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heat, movement of heat - Coggle Diagram
heat
effects
expansion
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laboratory glassware
the thick walls of some glassware are likely to crack under hot temperatures, so test tubes made of thin glass are usually used to heat chemicals
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opening a jar
when a jar lid is too tight, the lid is heated to allow the lid to expand more than the glass jar, causing the lid to loosen and be opened.
rivets
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- when red hot, the rivet is put into position.
- it is hammered into a head and then allowed to cool
- as the rivet cools, it contracts and pulls the steel plates together
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bimetallic strips
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the brass expands more than the iron when heated. hence the heated strip bends with the brass on the outside of the curve.
when cooled, the brass contracts more than the iron, causing the strip to bend with the iron outside of the curve
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expansion
it is when heat is applied to a substance, the substance increases in volume, causing it to expand
heat applied increases, expand more
contraction
it is when a substance is cooled, the substance decreases in volume, cauing it to contract
cool down more, contract more
movement of heat
conduction
it is the process of heat transfer through a medium or material without any movement of the medium or material
a material that conducts heat is called heat conductor. some materials conduct heat better than others. bad conductors of heat are called insulators
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good conductors of heat : metals, steel, iron
bad conductors of heat : wood, plastic, glass, water, air and rubber
uses of heat conductors
cooking utensils like pans, pots and kettles
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convection
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a fluid of lower density rises in a fluid or higher density. a fluid will sink when it is in a fluid of lower density
how water heats up: the water at the bottom is closer to the heat source, gain heats and become less dense than the water at the top, so it rises up. the water at the top is further from the heat source it gains heat slower than the water at the bottom so it becomes denser than the water at the bottom. since its denser, it sinks to the bottom, and the whole cycle repeats with water at the water rising, top sinking until all the water is heated up
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the denser the liquid the more it sinks, the less dense the liquid, the more it rises up
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radiation
it is the transfer of heat in the form of waves, from one place to another. it does not require a medium for transmission
the hotter the body, the higher the radiation
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uses of radiators
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shiny, polished utensils are bad radiators of heat so their contents can be kept hot
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