This document discusses different methods of heat transfer. It explains that heat flows from warmer to cooler regions. Conduction involves heat transfer through a medium without the medium moving. Good conductors like metals allow heat to move quickly, while insulators block heat transfer. Convection involves heat transfer through the movement of fluids like liquids and gases. Hot fluids rise and cooler fluids sink, circulating heat through the medium. Conductors and insulators have many applications based on their abilities to transfer or block heat.

1. Heat is useful form of thermal energy transfer .
Heat / thermal energy flows from region of higher temp. to region of lower temp.
Conduction
 One end of metal rod heated , other end heat up after some times -> heat moves from
one end of rod to another-> movement of heat through a medium without medium
moving is Conduction
 Process of heat transfer through a medium or material without any movement of the
medium or material
 A material that conducts heat is called Conductor , some material conduct better than
others
Eg. Metal spoon heats up in hot water but not plastic spoon
Eg. Hot weather metal bench become too hot to sit on but still can sit on wooden bench
 Test for good/bad conductors
At room temp. , some objects warm to touch while others cooler
Norm. body temp. is 37°C , but room temp. is 30°C so heat conducted away from body
when in contact with objects in the room
Copper , brass , iron , glass ,wood ( best conductor of heat to worst )
Pg. 187 ( bottom science bites ) -> why metals are better conductors
 Good conductors
Metals ( Gold , brass , chromium , iron , lead ) -> highest thermal conductivity to lowest
among metals
Pg. 188 ( middle – explanation )
Pg. 188 ( bottom – uses of conductivity of metal )
 Bad conductors of heat
Wood , rubber , asbestos , plastic , glass, water , air bad conductors / insulators
Water , plastic , wood , Styrofoam , air ( best to worst conductor )
Block heat from being transmitted from one place to another
Most liquids ( except mercury ) is bad conductor
Uses of heat conductors and insulators
Conductor
- Cooking utensils conduct heat quickly from fire to food / water inside
Eg. Frying pans , saucepans , kettles , pots
- Radiators warm air around them and conduct heat away from heat source so they made of
metal
Insulator
- Used to make handles of cooking utensils so person holding are in comfort
- Walls , doors , lids of ovens , vacuum flasks , ice cream carts , ice boxes , refrigerator made of
insulator to keep heat in / out

2. - Walls of buildings made of brick / non-conducting material so heat is kept out of air-
conditioned house / heat kept in if house in very cold climate
- Oven gloves , table mats , sunshields , toilet seats , picnic food carriers , ground mats ,
protect body from hot/cold surface
Convection
- Liquid and gases are poor conductors but transfer heat by convection
- Transfer of heat from one place to another by movement of fluids . A fluid given density rise
within a fluid of greater density and sinks within in a fluid of smaller density .
- Fluid is liquid/gas
- Take place due to expansion of fluid , when fluid hot , volume increases and density
increases
- Less dense liquid rise and float and denser liquid flows in to take its place
Convection in liquid
- Beaker of water heated , hot water from bottom rise to top
- Redaced by cold water from top moving down.
- Heat carried from one place to another by movement of water .
- Pg. 191 ( bottom – movement of convection current from bottom to top )
Convection in gas
- Pg. 192 ( top – experiment 6 explanation )
- Coal mines ventilated by vertical shafts sunk into mines joined by horizontal passages where
fire lit at bottom of one shaft so hot air rise and cold fresh air enter