Chapter 14. Temperature Flashcards
(18 cards)
Explain what is meant by thermal equilibrium
When different regions in thermal contact are at the same temperature.
Explain how a thermocouple works
Two different metal wires are twisted together at one end to creat a junction and the other ends are connected to the terminals of a sensitive voltmeter. An e.m.f is produced and the reading depends on the temperature at the junction.
What is a thermometric property?
A physical property on which a particular thermometer is based.
What is a thermometric substance?
The material of which the thermometric property varies with temperature
Show understanding of the difference between temperature and thermal energy
temperature is just a measure of the degree of ‘hotness’ of a body and thermal energy is a measure of the body’s heat energy.
What is the formula for finding an unknown temperature on the empirical centigrade scale of temperature given the value of a thermometric property at that temperature?
θ = 100(Pθ - Pi)/(Ps - Pi)
What is the absolute zero temperature?
The lowest theoretically possible temperature. At this temperature, molecules would have zero kinetic energy. Lowest ammount of internal energy. (-273.15oC)
Show understanding of the thermodynamic scale
This scale starts with its zero at the absolute zero temperature. It does not depend on any property of any substance as it is based on the theoretical behaviour of the so-called ideal gas. The upper fixed point is taken as the ‘triple point of water as this is found to be less dependent on environmental conditions such as pressure. This is taken to be 273.16 units on this scale.
Define one kelvin
One kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water
What is the triple point of water?
The temperature at which ice, water and water vapor are in equilibrium.
Formula for temperature on kelvin from an empirical temperature scale
T = 273.16 * (p/ptr) where p is the reading at that temperature and ptr is the reading at the triple point of water.
Formual for temperature in o</sub>C from K
θ = T - 273.15
Define specific heat capacity
The quantity of thermal energy required to raise the temperature of unit mass of the substance by one degree.
What is the formula linking energy and specific heat capacity?
△Q = mc△θ where Q is energy, m is mass, c is pecific heat capacity and θ is temperature
What is the specific heat capacity of water?
4 200 Jkg-1K-1
Define specific latent heat of fusion
The quantity of thermal energy required to convert unit mass of solid to liquid without any temperature change. △Q = mLf
Define specific latent heat of vaporisation
The quantity of thermal energy required to convert unit mass of liquid to vapor without any temperature change. △Q = mLv
Explain why the specific latent heat of vaporisation is significantly higher than the specific latent heat of fusion.
The thermal energy enables the strong forces that make teh solid rigid between atoms/molecules to be overcome. Forces still exist in liquid and volume does not significantly change but in heat of vaporisation, forces in gases are negligible and atoms/molecules are completely separated, hence more energy is needed.
