Lecture 17

Question 1

What is a system?

Answer 1

That part of the universe we are studying

Question 2

What are surroundings?

Answer 2

• The parts of the surroundings that interact with the system
• The rest of the universe

Question 3

What are interactions?

Answer 3

Is the exchange of energy or matter between a system and surroundings

Question 4

What are the 3 different types of systems?

Answer 4

An open system, a closed system, and an isolated system

Question 5

An open system?

Answer 5

Can exchange either matter or energy (or both) with its surroundings

Question 6

A closed system?

Answer 6

Can exchange energy but not matter with its surroundings

Question 7

An isolated system?

Answer 7

Exchanges neither matter or energy with its surroundings

Question 8

What is internal energy (U)?

Answer 8

The total energy contained within a system, partly as kinetic energy and partly as potential energy

Question 9

What are the means by which a system exchanges energy?

Answer 9

Heat and work

Question 10

When does heat and work only exist?

Answer 10

During a change in the system

Question 11

What is the formula for internal energy?

Answer 11

ΔU = q + w

Internal energy = heat + work

Question 12

What is heat?

Answer 12

• A quantity of energy transferred between a system and its surroundings as a result of a temperature difference between them
• Heat is a transfer of molecular kinetic energy that brings a system and its surroundings to the same temperature

Question 13

Which direction does heat transfer?

Answer 13

Passes spontaneously from the region of higher temperature to the region of lower temperature

Question 14

Thermal equilibrium?

Answer 14

When the heat transfer stops when the surroundings reach the same temp

Question 15

What temperature a measure of?

Answer 15

The average translational kinetic energy of molecules in a sample

Question 16

Work?

Answer 16

Is an energy transfer between a system and its surroundings, a system does not contain work

Work = Force x distance

Question 17

First law of Thermodynamics?

Answer 17

In a physical or chemical change, energy can be exchanged between a system and its surroundings but energy cannot be created nor destroyed, it can only be converted from one form to another

Question 18

Different types of internal energy?

Answer 18

• Translational kinetic energy
• Molecular rotation
• Bond vibration
• Intermolecular attractions
• Energy in Chemical bonds
• Energy associated with electrons in atoms

Question 19

Exothermic reactions?

Answer 19

• Chemical energy in a system is converted to thermal energy
• Heat is released to surroundings
• Bonds are formed
• Enthalpy is negative (-deltaH)
• Ex. combustion

Question 20

Endothermic reactions?

Answer 20

• Thermal energy in a system is converted to chemical energy
• Heat is absorbed from surroundings
• Bonds are broken
• Enthalpy is positive (+deltaH)
• Ex. photosynthesis

Question 21

What are the food energy sources?

Answer 21

• Fats (lipids)
• Proteins
• Carbohydrates (sugars)
• Alcohols

Question 22

What is the role of food energy?

Answer 22

For energy to be released from the food for things like circulation, kidney function, nerve transmission, etc

Question 23

How do we find the energy content of food?

Answer 23

We can measure the heat released from combustion, and then correlate that to metabolism in the body

Question 24

What does Hess’s Law state?

Answer 24

The heat of a reaction is independent of the route taken

Question 25

Caloeimetry?

Answer 25

The measure of heat changes

Question 26

What is specific heat capacity?

Answer 26

The amount of heat required to raise the temperature of 1g | of substance by 1 degree C

Question 27

What is heat capacity?

Answer 27

Amount of energy required to raise the temperature of a given quantity of substance by 1oC Heat capacity = mass(g) x specific heat capacity(cal/g C) - Only difference between this and S.H.C is that we're investigating a particular mass

Question 28

What is the S.H.C of water?

Answer 28

1. 0 cal/g C | - This is the standard value

Question 29

Why is water's specific heat capacity so important to us?

Answer 29

Bc water makes up 60% of our body, so water having the highest S.H.C means that our bodies have a thermal cushion (we can withstand large swings in environmental temperature)

Question 30

What does the energy required to change the temperature of a substance depend on?

Answer 30

1. Mass of substance 2. Temperature of change required 3. Its S.H.C.

Question 31

What are the three principle components of energy expenditure?

Answer 31

1. Basal metabolic rate – the energy expended by the body in a state of rest - 60-70% of daily energy expenditure. (ex. circulation, respiration, kidney function, etc) 2. Thermic effect represents the stimulation of metabolism due to the processing of food and storage of macronutrients – c. 10% of daily energy expenditure. 3. Physical activity- energy expended during any type of physical exercise

Question 32

Basal Metabolic Rate (BMR)?

Answer 32

The rate at which chemical energy is used for basal activities

Question 33

What does BMR depend on?

Answer 33

- the person (gender etc) - their activity - their weight