INTEGRATED SCIENCE
11 CMH
TEMPERATURE CONTROL
AND
VENTILATION
What is heat ?

Heat is a form of energy.

Heat can transfer from one place to another.

Heat is also known as thermal or internal energy.

Heat always transfer from a hotter place to one that is colder.
What is Temperature?


It is the intensity or the degree of heat in an object or substance.
Temperature is also describe as the amount of heat energy in a
substance.
Methods of Heat Transfer
Conduction

This is the transfer of heat energy through a solid.

The particles of the solid will vibrate continuously (kinetic
energy).

More kinetic movement means higher temperature.

The particles of solid are held closely together.

If one end of a solid is heated its particles will
vibrate a lot gaining more energy.

Nearby particles will now start to vibrate more (get hotter).

Hence heat energy is been transferred through that solid.

For most solid this process is very slow.

Conductors and Insulators
Metals are good conductors of heat.

Liquids and gases normally poor conductors .


Poor conductors such as wood, glass and paper are called good
insulators.
Material which contains trapped air,
such as Styrofoam is a good insulator.
NB Water is a poor conductor of Heat



In the picture below water is believed to be a poor conductor of
heat.
As you can see piece of ice is placed at the base of
the test tube.
When heated the water at the top of the test tube
will boil before the heat is conducted to the water
at the bottom to melt the ice.

Conduction in the Kitchen
Cooking pots are good conductors.

Heat from electrical or gas ring on the stove.



If pot halides are made from metals it will burn you. Hence why
some pot handles are made from insulators such as wood and
plastic.
You will have to use a piece of cloth to hold metal pot
handle to prevent burnt to the hands.
The cloth is a good insulator and a poor conductor of
heat.
Convection


The movement of heat energy through liquids and gases.
The heat is transferred from one part of the substance
to another by movement of the liquid or gas particles
themselves.

Liquid particles are not bound as tightly to each other as solids.

They are able to move so the liquid can flow.

When one part of a liquid is heated, the particles vibrate more
and push each other further apart.


This part of the liquids expands and becomes less dense.
This makes it rise upwards and is replaced by cooler liquid
which is then heated and rises.
Convection Current
 Convection currents are found in:
1. hot water tanks
2. Oven
3. Refrigerators


The heating element is place at
the bottom in hot water tank.
The water at the bottom heats up and rises
upwards.


This is replaced by colder water from the top of the tank.
This convection current will continue until all the water in the
tank is heated.
Sea Breezes
At Day

This is an example of natural convection currents.
During day times the land heats up much faster than the
sea.
 The land then heat the air above it.


The warm air then rises.

Cold air from the sea replace it.

GLASSORY
Insulator - A material or an object that does not easily allow heat,
electricity, light, or sound to pass
through it. Air, cloth and rubber are good electrical
insulators