been reached. The closest laboratory experiments have reached is a temperature of 0.000001 K.

9. Temperature Conversions • Celsius to Fahrenheit °F = (°C 9/5) +32 • Fahrenheit to Celsius °C = (°F-32) (5/9) • Celsius to Kelvin K = °C + 273.2 • Kelvin to Celsius °C = K - 273.2 U.S. Weather http://www.weather.com/weather/local/79936?lswe=79936&lwsa=WeatherLocalUndeclared&from=whatwhere Mexico Weather http://www.meteored.mx/clima_Ciudad+Juarez-America+Norte-Mexico-Chihuahua-MMCS-1-22387.html

10. Conversion Examples K = °C + 273.15         K = °19 + 273.15 K = 292.15 °C = (°F-32) (5/9)     °C = (°78-32).556 °C = 25.57° °F = (9/5)(°C) +32   °F = (1.8)(°11)+32 °F= °51.8

12. Heat Heat (Q) is the transfer of energy (given up or absorbed) between objects because of a difference in their internal energies, or temperatures. The direction in which energy travels as heat can be explained at the atomic level. Energy transferred as heat always moves from an object at higher temperature to an object at lower temperature.

13. Heat Exchange Heat may be transferred from one substance to another three ways: conduction, convection, and radiation. When two objects reach equal temperatures, this is known as thermal equilibrium.

14. Conduction Conduction transfer of heat energy by direct contact • Conduction involves the transfer of energy from one molecule to adjacent molecules without the substance as a whole moving. (Particularly a transfer for solids)

15. Convection Convection is the transfer of heat energy in circular currrents due to change in density, takes place in fluids i.e., liquids and gases

16. Radiation is the transfer of heat energy in the form of electromagnetic radiation, specifically infrared waves,. Radiation

17. Specific Heat Capacity Specific Heat Capacity (C) The quantity of energy needed to raise the temperature of 1kg of a substance by 1˚C at constant pressure. Since different substances have different compositions, different substances have different heat capacities. Specific Heat Capacity = energy transferred as heat mass × change in temperature C = Q/(mΔT) units: J/(kg˚C)

18. Specific Heat Capacities The high specific heat of water plays an important role in temperature regulation.

19. Heat Heat (Q) is the measure of the exchange of energy. It is dependent on the mass of the substance, the specific heat capacity, and the change in temperature Q = mCDT units: kg (J/(kg˚C) ˚C = JOULES Calorie (cal) is the quantity of heat required to raise the temperature of one gram of water one degree Celsius. 4.186 Joules = 1 cal British thermal unit (Btu) English unit commonly used in the United States

20. Thermal Units

22. Thermal Equilibrium • Thermal equilibrium is the basis of measuring temperature with thermometers • Ex: Can of warm fruit juice immersed in a large beaker of cold water After 15 minutes, the can will be cooler and the water will be slightly warmer Eventually they will be at the same temperature. This is an example of thermal equilibrium. Energy transferred as Heat travels from objects of higher temperature to objects of lower temperature.

23. Thermal Expansion the tendency of matter to change in volume in response to a change in temperature. Thermal Expansion Thermometers are an example of thermal expansion- most contain a liquid which is constrained to flow in only one direction (along the tube) due to changes in volume brought about by changes in temperature.