The energy required to change the state of a substance without changing its temperature is governed by which quantity?
Specific latent heat
Specific heat capacity
Thermal conductivity
Internal pressure
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Why$Q=mL$, where $L$ is the specific latent heat. During a change of state the temperature is constant.
4Multiple choice · Easy
Heat transfer through a metal rod by direct vibration of particles, without bulk movement of the material, is called:
Conduction
Convection
Radiation
Evaporation
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WhyConduction transfers energy through particle vibrations and free electrons without net movement of the material.
5Multiple choice · Medium
The internal energy of an ideal gas is best described as:
The total random kinetic energy of its molecules
The work done on the gas
The heat supplied to the gas
The ordered kinetic energy of the gas as a whole
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WhyInternal energy is the total of the random kinetic (and, in real substances, potential) energies of the molecules. For an ideal gas it is purely molecular kinetic energy.
6Multiple choice · Hard
A hot $0.10\,\text{kg}$ block is dropped into water. At thermal equilibrium, what is true of the block and water temperatures?
They are equal
The block is still hotter
The water is hotter
They differ by the latent heat
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WhyAt thermal equilibrium there is no net energy flow, which requires the two temperatures to be equal.
7Fill in the blank · Easy
The energy needed to change the state of $1\,\text{kg}$ of a substance at constant temperature is its specific latent .
Answer:
heat
Why$Q=mL$; the specific latent heat is the energy per kilogram for the phase change (fusion or vaporisation).
8Fill in the blank · Medium
Absolute zero, the lowest possible temperature, is approximately $^{\circ}\text{C}$.
Answer:
-273 / -273.15
WhyAbsolute zero is $0\,\text{K}=-273\,^{\circ}\text{C}$ (more precisely $-273.15\,^{\circ}\text{C}$).
9Multiple choice · Medium
A mass m of a substance with specific heat capacity c is heated through a temperature change of delta T. The energy supplied is given by which expression?
Q = m c delta T
Q = m c / delta T
Q = c delta T / m
Q = m delta T / c
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WhyQ = m c delta T relates energy to mass, specific heat capacity and temperature change.
10Multiple choice · Hard
2.60 x 10^-8 kg of air (specific heat capacity 1010 J/kg degrees C) absorbs 0.0130 J. What is its temperature change?
495 degrees C
49.5 degrees C
4950 degrees C
0.0202 degrees C
Tap an answer to check it.
Whydelta T = Q / (m c) = 0.0130 / (2.60e-8 x 1010) = 495 degrees C.
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