Chapter 3 - Thermal Physics Flashcards
What direction does thermal energy naturally flow in?
Flows from hot to cold.
The temperature difference between two objects in thermal contact will determine the direction of the thermal energy transfer.
What is thermal equilibrium?
When two objects are placed in thermal contact they are expected to reach the same temperature.
How to convert between Kelvins and Celsius, and what zero Kelvin means
T (K) = t (Celsius) + 273
Zero Kelvin is absolute zero where particles have no energy left. However this is impossible in reality because the particles would have to be in a vacuum.
What is pressure in terms of gases, the equation and the units.
Pressure is the force per unit area from the gas acting 90 degrees on the container wall.
p = F/A
A = surface area
Units: Nm^-2 or Pa
How to investigate how quantities are interrelated.
One quantity to be the independent variable, one to be the dependant and another to be the control
Macroscopic point of view
Considers the system as a whole and how it interacts with the surroundings.
Microscopic point of view
Looks inside the system on how the components interact with each other.
How the particles act in terms of the kinetic theory and kinetic energy.
The particles are constantly in random motion and therefore have kinetic energy.
They can have translational kinetic energy ( whole molecule moving in a direction) or rotational kinetic energy (molecule is rotating about one or more axis)
Why do particles have potential energy?
Because of the intermolecular energy between the particles.
What is internal energy?
The total energy the particles have and when a substance is heated we increase its internal energy.
Characteristics of a solid.
Fixed volume and shape, held in position by bonds.
The molecules vibrate around a mean position. The higher the temperature the greater the vibrations.
Characteristics of a liquid.
Fixed volume but can change shape.
The molecules vibrate but not completely fixed in position
Still Strong forces between molecules
Characteristics of a gas.
They will always expand to fill the container
Forces between molecules are weak and they are essentially independent of one another
Occasionally collide
Connection between heat and work
Work is done on a microscopic level - we say heating is taking place. The energy transferred from the heat can increase the K.E or/ and the Potential energy of the particles.
What three things does increases the temperature depend on?
Energy given to the object
The mass
The substance it’s made from
What is Thermal capacity?
The energy required to raise its temperature by 1K
What is Specific heat capacity
The energy required to raise a unit mass of a substance by 1K
What happens when an object is raised above room temperature.
It starts to lose energy until the surrounding temperature is the same as the objects. The hotter it becomes the greater the rate at which loses energy.
Equation for the specific heat capacity in an circuit.
c = (Ix t x V) / m ( T2 - T1)
What occurs when there are two different mixtures at different temperatures?
Energy lost by hot substance cooling down = energy gained by cold substance heating up
Ma x Ca (Ta - Tmax) = Mb x Cb (Tmax - Tb)
What is the universal constant and what is the equation for it?
Universal constant = molar gas constant = R
Units for R: J mol^-1 K^-1
pV/ nT = R
What is an ideal gas?
A gas that follows the gas laws for all the values of p, V, and T
Thus is cannot be liquefied.
What is molar mass and what’s its equation?
It’s the mass of one mole of a substance
No. of moles = number of atoms/ Avogadro constant
When can real gases approximate to ideal behaviour?
The intermolecular forces are small enough to ignore, therefore the pressure/ density of the gas must be low with moderate temperature.