Question

Which of the following statements is true?

•Temperature is an average measure of the heat energy in a substance.
•The transfer of heat in a fluid does not require physical contact between molecules.
•The sun's energy comes from the nuclear reactions of changing hydrogen into helium.
•All of the above.

Answer 1

Explanation:

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Answer 2

All of the given statements are true.

First statement

Temperature is an average measure of the heat energy in a substance.

• Temperature is the hotness or coldness of a body.
• When the temperature of a body is increased, the substance gets heated. As a result, the molecules start to vibrate rapidly.

Hence, the temperature is also called the average kinetic energy of the molecules of a body.

Second statement

The transfer of heat in a fluid does not require physical contact between molecules.

• Convection is a process by which heat gets transferred through the motion of molecules of fluids themselves.
• Heat always gets transferred from a hot body to a cold body.

Hence, the transfer of heat in a fluid takes place due to differences in the density of hot molecules and cold molecules.

Third statement

The sun's energy comes from the nuclear reactions of changing hydrogen into helium.

• The energy from the sun is due to the thermonuclear fusion reaction occurring in the sun.
• Hydrogen atoms combine to form Helium with the release of a tremendous amount of heat energy.

Thus, the energy produced during nuclear fusion reaction in sun is radiated to the earth.