# More About Heat. Heat is energy

Heat is the total amount of energy possessed by the molecules in a piece of matter. This energy is both kinetic energy and potential energy. When heat, (i.e., energy), goes into a substance one of two things can happen:

1.The substance can experience a raise in temperature. That is, the heat can be used to speed up the molecules of the substance. Since Kelvin temperature is directly proportional to the average kinetic energy of molecules in a substance, and factor increase in temperature causes an equal factor increase in the average kinetic energy of the molecules. And if the kinetic energy of the molecules increases, the speed of the molecules will increase, although these increases are not directly proportional. The kinetic energy of a body is proportional to the square of the speed of the body.

2.The substance can change state. For example, if the substance is ice, it can melt into water. Perhaps surprisingly, this change does not cause a raise in temperature. The moment before melting the average kinetic energy of the ice molecules is the same as the average kinetic energy of the water molecules a moment after melting. Although heat is absorbed by this change of state, the absorbed energy is not used to speed up the molecules. The energy is used to change the bonding between the molecules. Changing the manner in which the molecules bond to one another constitutes a change in potential energy. Heat comes in and there is an increase in the potential energy of the molecules. Their kinetic energy remains unchanged. So, when heat comes into a substance, energy comes into a substance. That energy can be used to increase the kinetic energy of the molecules, which would cause an increase in temperature. Or that heat could be used to increase the potential energy of the molecules causing a change in state that is not accompanied-by an increase in temperature.

Put the sentences in the correct order according to the text.

1. The substance can experience a raise in temperature.

2. Temperature can be measured in a variety of units.

3. Heat comes in and there is an increase in the potential energy of the molecules.

4. The substance can change state.

5. The energy is used to change the bonding between the molecules.

6. Temperature directly relates to the kinetic energy of the molecules.

7. Temperature is a number that is related to the average kinetic energy of the molecules of a substance.

1. When you heat something up, then the temperature of that something .

a) goes down;

b) goes up;

c) remains the same.

2. Temperature is a number that is related to the average energy of

the molecules of a substance.

a) potential;

b) total;

c) kinetic.

3. Heat is a measurement of the energy in a substance,

a) potential;

b) total;

c) kinetic.

4. When heat goes into a substance,

a) the substance can experience a raise in temperature;

b) the substance changes state;

c) nothing happens.

5. When heat comes into a substance, energy a substance.

a) comes out;

b) comes into;

c) remains the same.

1. What is temperature?

2. What can we measure it in?

3. What is the difference between heat and temperature? Are they the same?

4. Why are they not the same?

6. Complete the dialogue and perform it in pairs.

— What do you know about the difference between heat and temperature?

— Are they the same?

— What is temperature?

— How can it be measured?

— What is heat?

— What happens when heat comes into a substance?

7. Now try to tell the gist of the text in 15 sentences. Use the questions from Ex. 6 to help you.

Unit З.

UNIT OF HEAT. TEMPERATURE

1. Memorize the following words and expressions: plasma - плазма

Ø to undergo - підлягати чомусь, зазнавати чогось

Ø content - склад

Ø a bond - зв’язок

Ø rigid - твердий

Ø melting - розставання, танення

Ø back and forth - назад і вперед