a) heat and temperature;
b) heat and work:
c) different states of a substance.
Work in pairs. Make up a dialogue.
Unit 6
HEAT A FORM OF ENERGY
1. Memorize the following words and expressions:
Ø convection - a pump -
Ø conduction - ()
Ø combustion chamber -
Ø radiation - ,
Ø a light bulb -
Read the text, study it. Find in the text examples to illustrate the ways heat travel from one object to another.
Heat A Form of Energy
Heat travels from a hot object to a cold object. You might say that heat flows down a temperature hill. So how does heat travel from one object to another? By Conduction, Convection and Radiation.
Liquids and gases do not conduct heat very well, but they can transfer heat by CONVECTION. Look at the engine at the left. Water carries heat from a hot engine through a pump and delivers it to a radiator, whose duty is to give up heat to the air. Remember, with convection, heat is transferred from one place to another by the motion of the gas or liquid. CONDUCTION is the main way for heat to transfer through solid materials. For example, the outside surface of an engine gets hot because heat energy is transferred from the combustion chamber through the metal to the outside surface.
All solid materials conduct heat, but some do a better job than others. Generally, metals are good conductors while porous materials are not. Styrofoam is an example of a poor conductor. It is a great insulator. Good conductors of electricity are usually good conductors of heat.
The easiest way to explain heat transfer by RADIATION is by the heat we feel from the sun. Even though the sun is about 93 million miles away from the earth, we still feel some of its heat. It travels to earth through the vacuum (no air) of space by way of rays! If you hold your hand near a light bulb (but not too close!), much of the heat that you feel is from RADIATION. How else is the light bulb transferring heat to your hand. Would you guess CONVECTION or CONDUCTION?
3. Try to explain the meaning of the given words using the information youve learnt from the text.
1. convection;
2. conduction;
3. radiation.
Solve the crossword puzzle.
Across
1. A pumps heat from one place to another.
2. Heat specific heat capacity x temperature change.
3. This is the time in which the cost of insulating materials is recouped from savings made on energy consumption.
4. 'Hidden' heat.
5. The specific latent heat of of water is the amount of heat required
to change 1 kg of water to steam without a change in temperature.
6. of sweat results in heat loss from the body surface.
7. Capacity is the amount of heat required to change the
temperature of 1kg of a substance by IK (two words - 6)
8. surfaces are the best emitters and absorbers of heat.
|
|
|
9. It is the transfer of energy through a substance without any bodily movement of the substance.
10. - In heaters, a core of high density thermal blocks is heated at night.
11. Theheat is the quantity of energy required to change the
state of 1kg of a substance.
12. It is the transfer of energy by the circulation of a fluid.
Down
1. It is the transfer of energy between two points by means of electromagnetic waves.
2. The specific latent heat ofof ice is the amount of heat required to change 1kg of ice to water without a change in temperature.
3. Water is a conductor.
4. To help a person with a very high temperature, it is more effective to sponge the forehead withwater.
5. Heat lost Heat
6. It is the amount of energy falling normally on unit area of the earth's atmosphere per second when the earth is at its mean distance from the sun
7. Unit heat loss rate.
|
|
|
