Heat For Beginners (1970)

thank you the Sun is hot it gives off heat can you think of other things that give off heat thank you we know some things that give off heat don't we but how do we know that's one way of telling isn't it we can tell by how heat feels can you think of another way of telling when something gives off heat [Music] thank you we can boil water with heat what about heat from the Sun is there a way of boiling water with heat from the Sun perhaps if we focus the sunlight with a magnifying glass [Music] thank you heat from the Sun boils water with some ice frozen water and some other heated water we can learn about something else heat does what happens as the heated water is poured on the ice heat passes from the hot water to the cold ice the hot water becomes cooler the ice becomes warmer and melts can you think of other things that melt when they're heated making things melt this is a way heat changes things what will happen to the melted wax when it cools it becomes hard once again here's a solid piece of lead a kind of metal can it be melted too it takes a lot of heat to melt lead now we're pouring the melted lead into a mold what do you suppose will happen to the lead inside the mold now the lead is cooler it is formed tiny figures figures of solid lead like other materials we've seen becomes a liquid when heated then becomes a solid once again when cooled what other things happen to solids when they're heated we can find out with a solid aluminum rod with a balloon near one end the balloon is almost touching the end of the rod which has a sharp point if the rod were longer it would break the balloon what might cause the rod to get longer to expand will heat do it foreign heat made the metal expand what about a liquid will the liquid in this flask expand when heated the liquid Rises into the tube the liquid expands when heated now watch as heating stops the liquid goes back down again doesn't it as the liquid cools it shrinks back into the flask the way it was before it was heated what about gases gases that make up air there is air in the bottle and Air in the plastic bag will Air expand when heated [Music] air expands when it's heated what about when it's cooled [Music] the air goes back to the way it was a marshmallow shows us another way he changes things will the marshmallow ever change back to the way it was before it was cooked you've probably seen heat used to make popcorn will the popped corn ever change back to the way it was before it was popped what about some eggs when they're heated will they ever change back to raw eggs again now let's think about something else how heat gets to the eggs through the metal pan how fast does heat pass through metal we'll do an experiment with a piece of metal and a pad of soft material the same thickness as the metal will heat pass through the soft PAD as quickly as through the metal let's find out on top of each we'll place a glass dish add in each dish an ice cube heat passes very quickly through the metal melting the Ice Cube the metal is a conductor of heat the Ice Cube on the pad isn't melting as fast it takes much longer for heat to pass through the pad of soft material it's a kind of insulation we wouldn't use insulation to make a frying pan we use a conductor metal conducts heat quickly to all parts of the pan including the handle there's a danger of getting burned if we grab the handle directly a pad made of insulating fabric protects our hand can you think of other insulating materials we use gloves insulate our hands from the cold another use of insulation is in the walls of a house insulation is placed in walls of many homes when they're built on hot summer days insulation keeps heat from moving into a house keeping it cool inside in the winter insulation keeps heat from moving out of the house keeping it warm inside can you see how insulation might make a home more comfortable can you think of some other uses for insulation it helps to know which things are heat insulators and which things are heat conductors what else can you remember about heat what are some ways he changes things [Music] what things give off heat [Music] how much can you remember about heat and what it does [Music]