CGIER 17 - Food, Energy, And Calorimetry

Question 1

What is Thermodynamics?

Answer 1

Thermodynamics is the science that deals with the relationship between heat and work.

Question 2

What is Thermochemistry?

Answer 2

Thermochemistry is the study of the energy changes that occur during physical and chemical reactions.

Question 3

Explain what is meant by a system, surroundings, and interactions.

Answer 3

A system is the part of the universe in which the reaction takes place, while surroundings are the rest of the universe that interacts with the system. Interactions refer to the exchange of energy between the system and the surroundings.

Question 4

List and explain the three types of systems.

Answer 4

There are three types of systems:

1. Open system: can exchange matter and energy with its surroundings
2. Closed system: can exchange energy, but not matter with its surroundings.
3. Isolated system: cannot exchange energy or matter with its surroundings.

Question 5

What is Internal Energy?

Answer 5

Internal energy is the total energy contained within a system, either as kinetic or potential energy.

Question 6

How does a system exchange energy?

Answer 6

A system exchanges energy through heat and work.

Question 7

What is heat?

Answer 7

Heat is a quantity of energy transferred between a system and its surroundings as a result of a temperature difference between them. Heat always transfers from a region of higher temperature to a lower temperature until both regions reach thermal equilibrium.

Question 8

What is the difference between heat and temperature?

Answer 8

Heat is a quantity of energy, while the temperature is a measure of the average kinetic energy of the molecules of a sample.

Question 9

What is work?

Answer 9

Like heat, it is an energy transfer between a system and its surroundings, but a system does not contain work.

Question 10

State the First Law of Thermodynamics.

Answer 10

Energy cannot be created nor destroyed, it can only be converted from one form to another.

Question 11

What is the difference between an exothermic reaction and an endothermic reaction?

Answer 11

An exothermic reaction releases heat into its surroundings during product formation (combustion reactions are always exothermic), while an endothermic reaction absorbs heat from its surroundings for product formation.

Question 12

How is energy measured in nutrition?

Answer 12

Energy is measured in joules or calories:

1 kcal = 1000 cal = 4184 J

Question 13

What is the difference between a combustion reaction and a metabolism reaction?

Answer 13

A combustion reaction is a high-temperature process that takes place in one step (products are always carbon dioxide and water), while metabolism takes place at 37 degrees and it a multi-step process. You can measure the heat released from combustion, but not metabolism.

Question 14

What is Hess’s Law?

Answer 14

Hess’s Law states that the heat of a reaction is independent of the route taken. In other words, this means that the amount of heat produced does not depend on the number of steps of the reaction.

Question 15

What is Calorimetry?

Answer 15

Calorimetry is the measure of heat changes.

Question 16

What is specific heat capacity?

Answer 16

Specific heat capacity is the amount of heat required to raise the temperature of 1g of a substance by 1 degrees Celsius. The specific heat capacity of water is 1 cal/g x 1 degree Celsius.

Question 17

What is heat capacity?

Answer 17

The amount of heat required to raise the temperature of a given quantity of a substance by 1 degree Celsius.

Question 18

How does a bomb calorimeter work?

Answer 18

A known mass of a food sample is placed in an inner chamber that is filled with O2. The closed bomb is immersed in a known amount of water and sample is ignited electrically. A combustion reaction takes place and the energy released heats the surrounding water, and the rise in temperature, indicated by the thermometer, can be used to calculate the number of calories emitted.

Question 19

What are three ways you can expend energy?

Answer 19

1. Basal Metabolic Rate: responsible for 60-70% of energy expenditure, energy expended during resting state.
2. Physical Activity
3. Thermic Effect: the metabolism of food, responsible for 10% of energy expenditure

Question 20

Define basal activities.

Answer 20

Activities in the body that must take place for you to survive. (Circulation, respiration, temperature maintenance, nerve transmission, kidney function)

Question 21

What is a nutritional requirement?

Answer 21

Nutritional requirement is the amount of a specific nutrient required to prevent clinical signs of deficiency.