Why Are Heat and Cold Important We need heat for so many things in our lives Do you start the day with a warm shower The shower water has to be heated If you have toast for breakfast you need heat to make it If you travel to school by car or bus the engine needs heat to work These examples are just the beginning of the story Most electricity is made in power plants that run on heat 쑼 In a blast furnace iron ore is heated until the iron is molten It can then be separated from the solid slag waste Using Heat Metals must be heated to get them out of the rocks where they are found Plastics are made from oil a process that uses lots of heat Even this book needed heat to make it The paper is made from wood that was cooked in water and chemicals 4
Cooling Down Heat is not always useful Sometimes we need to cool things down Fridges and freezers keep food cold so it lasts longer without going bad Fridges in hospitals keep medicines and vaccines fresh Many engines and machines have to be cooled or they overheat and do not work properly Even people need cooling We sweat to stay cool in hot weather Studying Heat and Cold In this book you will learn some of the amazing things scientists have found out about heat and cold Humans are warmer than their surroundings because mammals generate heat inside their bodies Our bodies produce surprising amounts of heat In just 15 minutes an adult gives off enough heat to boil more than 2 pints 1 liter of water A young person being smaller gives off less heat 쑿 A thermogram is a special picture that shows how much heat an object or living thing gives off Hot areas appear red or yellow colder areas green or blue 5
