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Physics Grade 11 > Unit 3 > Flashcards

Unit 3 Flashcards

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1
Q

What does Stefan-Boltzmann law show?

A

Stephen Boltzmann law shows the relationship between the temperature of a black body and the power emitted by the blackbodies surface area

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2
Q

What does the triple point of water mean

A

The unique temperature and pressure at which water can exist as liquid water, ice and water vapor

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3
Q

What’s is teh internal energy of a substance ?

A

The internal energy of a substance is a total of the potential energy and the random kinetic energy of all the particles in the substance

The sum of the total kinetic energy and the total intermolecular potential energy of the particles within the substance

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4
Q

What is NSE’s trading system called ?

A

NEAT : national exchange for automated trading

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5
Q

What is maximum brokerage prescribed by SEBI ?

A

2.5%

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6
Q

thermal interaction

A

When thermal energy is exchanged, the objects (or systems) involved are said to have a thermal interaction

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7
Q

heat

A

The thermal energy exchanged during a thermal interaction is referred to as heat

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8
Q

Temperature (3)

A

The temperature of an object is a macroscopic measure of the average kinetic energy of the particles (atoms or molecules) that make up the object

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9
Q

Absolute zero(2)

A

Absolute zero is a temperature of zero kelvin (0 K) and corresponds to the temperature at which the average kinetic energy of the molecules is at its minimum

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10
Q

Why does temperature of the substance no change during state change ? 2

A
  1. Since temperature is a measure of the average kinetic energy of the molecules, only an increase in the average kinetic energy of the molecules will result in an increase in temperature of the substance
  2. When only the potential energy of the molecules changes( i.e. the particles get further away from each other or move closer to each other ), the temperature of the substance does not change. This is the case for all state changes (e.g. melting, boiling)
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11
Q

a change in internal energy does not necessarily corresponds to a change in temperature. Explain (2)

A

As thermal energy is transferred to a substance, two things can happen:

An increase in the average kinetic energy of the molecules corresponds to a change in temperature

Or

A change in the average potential energy of the molecules does not affect temperature(change in state)

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12
Q

The amount of thermal energy needed to change the temperature of an object depends on: 3

A

The change in temperature required ΔT - i.e. the larger the change in temperature the more energy is needed

The mass of the object m

The specific heat capacity c of the given substance

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13
Q

specific heat capacity of a substance is defined as:

A

The amount of energy required to change the temperature of 1 kg of a substance by 1 K (or 1°C)

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14
Q

The specific latent heat of a substance is defined as:

A

The amount of energy required to change the state of 1 kg of a substance without changing its temperature

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15
Q

two types of specific heat:

A

Specific latent heat of fusion, Lf
Specific latent heat of vaporisation, Lv

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16
Q

Specific latent heat of fusion is defined as:

A

The energy released when 1 kg of liquid freezes to become solid at constant temperature

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17
Q

Specific latent heat of vaporisation is defined as:

A

The energy released when 1 kg of gas condenses to become liquid at constant temperature

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18
Q

The energy released when 1 kg of gas condenses to become liquid at constant temperature

A
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19
Q

Why is much more energy is needed to evaporate (or condense) a substance than it is needed to melt it (or solidify it) ?

A

In melting, the intermolecular bonds only need to be weakened to turn from a solid to a liquid
When evaporating, the intermolecular bonds need to be completely broken to turn from liquid to gas. This requires a lot more energy.

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20
Q

Is work done by or on teh gas ?

A

The volume decreases, therefore, work is done by the gas (work is also negative in thsi case’

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21
Q

The First Law of Thermodynamics

A

change in internal energy = heat added + work done on the system

Conservation of energy

22
Q

Entropy 3 definitions

A
  1. the measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work
  2. Measure of disorder in a system
  3. The entropy S of a given system is a measure of the number of possible arrangements of the particles and their energies
23
Q

reversible process(macroscopic level)

A

A process where there is no overall change in entropy as the system and its surroundings are returned to their original states

24
Q

Irreversible process(macroscopic level)

A

A process which results in an increase in entropy as the system and its surroundings cannot return to their original states

25
Q

Why does the entropy of a real isolated system always increase ?

A

Processes in real isolated systems are almost always irreversible and consequently, the entropy of a real isolated system always increases

26
Q

isolated system

A

A system in which neither matter nor energy can be transferred in or out

27
Q

entropy of a system two formulas :

A

Macroscopic level : S = Q/T

Microscopic Level : S = k(B) In Ω

28
Q

microstate

A

A microstate describes the number of states or possible arrangements of the particles in the system

29
Q

Ω

A

Ω = the number of possible microstates of the system

30
Q

What do microstates help do ?

A

microstates as a way of quantifying the certainty of information we have about the system

Eg! A solid has lower entropy than a gas because we can be more certain about the location of the atoms in the solid

31
Q

Second Law of Thermodynamics

A

In every process, the total entropy of an isolated system always increases

32
Q

Clausius form of the second law states:

A

Thermal energy cannot spontaneously transfer from a region of lower temperature to a region of higher temperature

33
Q

Why is the word spontaneous improtant in the Clausius form of teh second law ?

A

The use of the word ‘spontaneously’ is the key here, as heat pumps are an example of a way that heat can be transferred from a colder region to a hotter one by doing work

34
Q

the Kelvin form of the second law

A

When extracting energy from a heat reservoir, it is impossible to convert it all into work

35
Q

The four main thermodynamic processes are

A

Isovolumetric
Isobaric
Isothermal
Adiabatic

36
Q

An isobaric process is defined as:

A

A process in which no change in pressure occurs

37
Q

An isovolumetric process is defined as:

A

A process where no change in volume occurs and the system does no work

38
Q

adiabatic

A

A process where no heat is transferred into or out of the system

39
Q

heat engine

A

A heat engine is a device that converts thermal energy into mechanical work

40
Q

closed cycle

A

A closed cycle is one in which the system returns to its initial state

41
Q

Carnot cycle

A

A thermodynamic system that runs at its greatest possible efficiency follows a cycle called the Carnot cycle

42
Q

The total power P radiated by a perfect black body depends on two factors:

A

It’s absolute temperature
It’s surface area

43
Q

Conduction

A

Which is the transfer of thermal energy via intramolecular collisions

44
Q

Convection

A

Which is the transfer of thermal energy via bulk movement of a fluid due to a change of density

45
Q

Radiation

A

Which is the transfer of thermal energy via electromagnetic waves (or words to that effect)

46
Q

Wavelength, frequency and energy correlation

A

As wavelength decreases, frequency increases and energy increases

47
Q

Wavelengths and temprature

A

Lower wavelength corresponds to higher temperatures

48
Q

Wien’s law

A

λmax = b / T

where: λmax is the wavelength at peak radiation intensity in meters. b is Wien’s constant in meter-kelvin. T is the absolute temperature in kelvin.

0.0029

49
Q

Emissivity

A

The power radiated by a surface divided by the power radiated from a black body of the same surface area and temperature

50
Q

Perfect black body

A

An object that absorbs all of the radiation incident on it and does not reflect or transmit any radiation

51
Q

Emissivity

A

The power radiated by a surface divided by the power radiated from a black body of the same surface area and temperature

Physics Grade 11 (4 decks)

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