thermal stuff Flashcards

1
Q

what is internal energy

A

sum of random kinetic and potential energy of all molecules in a system

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2
Q

explain how internal energy of a gas is different from that of liquid

A

higher temp so higher KE; higher PE due to latent heat

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3
Q

explain why gas pressure increases with temperature; use the kinetic theory of gases

A

higher temp means higher speed of molecules; this means more frequent collisions; also larger change in momentum with each collision

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4
Q

describe an electrical experiment to find specific heat capacity of a sample of oil; use a labelled diagram

A

see book

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5
Q

explain what happens to the temperature of a substance as it changes phase

A

temperature stays constant; energy taken in is converted to potential energy (latent heat)

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6
Q

what are the assumptions made in the ideal gas model

A

collision with container is elastic; force between molecules is zero except in collisions; volume of molecules negligible compared to container; time of collisions negligible compared to time between collisions

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7
Q

explain gas pressure in terms of newton’s laws of motion and the ideal gas model

A

momentum of molecule changes when colliding with wall; change in momentum over time = force on molecule; force on molecule equal and opposite to force on wall; sum of forces on wall / area = pressure

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8
Q

a gas molecule hits a wall with speed v and momentum mv; explain why it rebounds with speed v and gets an impulse of 2mv

A

collision is elastic so velocity becomes -v; change in momentum = mv - (-mv) = 2mv

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9
Q

what is boyle’s law

A

for a fixed mass of gas at constant temp; pressure x volume = constant

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10
Q

what is specific heat capacity

A

energy required to raise temperature of 1kg of a material by 1K

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11
Q

what is absolute zero

A

lowest limit for temperature; minimum internal energy

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12
Q

why does a body’s internal energy increase as its temperature increases

A

its molecules gain higher KE; internal energy is sum of KE and PE

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13
Q

how is absolute zero estimated using a graph of temperature and pressure

A

gradient from line of best fit is used; temperature extrapolated for when pressure becomes 0

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14
Q

what is the root mean square of a set of numbers

A

square root of the mean of the squares of each number

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15
Q

how to calculate the boltzmann constant

A

molar gas constant (R) / avogadro constant (NA)

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16
Q

what is specific latent heat of fusion

A

energy to convert 1kg of substance at melting point from solid to liquid

17
Q

a block of paraffin wax melts at a constant temperature of 52 degrees; explain the change in its internal energy

A

temp stays constant => KE stays the same; melting => PE increase due to latent heat of fusion; internal energy increase