3. 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.

4. Choose the correct answer.

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

1. goes down;

2. goes up;

3. remains the same.

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

the molecules of a substance.

1. potential;

2. total;

3. kinetic.

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

1. potential;

2. total;

3. kinetic.

4. When heat goes into a substance,

1. the substance can experience a raise in temperature;

2. the substance changes state;

3. nothing happens.

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

1. comes out;

2. comes into;

3. remains the same.

5. Answer the following questions.

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?

5. 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?

5. 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

• to undergo - підлягати чомусь, зазнавати чогось

• content - склад

• a bond - зв’язок

• rigid - твердий

• melting - розставання, танення

• back and forth - назад і вперед

2. Read the text, study it. Find in the text examples to illustrate different states of a substance.

Changes of Phase (or State)

The term 'change of phase' means the same thing as the term 'change of state'.

There are four states, or phases, of matter. They are: Solid, Liquid, Gas, Plasma.

When a substance changes from one state, or phase, of matter to another we say that it has undergone a change of state, or we say that it has undergone a

change of phase. These changes of phase always occur with a change of heat. Heat, which is energy, either comes into the material during a change of phase or heat comes out of the material during this change. However, although the heat content of the material changes, the temperature does not. So, how could there be a change in heat during a phase change without a change in

temperature? Remember that heat is energy, and remember that there; are two types of energy - kinetic and potential. The heat exchanges, or energy exchanges present during a change in phase are changes in potential enemy, these energy exchanges are not changes in kinetic energy.

If heat is coming into a substance during a phase change, then this energy 'is used to break -the bonds between the molecules of the substance. The example we will use here is ice melting into water. After the molecular bonds in the ice are broken the molecule:» are at a higher potential energy state, however they are not on the average moving any faster, so their average kinetic energy remains the same, and thus, their Kelvin temperature remains the same. In the ice the molecules are strongly bonded to one another, thus forming a rigid solid. When heat is added to the ice, these bonds are broken and the molecules, now at a higher potential energy state, bond to one another with less strength. Water is formed. Now, before the melting the molecules were actually moving when in the solid state. They were vibrating back and forth. So, they had an average speed, and thus, an average kinetic energy. So, they had a Kelvin temperature proportional to this average kinetic energy. After the melting the water molecules are moving, also. And they have the same average speed and the same average kinetic energy as they had before the melting So, the water is at the same temperature the moment after the melting that the ice was at the moment before the melting. Heat came into the situation, but it was not used to change the speed of the molecules. It was used to change the bonding between the molecules. To break the bonds between the molecules of the ice required energy, and this is was the use for the heat. The average speed of the molecules is the same before and after a phase

change, so, the average kinetic energy is the same. And thus, again, we state that the temperature does not change during a change in phase.