H208 Temperature and Ideal Gases Flashcards
What happens when two bodies are in thermal equilibrium?
When two bodies are in thermal equilibrium, there is no net flow of thermal energy between the bodies that are in thermal conact because they are at equal temperature.
Define heat.
Heat is thermal energy that flows from a region of higher temperature to a region of lower temperature.
Don’t say “heat energy” as heat already means thermal energy
Define thermometric property.
Thermometric property is a property of a substance that changes with temperature.
What conditions should a suitable thermometric propety follow?
- vary continuously and uniquely with temperature
- change sufficiently noticeably
- be reproducible
What is the formula to find T unknown by measuring its thermometic propoerty X known at the unknown temperature and using the known values T0 and T100?
T unknown = (X unknown - X0 / X100 - X0) x 100 degree celcius
Why may temperature measurements form empirical cenigrade scales across different types of thermometers not agree?
- Thermometric properties are assumed to vary linearly with temperature, whcih is not the case in reality
- Temperature measurements agree only at fixed points of ice point and steam point
Define absolute zero.
Absolute zero is define as the zero point (0K). It has a fixed point on the bsolute temeprature scale. A substance at absolute zero has minimum internal energy.
State the conversion scale from kelvin to celcius.
T/K = T/degree celcius + 273.15
Defien ideal gas and state the equation of state.
An ideal gas is a gas that obeys the equation of state pV=nRT at all pressures, volumes and temperatures.
p = pressure, V = volume, n = amount of gas in moles, R = 8.31 and T is the thermodynamic temperature in kelvins
What is another equation of state that uses the actual number of gas particles N rratehr than the amount of gas in moles?
pV = NkT
where k is the Boltzmann’s constant: 1.38 x 10^-23
Define one mole.
One mole of any substance contains 6.02 x 10^23 particles (Avogardo’s number)
State the motion of gas particles.
- it is random and hphazard
- it has a constant speed in a straight line between collisions
- it shows a distribution of speeds
State the assumptions behind the Kinetic Theory of Gases.
- All collisions that the gas molecules undergo are elastic
- Large numbers of gas molecules are in continuous random motion
- No intermolecular forces except during collisions
- Total volume of molecules negligible compared to volume of containing vessel
- Time of collisions negligible compared o time between collisions
Why does gas particles exert pressure on the wall of its container?
- Gas particeles are in continuous random motion and experience changes in momentum when they collide with the inner walls of the container
- By Newton’s 2nd Law, a gas particles experiences a force from the rate of change in momentum during the collision
- By Newton’s 3rd Law, there is a force exerted on the wall that is equal in magnitude and opposite in direction to the foce exerted on the gas particle
- Hence, an average force is exerted over the area of the wall due to many collisions from many gas particles ina random distribution of velocities
What is the formula for the kinetic theoy of gases?
pV = 1/3Nm(c^2)
or
p = 1/3 (Density) (c^2)
N = actual number of particles, c = mean square speed of the gas particles
State the formula of mean translational kinetic energy.
Ek = 3/2kT
The mean translational kinetic energy of molecules of an ideal gas is directly proportional to the thermodynamic temperature of the gas.
