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Heat (Ri Tong) - Coggle Diagram
Heat (Ri Tong)
CONDUCTION
What is conduction?
The process of heat transfer through a medium without the movement of the particles in the medium
How?
Vibration of particles
Motion of free electrons
Conductors of heat
Good
Materials that allow heat to flow through easily
Metals
Bad
Materials that do
not
allow heat to flow through easily
Glass
Plastics
Wood
Mechanisms
Vibration of particles
Particles in solids are closely packed
Particles in solids can only vibrate at fixed positions
When heated the particles
gain heat energy
& vibrate
more vigorously
Heat energy is transferred from particle to particle
slow process
Free electrons
Metals
have free electrons
Free electrons move freely
Help to transfer heat energy
Transfer heat to cooler regions
quickly
Metals are much better heat conductors
Different metals conduct heat at different speeds
Fast process
Applications
Good conductors
Cooking utensils
Made of metals
Conduct heat quickly to cook the food
Cars & buses
Radiators made of copper
Conduct heat quickly to heat up water
Heating element in kettles
Made of metal
Conducts heat quickly to heat up water
Poor conductors
Utensil handles
Made of insulators
protect hands from scorching when holding them during cooking
Woollen jacket
Traps air
Prevents heat loss from the body to cold surroundings
CONVECTION
What is convection?
The process of heat transfer through a medium by the movement of the particles in the medium
It can only take place in liquids and gases
Why?
The particles in fluids are able to move freely
Thus transferring heat from one region to another
Convection current
How?
When a region of the fluid is heated
particles move faster & spread out
Volume increases
density decreases
mass of the particles remains constant
The
hot
fluid
rises
and
cold
fluid
sinks
Heat transferred in a circulatory motion
It is set up due to a change in the density of the fluid
Experiments
Liquid
Water is heated and expands
Density decreases
Rising up
Cooler part of the water is
denser
Sinks to replace hot water
Gas
Air is heated and expands
Density decreases
Rises out of the chimney
Cooler surrounding air is denser
Sinks to replace the hot air
Applications
Electric kettle
Heating element at the bottom
Heats up water
Hot water rises and cold air sinks
Water is heated more uniformly and effectively
Hot water system
Boiler at the lower part
Water is heated up
Hot water rises to the upper part
Cold water sinks into the boiler replacing the hot water
Air conditioner
Placed at the top of a wall
Cold air sinks into the room
Hot air rises
Cooled by the air conditioner
Sinks down
Cooling the room efficiently
Natural Phenomena
Sea breeze
Land is heated up faster
Air above the land is warmer
It rises up
Cooler and denser air from the sea
replaces rising hot air
Land breeze
Land loses heat much faster
Air above the sea is warmer
It rises up
Cooler and denser air from land
Replacing rising hot air
HEAT FLOW
What is heat?
Heat is a form of energy
Hear flows from a region of
higher temperature
to a region of
lower temperature
The region of
higher temperature
is often referred to as a
heat source
The region of
lower
temperature is referred to as the
heat sink
what happens when an object
gains
heat?
The temperature of the object
increases
The object changes in
size
or
physical state
What is temperature?
The measure of hotness and coldness of an object
The greater the temperature difference the faster heat flows