3. Complete the sentences.

1. Heat may be defined as. ..

2. The internal energy may be increased by...

3. If you are presented with a high temperature gas, you cannot tell...

4. The word heat is better reserved...

5. The First Law identifies both heat and work as...

4. Write down as many questions to the given sentences as possible.

1. In a classic experiment in 1843, James Joule showed the energy equivalence of heating and doing work by using the change in potential energy of falling masses to stir an insulated container of water with paddles.

2. Heat flow and work are both ways of transferring energy.

3. The temperature of a gas can be raised either by heating it, by doing work on it, or a combination of the two.

5. Say if the statements are true or false;

1. Work may be defined as energy in transit from a high temperature object to a lower temperature object.

2. The appropriate term for the microscopic energy in an object is external energy.

3. It is better to say that a high temperature object possesses internal energy as a result of its molecular motion.

4. The internal energy may be increased by transferring energy to the object from a higher temperature (hotter) object.

5. You can take an object at low internal energy and raise it to higher internal energy by heating it.

6. Answer the questions.

1. How may be heat defined?

2. 2 How is heating properly called?

3. Can we tell whether gas reached that high temperature by being heated or by having work done on it. or a combination of the two?

4. What is better to say: an object "possesses heat" or "possesses internal energy"? Why?

5. W hat experiment was done in 1843?

6. What does the first Law of Thermodynamics indicate?

7. You are trying to explain your pat iner the difference between;

1. heat and temperature;

2. Heat and work:

3. different states of a substance.

8. Work in pairs. Make up a dialogue.

Unit 6

HEAT A FORM OF ENERGY

1. Memorize the following words and expressions:

• convection - конвекція a pump - насос

• conduction - (електро) провідність

• combustion chamber - камера згорання

• radiation - випромінювання, радіація

• a light bulb - електрична лампочка

2. 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?