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CGIER > Lecture 17 > Flashcards

Lecture 17 Flashcards

1
Q

What is a system?

A

That part of the universe we are studying

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2
Q

What are surroundings?

A
  • The parts of the surroundings that interact with the system
  • The rest of the universe
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3
Q

What are interactions?

A

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

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4
Q

What are the 3 different types of systems?

A

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

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5
Q

An open system?

A

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

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6
Q

A closed system?

A

Can exchange energy but not matter with its surroundings

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7
Q

An isolated system?

A

Exchanges neither matter or energy with its surroundings

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8
Q

What is internal energy (U)?

A

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

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9
Q

What are the means by which a system exchanges energy?

A

Heat and work

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10
Q

When does heat and work only exist?

A

During a change in the system

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11
Q

What is the formula for internal energy?

A

ΔU = q + w

Internal energy = heat + work

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12
Q

What is heat?

A
  • 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
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13
Q

Which direction does heat transfer?

A

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

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14
Q

Thermal equilibrium?

A

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

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15
Q

What temperature a measure of?

A

The average translational kinetic energy of molecules in a sample

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16
Q

Work?

A

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

Work = Force x distance

17
Q

First law of Thermodynamics?

A

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

18
Q

Different types of internal energy?

A
  • Translational kinetic energy
  • Molecular rotation
  • Bond vibration
  • Intermolecular attractions
  • Energy in Chemical bonds
  • Energy associated with electrons in atoms
19
Q

Exothermic reactions?

A
  • Chemical energy in a system is converted to thermal energy
  • Heat is released to surroundings
  • Bonds are formed
  • Enthalpy is negative (-deltaH)
  • Ex. combustion
20
Q

Endothermic reactions?

A
  • Thermal energy in a system is converted to chemical energy
  • Heat is absorbed from surroundings
  • Bonds are broken
  • Enthalpy is positive (+deltaH)
  • Ex. photosynthesis
21
Q

What are the food energy sources?

A
  • Fats (lipids)
  • Proteins
  • Carbohydrates (sugars)
  • Alcohols
22
Q

What is the role of food energy?

A

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

23
Q

How do we find the energy content of food?

A

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

24
Q

What does Hess’s Law state?

A

The heat of a reaction is independent of the route taken

25
Q

Caloeimetry?

A

The measure of heat changes

26
Q

What is specific heat capacity?

A

The amount of heat required to raise the temperature of 1g

of substance by 1 degree C

27
Q

What is heat capacity?

A

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
28
Q

What is the S.H.C of water?

A
  1. 0 cal/g C

- This is the standard value

29
Q

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

A

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)

30
Q

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

A
  1. Mass of substance
  2. Temperature of change required
  3. Its S.H.C.
31
Q

What are the three principle components of energy expenditure?

A
  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
32
Q

Basal Metabolic Rate (BMR)?

A

The rate at which chemical energy is used for basal activities

33
Q

What does BMR depend on?

A
  • the person (gender etc)
  • their activity
  • their weight

CGIER (16 decks)

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