Thermo Dynamics Flashcards
(20 cards)
what are the three types of particle arrangement?
they are;
solid
liquid
gas
what are the properties of solids
has definite shape and volume
hard and rigid (typically)
strong force required to change shape
incompressible
what are the properties of liquids
has definite volume but no shape
high density
incompressible
is fluid.
what are the properties of gases
no definite shape or volume
low density
compressible
is fluid
what are convection current
Warmer regions of a fluid are less dense than cooler regions of the same fluid
The warmer regions will rise because they are less dense
The cooler regions will sink as they are more dense
This is called convection
The steady flow between the warm and cool sections of a fluid, such as air of water, is called a convection current.
on what principle does a thermometer work
Thermometers work on the concept of expansion and contraction
The expansion/contraction of the substance in the thermometer must be proportional to the change in temperature
what is macroscopic energy
It is defined as being due to the motion (velocity) in location (height) of an object in a gravitational, electrical or magnetic field.
An example would be throwing a basket ball into a hoop
what is the formula for macroscopic energy
Emacro = EK(macro) + EP(macro)
what is microscopic energy
When we consider microscopic energy, we are considering the particles inside something
These particles may be atoms, molecules, electrons or other particles
The total microscopic energy is made up of the microscopic kinetic energy and the microscopic potential energy.
what is the formula for microscopic energy
Emicro = Ek(micro) + EP(micro)
what is internal energy
Microscopic energy is the internal energy of a substance or system
In thermal physics we are not concerned so much with the chemical and nuclear potential energy as they are not considered to change in the contexts that we are dealing with. The energy in the chemical bonds and in the nucleus doesn’t change for normal heating and cooling as no chemical reactions takes place.
If we leave out these forms of energy, we are left with thermal energy. For senior physics we use the terms ‘thermal energy; and ‘internal energy’ interchangeably
what is the formula for internal energy
U = EK(micro) + EP(micro)
what is the formula for a change in internal energy
ΔU = Δeth
what is the formulas for the total energy in a system
Esys = Emacro + Emicro
Esys = EK(macro) + EP(macro) + EK(micro) + EP(micro)
However, when we are looking at internal energy, we assume that the object is stationary, so:
ΔEsys = ΔU
what is thermal energy
Recall that thermal energy is related to kinetic energy
So, if the kinetic energy of particles in a substance increases, so does its thermal energy (and, of course, its internal energy
Heating is the term used when some of the thermal energy is transferred
what is kinetic energy
If i spray some deodorant at the back of the room, after a few minutes you will be able to smell it.
The particles would have taken a zigzag path to get to your nose. The gas particles actually move at something like a few hundred meters per second, but they don’t go far before colliding (elastically) with each other and the air about them. They collide about 6000 times per second and travel a long, long distance to get the front of the room
So, we can say that gas particles are moving. They can vibrate, rotate and go from one place to another. In other words, the gas particles can have kinetic energy (Greek kinema=’motion’).
As you heat up a gas, the speed of the particles, and hence their kinetic energy, increases
how does kinetic energy relate to temperature
In the past you learnt that kinetic energy (KE) relates to the mass and speed of an object. You learnt the formula KE=1/2 m v2. this is the macroscopic kinetic energy
When we are looking at particles we need to consider the microscopic kinetic energy. We can say that microscopic kinetic energy is directly related to the temperature of the system.
what is heat capacity
This means water has twice the Capacity to absorb and store heat energy as oil
Materials vary quite widely as to the amount of heat they can absorb for the same temperature rise. There are no simple patterns in this although metals tend to have low capacity.
what are factors that resist the heating up of a object
Depends on
Mass
§ More mass = more particles = more heat needed to move all particles
Type of material
Heat capacity = how much heat a material absorbs and store
§ Great capacity = they absorb a lot of energy (difficult to heat up)
§ Less capacity = they don’t absorb lots of energy )easy to heat up)
○ How much the temperature is raised
what are the formulas for heat capacity
- Energy = mass x SHC x temperature change
- E = m x c x theta
○ E = energy (j)
○ M = mass (kg)
○ C = heat capacity (j/kg C)
Theta = temperature change (C)
- E = m x c x theta
