Heat

Heat book cover — CONTENTS INTRODUCTION CHAPTER 1 WHAT is HAT 10 CHAPTER 2 MEASURING TEMPERATURE 20 CHAPTER 3 MEASURING HEAT 30 38 CHAPTER 4 How HEAT is TRANSFERRED 2 TL 1 50 CHAPTER 5 THERMODAMICs m 65 67 CoNaUSON Go SARY FOR MORE INFORMATION BIBLIOGRAPHY INDEX 70 73 74

Heat — page 1 — he sting we feel after touching a hot pan the welcome reliefоf a cold drink on a warm day and the comfort of a heater as it thaws our frozen limbs are sensa tions that are familiar to most of us indeed hotness and coldness texture a number of our everyday experiences We may throw around terms such as heat and temperature casually in conversation to describe what we perceive in such situations but physics shows us that these are not interchangeable terms As you will discover in these pages we must begin at the atomic level of matter to understand heat and the related concepts of temperature and thermal energy as well as the relationships between them In physics the term heat refers to the energy that is transferred from a warmer object to a colder one The energy that is transferred must of course come from some where In fact it all starts with the atoms and molecules that compose all matter Each of these particles is constantly moving and gen erating energy from this motion This is called kinetic energy The total amount of kinetic energy an object has is equal to its thermal energy that is the energy that an object has stored as a result of its temperature To

Heat — page 2 — INTRODUCTION illustrate let's consider a pot of soup and a cup of soup ladled from it The thermal energy of the pot is greater because it has more particles that are moving and creating energy Temperature represents the average speed of all the particles in an object the faster its particles move the higher its tem perature will be Unlike thermal energy temperature does not depend on the quan tity of the substance In the case of the pot and cup of soup the average speed of the particles may be the same in both thus giv ing them the same temperature even though they differ in size In most instances when heat is trans ferred from a warmer substance to a colder one the temperature of the warmer sub stance will decrease while that of the colder one will increase This will continue until the two are at the same temperature At other times however heat transfer may not cause a change in temperature at all rather the mol ecules of the heat absorbing substance may change and rearrange themselves in what is called a phase change One example of this is the change of water to vapor as it is heated Both temperature and heat can be mea sured The Fahrenheit and Celsius

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