Chapter 14, Thermal Physics Flashcards
What is the triple point of a substance?
The specific temperature and pressure where the substance can exist as a liquid, solid and gas simultaneously.
What is the zeroth law of thermodynamics?
If an object A is in thermal equilibrium with an object B which is in thermal equilibrium with an object C then A and C are also in thermal equilibrium.
How do you convert between Kelvin and degrees Celsius?
K = C +273.
What is Brownian motion?
It is the way in which particles in a liquid or the air appear to drift at random but is actually caused by the large quantity of smaller particles that make up the liquid or gas colliding with it, this can be observed in a smoke cell or with dust on water.
Definition for internal energy?
The sum of the kinetic and potential energies of atoms or molecules within a substance.
What would the temperature against time graph of a substance which is being heated at a constant rate look like?
A series of straight lines, increasing between states but constant as a phase change occurs.
Why does water make a good coolant?
Because it has a very high specific heat capacity.
What is the definition of specific heat capacity?
The energy required to increase the temperature of unit mass by unit temperature (unit J /Kg /K).
What does the equation E = mcΔθ show?
The energy released/used by a material is equal to its mass * specific heat capacity * change in temperature.
What experiment using a heater can be carried out to measure specific heat capacity?
Take the material you want to measure the specific heat capacity of, drill two holes and record the weight, put a thermometer and heater in each hole and surround the material in an insulator, The energy provided by the heater is equal to current * voltage * time and therefore c = (IVt) / (mΔθ), a graph of θ against time allows a more accurate result from a measurement of the gradient.
How can mixing two materials allow you to find the specific heat capacity of one of them?
Since the energy transferred between the two materials is equal, m1 c1 Δθ1 = m2 c2 Δθ2 so by knowing the masses of the two materials and the starting and finishing temperature of each material and a value of c for one material you can re-arrange for the other c value, this is often done with solids in water.
What is specific latent heat?
The energy required per unit mass to change the phase of a material while at a constant temperature (energy goes to changing electrostatic potential energy).
What is the name for the specific latent heat value from a solid to a liquid?
Specific latent heat of fusion.
What is the name for the specific latent heat value from a liquid to gas?
Specific latent heat of vaporisation.
How can the specific latent heat of fusion be measured?
By using a heater circuit and then using L = (IVt) / m.
