Introduction to thermodynamics Prof. Marlon Flores Sacedon Department of Mathematics and Physics College of Arts and Sciences Visayas State University, Visca Baybay City, Leyte, Phiippines

What is Thermodynamics? Thermodynamics is a study of energy transformations involving heat, mechanical work, and other aspects of energy and how these transformations relate to the properties of matter.

Temperature and Heat Temperature is rooted in qualitative ideas of “hot” and “cold” based on our sense of touch cold. A body that feels hot usually has a higher temperature than a similar body that feels cold.

Temperature and Heat System A System B System C Insulator Conductor System A System B System C Conductor Insulator System A System B System A System B System C (b) …then A and B are in thermal equilibrium with each other. (a) If system A and B are each in thermal equilibrium with system C… If C is initially in thermal equilibrium with both A and B, then A and B are also in thermal equilibrium with each other. This result is called the Zeroth Law of thermodynamics Zeroth Law of Thermodynamics Two system are in thermal equilibrium if and only if they have the same temperature.

Temperature scale Celsius Fahrenheit Kelvin Rankine Units of Temperature Celsius Fahrenheit Kelvin Rankine

Temperature scale Temperature Scale At freezing Point of water Celsius and Fahrenheit relationship Temperature Scale At freezing Point of water At boiling point of water Celsius , Tc 0 oC 100 oC Fahrenheit, TF 32 oF 212 oF 𝒎= 𝒓𝒊𝒔𝒆 𝒓𝒖𝒏 = 𝟏𝟖𝟎 𝒐 𝑭 𝟏𝟎𝟎 𝒐 𝑪 = 𝟗 𝒐 𝑭 𝟓 𝒐 𝑪 TC TF 212 oF 100 oC Linear function 𝒚=𝒎𝒙+𝒃 𝑻 𝑭 = 𝟗 𝒐 𝑭 𝟓 𝒐 𝑪 𝑻 𝑪 +𝟑𝟐 𝒐 𝑭 𝟏𝟖𝟎 𝒐 𝑭 32 oF 𝑻 𝑭 = 𝟗 𝟓 𝑻 𝑪 +𝟑𝟐 𝟏𝟎𝟎 𝒐 𝑪 𝑻 𝑪 = 𝟓 𝟗 𝑻 𝑭 −𝟑𝟐

Temperature scale Kelvin scale The kelvin is a unit of measure for temperature based upon an absolute scale. It is one of the seven base units in the International System of Units (SI) and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics.

Temperature scale 𝑻 𝑲 = 𝑻 𝑪 +𝟐𝟕𝟑.𝟏𝟓 Kelvin scale 𝑷 𝑻 𝒐 𝑪 𝟎 𝟏𝟎𝟎 𝟐𝟎𝟎 𝑻 𝒐 𝑪 𝟎 𝟏𝟎𝟎 𝟐𝟎𝟎 −𝟏𝟎𝟎 −𝟐𝟎𝟎 Gas Thermometer 𝟐𝟕𝟑.𝟏𝟓𝑲 −𝟐𝟕𝟑.𝟏𝟓 𝒐 𝑪 𝑻 𝑲 𝟏𝟎𝟎 𝟐𝟎𝟎 𝟑𝟎𝟎 𝟒𝟎𝟎 5𝟎𝟎 𝟎 𝟎𝑲=−𝟐𝟕𝟑.𝟏𝟓 𝒐 𝑪 𝟎 𝒐 𝑪 =𝟐𝟕𝟑.𝟏𝟓𝑲 = 𝟓 𝟗 𝑻 𝑭 −𝟑𝟐 +𝟐𝟕𝟑.𝟏𝟓 𝑻 𝑲 = 𝑻 𝑪 +𝟐𝟕𝟑.𝟏𝟓

Temperature scale Instantaneous Temperature, (𝑇) Degree celsius, (𝑜𝐶) Degree Fahrenheit (𝑜𝐹) ∆𝑻= 𝑻 𝒇𝒊𝒏𝒂𝒍 − 𝑻 𝒊𝒏𝒊𝒕𝒊𝒂𝒍 Change in Temperature, (∆T) Degree celsius, ( 𝑪 𝒐 ) Degree Fahrenheit ( 𝑭 𝒐 ) Kelvin (𝐾) 𝟏𝑪 𝒐 =𝟏𝑲 𝟏𝑲= 𝟗 𝟓 𝑭 𝒐 Suppose: 𝑻 𝟏 =𝟑𝟎 𝒐 𝑪 𝑻 𝟐 =𝟖𝟎 𝒐 𝑪 Change in Temperature: ∆𝑻= 𝑻 𝟐 − 𝑻 𝟏 =𝟖𝟎 𝒐 𝑪 −𝟑𝟎 𝒐 𝑪 =𝟓𝟎 𝑪 𝒐 =𝟓𝟎𝑲

Summary of important formulas 𝑻 𝑭 = 𝟗 𝟓 𝑻 𝑪 +𝟑𝟐 Degree Fahrenheit to Degree Celsius 𝑻 𝑪 = 𝟓 𝟗 𝑻 𝑭 −𝟑𝟐 Degree Celsius to Degree Fahrenheit 𝑻 𝑲 = 𝑻 𝑪 +𝟐𝟕𝟑.𝟏𝟓 Kelvin to Degree Celsius 𝟏𝑪 𝒐 =𝟏𝑲 One Celsius degree is equal to one Kelvin 𝟏𝑲= 𝟗 𝟓 𝑭 𝒐 One Kelvin is equal to 9/5 of Fahrenheit degree

Problems 1. Convert the following Celsius temperatures to Fahrenheit: (a) −62.8 𝑜 𝐶 , the lowest temperature ever recorded in North America; (b) 56.7 𝑜 𝐶 , the highest temperature ever recorded in the United States; (c) 31.1 𝑜 𝐶 , the world’s highest average annual temperature. a) -81oF, b) 134.1oF, c) 88oF 2. (a) You feel sick and are told that you have a temperature of 40.2 𝒐 𝑪 . What is your temperature in 𝒐 𝑭 ? Should you be concerned? (b) The morning weather report in Sydney gives a current temperature of 12 𝒐 𝑪 . What is this temperature in 𝒐 𝑭 ? a) 104.4oF;yes, b) 54oF 3. Convert the following Kelvin temperature to the Celsius and Fahrenheit scales; (a) the midday temperature at the surface of the moon (400 𝐾); (b) the temperature at the tops of the clouds in the atmosphere of Saturn (95 𝐾); (c) the temperature at the center of the sun (1.55𝑥 10 7 𝐾)

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