HEAT named after Daniel Gabriel Fahrenheit and Anders Celsius respectively are perhaps the most commonly known and are frequently used on temperature measuring instruments called thermometers Heat changes in a phys ical or chemical reaction can be measured with a device called a calorimeter Anders Celsius for whom the Celsius temperature scale is named Science Source Photo Researchers
INTRODUCTION The process of heat transfer can occur througha few different methods Conduction is heat transfer between adjacent parts of a body or through direct contact between two bodies Convection transfers heat by move ment of a heated fluid such as air or water In contrast heat transfer through radiation requires neither contactnoramedium to carry the energy In this process energy is emitted radiated by a heated surface and travels to another surface where it is absorbed Heat transfer usually involves some combination of all three of these processes The relationships between heat other forms of energy temperature and work form the basis of thermodynamics The three basic laws of thermodynamics describe the nature of these relationships and hold true for all biological and physical systems Indeed much of our understanding of the universe is informed in part by thermodynamics Although we may only think about heat incidentally heat is always around us in one form or another It is critical to all life and our ability to tackle issues in such areas as climate change biology and technology rests on our application of the fundamental concepts you will encounter in this
CHAPTER 1 WHAT IS HEAT eat is so well known from our ear liest childhood that we hardly think about it A steaming bowl of soup an active radiator and a sauna feel hot a book and a chocolate bar at room tem perature seem less hot and an ice cube feels cold In everyday speech it is common to say that the soup has more heat than the book and that the ice cube has less heat than the chocolate bar However people often use the word heat when what they really mean is temperature or a type of energy called ther mal energy Temperature is a measure of hotness or coldness In physics heat refers specifically to energy that is transferred from one thing to another because of a difference in tempera ture If two objects at different temperatures are brought together energy is transferred that is heat flows from the hotter object to the colder one A radiator gives off heat warming the cooler air around it If a per son holds an unwrapped chocolate bar his or her hands transmit heat to the choco late eventually melting it It is incorrect to IO
WHAT IS HEAT speak of the heat in an object itself because I heat is restricted to energy being transferred Energy that is stored in an object because of its temperature is called thermal energy It can be difficult at first to understand the difference between heat temperature and thermal energy To better understand these three related concepts it is helpful to know what actually makes things hot or cold Heat The woman's hand transmits beat to the chocolate barſ which is at a lower temperature than her hand and causes it to melt Westend61 Super Stock II
