Reaction Rates and Thermodynamics

Question 1

A hot cup of coffee placed upon the kitchen table will cool down. Which law of thermodynamics does this illustrate?

A. The zeroth law
B. The first law
C. The second law
D. The third law
E. The combined law

Answer 1

A. A hot cup of coffee cools until its temperature reaches that of its surroundings, in other words, until it reaches thermal equilibrium with its surroundings. This illustrates the zeroth law of thermodynamics.

Question 2

What happens to the temperature of a gas which is allowed to expand adiabatically?

A. The temperature decreases
B. The temperature increases
C. The temperature remains constant

Answer 2

A. A gas allowed to rapidly expand adiabatically will tend to cool. This is put to use in the cryoprobe and is an illustration of the first law of thermodynamics.

A gas rapidly compressed adiabatically will tend to heat. This may cause a risk of explosion when it occurs within anaesthetic pipelines and gauges contaminated with oil or grease.

Question 3

Which law of thermodynamics does the following statement relate to?

Entropy tends to increase over time

Answer 3

Second law

Question 4

Which law of thermodynamics does the following statement relate to?

Energy can neither be created nor destroyed

Answer 4

First law

Question 5

Which law of thermodynamics does the following statement relate to?

This law allows you to create a thermometer

Answer 5

Zeroth law

Question 6

Which law of thermodynamics does the following statement relate to?

This relates the entropy of matter to its absolute temperature

Answer 6

Third law

Question 7

The following statement illustrates the first law of thermodynamics (true or false):

The continuous swinging of a pendulum

Answer 7

True. As a pendulum swings, energy is repeatedly converted from kinetic energy to gravitational potential energy (and vice versa). The total energy within the system remains constant.

Question 8

The following statement illustrates the first law of thermodynamics (true or false):

The cooling of a hot cup of coffee on the kitchen table

Answer 8

False. The flow of heat energy from a hotter object to a cooler one illustrates the zeroth law of thermodynamics.

Question 9

The following statement illustrates the first law of thermodynamics (true or false):

The measurement of body temperature by a mercury thermometer

Answer 9

False. This relies on the flow of heat from the body into the cooler thermometer, resulting in an expansion of the mercury until the two bodies are in thermal equilibrium. This flow of heat energy illustrates the zeroth law of thermodynamics.

Question 10

The following statement illustrates the first law of thermodynamics (true or false):

Cooling of a gas by adiabatic expansion

Answer 10

True. A gas allowed to expand adiabatically requires energy to break down the van der Waals forces between the molecules. This energy is taken from the kinetic energy of the molecules themselves, resulting in a fall in temperature of the gas.

Question 11

The following statement illustrates the first law of thermodynamics (true or false):

The entrainment of air by a nebulizer

Answer 11

True. This relies on the Venturi effect.