Heat and Temperature

Question 1

Regarding heat loss (true or false):

Conduction is the largest factor in patient heat loss

Answer 1

False. Patient heat loss is mainly due to radiation (40%) and, to a lesser extent, convection and evaporation.

Question 2

Regarding heat loss (true or false):

Convection is due to heating of the adjacent air layer, which is replaced by cooler air from the surroundings

Answer 2

True

Question 3

Regarding heat loss (true or false):

Radiation accounts for about 20% of the body’s total heat loss in theatre

Answer 3

False. Losses by radiation typically account for at least 40% of the total heat loss from the body in theatre.

Question 4

Regarding heat loss (true or false):

Heat lost in breathing dry gases is approximately 10% of total heat loss in the anaesthetized patient

Answer 4

True. About 10% of heat loss in the anaesthetized patient is via the respiratory tract. The main part of this is due to the latent heat needed to vaporize water to humidify the gas within the trachea.

Question 5

Regarding heat loss (true or false):

The Stefan-Boltzmann law relates the radiated heat loss from an object to its temperature

Answer 5

True

Question 6

Regarding heat and temperature (true or false):

Heat is a form of energy

Answer 6

True

Question 7

Regarding heat and temperature (true or false):

When measured in Kelvin, temperature is inversely proportional to the average kinetic energy of the molecules of a substance

Answer 7

False. Temperature in Kelvin is directly proportional to the average kinetic energy of the molecules of a substance.

Question 8

Regarding heat and temperature (true or false):

Heat is always transferred from objects with a higher total heat energy to those with a lower total heat energy

Answer 8

False. Heat is transferred from an object with a higher temperature to an object with a lower temperature, regardless of the overall heat energy possessed by each object.

Question 9

Regarding heat and temperature (true or false):

Heat energy of a substance depends upon the mass of the substance

Answer 9

True. Heat energy is a measure of the total energy of molecular motion in a substance and, therefore, is dependent on the mass of the substance.

Question 10

Regarding heat and temperature (true or false):

In the human body, enzymatic activity increases in proportion to increasing temperature

Answer 10

False. Enzymatic activity increases with increasing temperature but when the temperature increases above an optimum temperature, enzymatic activity falls.

Question 11

Regarding heat and heat capacity (true or false):

The units of specific heat capacity are kJ/kg/K

Answer 11

True

Question 11

Regarding heat and heat capacity (true or false):

Specific heat capacity is defined as the amount of heat energy required to raise the temperature of a given object by 1 K

Answer 11

False. This is the definition of heat capacity. Specific heat capacity is mass dependent.

Question 12

Regarding heat and heat capacity (true or false):

During a transfusion of blood at room temperature, the amount of heat energy taken up by the blood is equal to that lost by the body

Answer 12

True. The overall energy must remain the same. Heat is transferred from the object with the higher temperature, i.e. the body, to that with the lower temperature, i.e. the blood.

Question 13

Regarding heat and heat capacity (true or false):

The specific heat capacity governs the change in energy when a substance changes state from liquid to gas

Answer 13

False. This is the latent heat of vaporization.

Question 14

Regarding heat and heat capacity (true or false):

A change in temperature of 1°C is equal to a change in temperature of 1 K

Answer 14

True. However, temperature in Kelvin is 273 degrees higher than temperature measured in Celsius.