thermal physics EQ Flashcards
Define brownian motion.
the random motion of a particle as a result of collisions with surrounding gaseous molecules
Explain in terms of the kinetic theory why the pressure of a gas in a cylinder falls when gas is removed from the cylinder.
→ Gas pressure is caused by force exerted by gas molecules colliding with surface of wall
→ when gas is removed there are fewer molecules in the cylinder
→ frequency of collisions between gas molecules and wall decreases
→ force exerted decreases, pressure decreases
State two quantities which increase when the temperature of a given mass of gas is
increased at constant volume.
→ pressure
→ average kinetic energy
What does the average kinetic energy per molecule depend on?
temperature only
State what is meant by an elastic collision.
a collision in which kinetic energy is conserved
State three assumptions made in the kinetic theory of gases.
→ volume of molecules is negligible
→ collisions are elastic
→ motion of molecules is random
Define what is meant by thermal equilibrium.
when two substances in physical contact with each other no longer exchange any heat energy & both reach an equal temperature
Explain why the pressure of a gas in a sealed container decreases when temperature falls.
→ Ek decreases
→ fewer collisions per second
→ rate of change of momentum decreases
State what the total internal energy of an ideal gas is equal to and why.
→ equal to the total kinetic of molecules
→ molecules have no potential energy as there are no attractive forces
what is pressure x volume equal to?
work done
Explain why the volume occupied by an ideal gas increases when it is heated at constant
pressure.
→ constant pressure
→ faster molecules so more momentum change per collision
→ greater volume to maintain same pressure
