Physics Thermal energy Flashcards
Thermal Energy
What is thermal equilibrium?
A state in which there is no net flow of thermal energy between two or more bodies in thermal contact, implying they are at the same temperature.
What does it mean for two objects to be in thermal contact?
They can exchange thermal energy with each other, typically through conduction, convection, or radiation.
What is the direction of net thermal energy flow between two bodies?
Thermal energy flows from a region of higher temperature to a region of lower temperature.
What is the Zeroth Law of Thermodynamics?
If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other.
What does reaching thermal equilibrium indicate about temperature?
If two bodies have the same temperature, they are in thermal equilibrium, and no net heat transfer will occur.
How does thermal equilibrium appear at the microscopic level?
The molecules within each body are in motion and exchanging energy, but the average energy remains constant.
What is a temperature scale?
A system for assigning numerical values to different degrees of hotness or coldness based on fixed reference points.
What are fixed points in a temperature scale?
Precisely reproducible temperatures used to define a temperature scale, such as the ice point and steam point.
Define the Celsius scale (°C).
Defined using the ice point as 0 °C and the steam point as 100 °C, divided into 100 equal divisions.
What is the Kelvin scale (K)?
The absolute temperature scale based on absolute zero, defined as 0 K.
What is the relationship between Celsius and Kelvin?
T(K) = T(°C) + 273.15.
What is the specific heat capacity (c)?
The amount of thermal energy required to raise the temperature of one kilogram of a substance by one Kelvin.
What is the formula for calculating heat energy transferred?
Q = mcΔT.
What does a high specific heat capacity indicate?
A substance requires a large amount of thermal energy to produce a small temperature change.
What is the specific latent heat (L)?
The amount of thermal energy required to change the state of one kilogram of a substance without any change in temperature.
What is the specific latent heat of fusion (Lf)?
The thermal energy required to change one kilogram of a substance from solid to liquid at its melting point.
What is the specific latent heat of vaporization (Lv)?
The thermal energy required to change one kilogram of a substance from liquid to gas at its boiling point.
What does the First Law of Thermodynamics state?
The change in internal energy of a system is equal to the net heat added minus the net work done by the system.
What is internal energy (U)?
The total energy stored within a system, including kinetic and potential energy of all particles.
What is entropy (S)?
A measure of the disorder or randomness of a system.
What does the Second Law of Thermodynamics state?
The total entropy of an isolated system can only increase or remain constant; it never decreases.
What is the significance of the First Law of Thermodynamics?
It is a statement of conservation of energy, indicating energy cannot be created or destroyed.
What is the mathematical formulation of the First Law of Thermodynamics?
ΔU = Q - W.
What happens during a phase change regarding temperature?
The temperature remains constant while thermal energy is absorbed or released.
Fill in the blank: The specific latent heat of fusion of ice at 0 °C is approximately _______.
3.34 × 10⁵ J kg⁻¹
Fill in the blank: The specific latent heat of vaporization of water at 100 °C is approximately _______.
2.26 × 10⁶ J kg⁻¹
True or False: The specific heat capacity of a substance is the same at all temperatures.
False
What is the relationship between heat and work in the context of the First Law of Thermodynamics?
Heat added to the system is positive and work done by the system is positive.
What does a state function mean in the context of internal energy?
The change in internal energy (ΔU) depends only on the initial and final states of the system, not on the path taken to get there.
What is often difficult to determine regarding the internal energy of a system?
The absolute value of the internal energy.
What is usually of concern when discussing internal energy?
The change in internal energy (ΔU), which can be measured or calculated.
For an ideal monatomic gas, what is the internal energy solely due to?
The translational kinetic energy of its atoms.
What is the relationship between internal energy and absolute temperature for an ideal monatomic gas?
Internal energy (U) is directly proportional to the absolute temperature.
What is the equation for internal energy (U) of an ideal monatomic gas?
U = (3/2)nRT, where n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.
Fill in the blank: The change in internal energy (ΔU) is a _______.
state function
True or False: The internal energy of a system can be directly measured.
False
Fill in the blank: The internal energy of an ideal monatomic gas is proportional to the absolute temperature, represented as U = _______.
(3/2)nRT
