Thermal Physics Flashcards
What is the definition of internal energy
Internal energy is the sum of the randomly distributed kinetic and potential energies of all its particles
Describe what happens to the distribution curve of particle speeds as temperature increases
Distribution curve becomes more spread out
What four things determine internal energy of a system
- Temperature (high temp = higher kinetic energy)
- Random motion of molecules
- Phase of matter
- Intermolecular interactions between particles
Describe how the phase of matter effects internal energy
= Gas has highest internal energy
= Solid has lowest
What is the first law of thermodynamics
The internal energy of a system is increased when energy is transferred to it by heating or when work is done on it
What happens to internal energy as a gas expands
Volume increases = work is done BY gas ON surrounds
(its invading which takes energy)
Internal energy decreases
What happens to internal energy as gas is compressed
Volume decreases == Work is done ON gas BY surroundings
Internal energy increases
What is known at absolute zero
0K
All molecules have zero kinetic energy
How can you convert Celsius to kelvin
K = C + 273
Explain a principal in heat transfer
Heat is always transferred from hotter substance to cooler substance
Higher difference in temperature = faster heat transfer
Definition of specific heat capacity
The amount of thermal energy required to raise the temperature of 1kg of a substance by 1C without a change in state
Relationship between specific heat capacity and conductivity
A excellent conductor will have a low specific heat capacity
Definition of specific latent heat
The thermal energy required to chance the state of 1kg of mass of a substance without any change of temperature
Describe how a graph demonstrates specific latent heat
Stair case shape
First horizontal line represents latent heat of fusion (solid to liquid)
Second horizontal line represents latent heat of vaporisation
Describe the graph of specific latent heat in terms of potential and kinetic energy
Angled lines == particles gain Kinetic energy
Horizontal lines == Kinetic energy constant, potential energy increases as bonds are broken
What temperature does water boil
100C
Explain why there is a change in potential energy during a change in state
- Potential energy is due to separation and intermolecular bonds
During change in state separation will change
AND
Bonds will be broken or made
What is Boyle’s law
- If the temperature of an ideal gas is constant
== Pressure is inversely proportional to volume
How can you write boyle’s law as an equation
PV (1) = PV (2)
What is Charles’s law
- If pressure of an ideal gas is constant
== Volume is proportional to temperature
How can you write Charles’s law as an equation
V/T (1) = V/T (2)
Describe the graph for Charles’s law (For both C and K)
Straight line through origin for C
Straight line that cuts x axis at -273 for K
What is the pressure law?
- Ideal gas at constant volume
== Pressure is proportional to temperature
How can you write the pressure law as an equation?
P/T (1) = P/T (2)
Graph for pressure law for both K and C
Same as Charles’s law
Straight line through origin for C
Straight line that cuts x axis at -273 for K
What are the assumptions used to derive the kinetic theory of gas equation
RAVED
R = Random motion
A = Attraction, none between particles
V = Volume, molecules/particles have negligible volume
E = Elastic collisions, kinetic energy conserved
D = Duration of collisions is very short compared to time between them
What is an empirical law
- Based off of observations and evidence
- Predict what will happen but do not explain
Example: Gas law
What is a theory
- Based on assumptions and derivations from knowledge
- Both predict and explain
Example: Kinetic theory
What is meant by Brownian motion
- Type of movement of any particles suspended in a fluid
Essentially a random motion
How does Brownian motion support kinetic theory model of different states of matter
- Einstein explained the random motion of object in fluid
- Is due to the result of collisions with fast, randomly moving particles of the fluid
