7.2 heat flow
TRANSCRIPT
![Page 1: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/1.jpg)
7.2HEAT FLOW AND
ITS EFFECT
![Page 2: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/2.jpg)
EXPANSION OF METALS CAUSES BY HEAT
Metal expand when they are heated. Metal contract when they are cooled.
The iron ball can pass through the ring
before heating
After heating, the metal ball cannot
pass through the ring
![Page 3: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/3.jpg)
When a metal is heated, its particles receive more energy and vibrate faster.
The particles occupy more space and move further apart from one another. So the metal expands.
On cooling, the vibrations slow down and the particles return to their original position. So the metal contracts.
![Page 4: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/4.jpg)
Metal expands when heated
![Page 5: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/5.jpg)
Metal 1 : ironMetal 2: copper
Different metal expand different amount when heated
![Page 6: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/6.jpg)
AluminiumBrassCopperIronZinc
Expands most
on heating
![Page 7: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/7.jpg)
EXPANSION OF LIQUID CAUSED BY HEAT
Liquid expand when they are heated. Liquid contract when they are cooled.
![Page 8: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/8.jpg)
When a liquid is heated, its particles receive more energy and vibrate faster.
The water molecules occupy more space and move further apart from one another. So the liquid expands.
On cooling, the vibrations slow down. So the liquid contracts.
![Page 9: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/9.jpg)
Coloured water
Water level before heating
Water level after heating
![Page 10: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/10.jpg)
The water level in the glass tube falls a little at first because the flask expands before the water.
Liquid expand more than metals for the same rise in temperature.
Different liquids expand different amount when heated.
![Page 11: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/11.jpg)
AlcoholOilWater
Expands moston heating
Different liquid expand different amount when heated
![Page 12: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/12.jpg)
Different liquid expand different amount when heated
Water
Oil
Alcohol
![Page 13: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/13.jpg)
EXPANSION OF GAS CAUSED BY HEAT
Gas expand when they are heated. Gas contract when they are cooled.
![Page 14: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/14.jpg)
![Page 15: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/15.jpg)
When the air is warmed, the gas particles receive more kinetic energy and move outwards very quickly in all direction.
Gases expand very fast because there is:a) Plenty space between the particlesb) Force of attraction between particles are
very weak. All gases expand at about the same rate
when heated.
![Page 16: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/16.jpg)
Principle of heat transfer
1. Conduction : through solid2. Convection : through fluid (liquid or gases)3. Radiation : through empty space
High temperature Low temperature
3 ways of heat transfer
![Page 17: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/17.jpg)
CONDUCTION Definition: movement of heat through a
solid from a hot part to a cooler part. Metals are good conductors of heat. Non-metal are bad conductors (insulators)
of heat.
![Page 18: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/18.jpg)
CONDUCTION When the hot end of a metal rod is
heated, the particles receive more energy and vibrate faster.
The more active vibrating particles knock their neighbours. So heat is transferred along the metal rod.
![Page 19: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/19.jpg)
Conductors Insulators
SilverCopperGoldAluminiumIronTinLeadMercury
Very good
Good
VacuumAirCorkPlasticWoodGlassAsbestosWater
![Page 20: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/20.jpg)
![Page 21: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/21.jpg)
![Page 22: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/22.jpg)
Application in daily life
![Page 23: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/23.jpg)
CONVECTION Definition:
movement of heat through a fluid by the movement of the fluid particles.
Liquid and gases are referred as fluid.
![Page 24: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/24.jpg)
When a fluid is heated, it expands and become less dense.
The heated fluid rises, and cooler fluid flows down.
Convection cannot take place in solid because the particles in solid cannot move freely.
![Page 25: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/25.jpg)
![Page 26: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/26.jpg)
![Page 27: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/27.jpg)
![Page 28: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/28.jpg)
![Page 29: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/29.jpg)
![Page 30: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/30.jpg)
Convection in a liquid Convection in a gas
![Page 31: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/31.jpg)
![Page 32: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/32.jpg)
Application of convection Electric kettle Refrigerator
![Page 33: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/33.jpg)
Application of convection Ventilation
system Car radiator
![Page 34: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/34.jpg)
Application of convection Sea breeze Land breeze
![Page 35: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/35.jpg)
Sea breeze During the day, the
land is much hotter than the sea.
Hot air above the land rises, and cooler air from the sea moves in to take its place.
Land breeze At night, the land
become colder than the sea.
Hot air above the sea rises, and cooler air from the land moves in to take its place.
![Page 36: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/36.jpg)
![Page 37: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/37.jpg)
Radiation Radiation is the transfer of heat without
using a medium. Radiated heat can travel through a
vacuum. Ex: 1. Heat from the sun travels through a
vacuum in outer space to the Earth.2. Scouts sitting around a camp fire.
![Page 38: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/38.jpg)
Radiation of heat
![Page 39: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/39.jpg)
Application of heat transfer- the thermos flask-
Stopper: made up of cork/plastic (heat insulator).
Glass wall: inner surface of the wall are silvery and reduce heat transfer by radiation.
Vacuum: stop conduction and convection.
Base: made up of cork (heat insulator).
![Page 40: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/40.jpg)
Silvered on inside
Contents
Vacuum
Outer container
Screwed top
![Page 41: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/41.jpg)
![Page 42: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/42.jpg)
![Page 43: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/43.jpg)
![Page 44: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/44.jpg)
![Page 45: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/45.jpg)
![Page 46: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/46.jpg)
![Page 47: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/47.jpg)
![Page 48: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/48.jpg)
![Page 49: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/49.jpg)
![Page 50: 7.2 heat flow](https://reader035.vdocument.in/reader035/viewer/2022062306/577cced01a28ab9e788e55ef/html5/thumbnails/50.jpg)