thermal stuff Flashcards
what is internal energy
sum of random kinetic and potential energy of all molecules in a system
explain how internal energy of a gas is different from that of liquid
higher temp so higher KE; higher PE due to latent heat
explain why gas pressure increases with temperature; use the kinetic theory of gases
higher temp means higher speed of molecules; this means more frequent collisions; also larger change in momentum with each collision
describe an electrical experiment to find specific heat capacity of a sample of oil; use a labelled diagram
see book
explain what happens to the temperature of a substance as it changes phase
temperature stays constant; energy taken in is converted to potential energy (latent heat)
what are the assumptions made in the ideal gas model
collision with container is elastic; force between molecules is zero except in collisions; volume of molecules negligible compared to container; time of collisions negligible compared to time between collisions
explain gas pressure in terms of newton’s laws of motion and the ideal gas model
momentum of molecule changes when colliding with wall; change in momentum over time = force on molecule; force on molecule equal and opposite to force on wall; sum of forces on wall / area = pressure
a gas molecule hits a wall with speed v and momentum mv; explain why it rebounds with speed v and gets an impulse of 2mv
collision is elastic so velocity becomes -v; change in momentum = mv - (-mv) = 2mv
what is boyle’s law
for a fixed mass of gas at constant temp; pressure x volume = constant
what is specific heat capacity
energy required to raise temperature of 1kg of a material by 1K
what is absolute zero
lowest limit for temperature; minimum internal energy
why does a body’s internal energy increase as its temperature increases
its molecules gain higher KE; internal energy is sum of KE and PE
how is absolute zero estimated using a graph of temperature and pressure
gradient from line of best fit is used; temperature extrapolated for when pressure becomes 0
what is the root mean square of a set of numbers
square root of the mean of the squares of each number
how to calculate the boltzmann constant
molar gas constant (R) / avogadro constant (NA)
what is specific latent heat of fusion
energy to convert 1kg of substance at melting point from solid to liquid
a block of paraffin wax melts at a constant temperature of 52 degrees; explain the change in its internal energy
temp stays constant => KE stays the same; melting => PE increase due to latent heat of fusion; internal energy increase
