chpt 8B , 8C, 8D, 8E :)

8 B ) Whats conduction ?

Its simply : transfer of thermal energy through a medium, without the medium moving





DO NOT------->



Conduction occurs when the vibration energy of molecules is transferred from 1 molecule to another.


When comparing metal and non-metal, metals have free electrons that make metal a good conductor of heat. So this explains why good conductor are capable of transferring thermal energy much faster than insulators.


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kk..now after reading what I write, -->metals are capable of transferring thermal energy much faster than insulators, I guess you are capable enough to answer the video question below.


GO CHECK IT OUT !

GOT IT RIGHT ?

• How about the conduction in liquid ? Are they the same?
  

ANS: Obviously not ! ! haha. As the particles in liquid are further apart compared to solid

Lets check out this video which is somewhat similar to the TB experiment on pg 133(can refer while watching, this makes you understand better..muhahaha)



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8 C )

----Whats ----

convection
?????ha???ha??????

Frankly speaking, I did not understand what the TB was saying until I see this video and can visualise better

Convectional is the transfer of heat energy involving material of GAS OR LIQUID ONLY.

CONVECTION PROCESS

1. Air above candle gets heated and expands
   
2. This cause air to become less dense


3. Then,air would rise


4. Replaced with cool air at the end
   

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8 D ) Whats radiation ?

radiation is the emission of infrared waves from surface of all bodies without using medium

Therefore, radiation CAN take place in a vacuum ( RMB? electromagnet waves chapt has stated in 1 of 8 of the properties that they do not require medium)

• good absorbers have dull and black surfaces while poor absorbers have shiny and white surfaces

FACTORS that affect infrared absorption

• SURFACE TEMPERATURE

Higher surface temperature gives higher rate of infrared radiation

• SURFACE AREA
  

Larger surface area gives higher emission of infrared radiation

• COLOUR & TEXTURE

Guess what ? If you don't know this, give a knock on your head..!!

I mention earlier ! The good absorbers must have dull & black surfaces. Therefore, black surface are better emitters .

8 E ) -----APPILCATIONS-----

of thermal energy transfer

Using what we learn in 8B-CONDUCTION-good conductors & insulators

GOOD CONDUCTORS (useful for thermal energy transferring quickly) are used in

• saucepan where direct heat is involved


• Heat exchanger to help save energy by using copper tubes
  

INSULATORS (to minimise loss of thermal energy)are used in

• irons, testube holder in our science lab too !
• sawdust to cover ice blocks
• wollen clothes keeps us warm!

CAN YOU THINK OF OTHER EXAMPLES IN OUR COMMON LIFE ?..there are so many things in the world that we take it for granted

Using what we learn in 8C- CONVECTION
(its exactly what we learn in 8C)

*electric kettles - The bottom heating coil is placed bottom to aid transfer of thermal energy in water by convection.

1. The heating coil heats up, expands & become less dense


2. The heated water then rise
   
3. The cooler upper part descend to replace the heated water.
   

*Refrigerator works just as the same way ;D

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Using what we learn in 8D- RADIATION

teapots- As mentioned, the shinier the surface, the worse emitter radiation it will be. Therefore, the shiny teapots can be kept warm.

NEXT TIME WHEN YOU BECOME MOTHER PLS KNOW HOW TO BUY GOOD TEAPOTS =)

wah!!! the 2 teapots so sweet.. especially its my FAV PINK ! I WAN !!!

Actually, I like the 2nd one better..
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VACUUM FLASK- 四全其美

It can keep liquid hot by minimising heat loss using- CCR and evaporation.
(not CPR pls..)



haha.. QWERTYUIOPAS}DWAFMLX")*)(#%

AS YOU KNOW

"PICTURE SPEAKS
A THOUSAND WORDS"
DBVXCNBMKXLAZXCVNBM
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