Chapter 2: Temp and transfer of thermal energy Flashcards
Define temp and state its S.I unit
Measure of the average K.E of the molecules in a substance.
A measure of the degree of hotness.
It is a scalar quantity.
S.I = K
What is Thermal energy (TE) and how is it transferred?
It is the non-mechanical (happens by itself) transfer of energy from an object of higher temperature to one of lower temperature
How does a liquid in glass thermometer measure temp?
Variation of a volume of fixed mass of liquid (e.g alcohol or mercury)
What condition is necessary for a physical property to be used to measure temperature within a specified range?
Physical property used must have each value of the property correspond to a unique value of temperature within the specified range
e.g, between 0-8˚C the density of water is not unique, so we cannot use it to measure temp
between 0-4˚C water increases in vol and thus decreases in density (mass is still the same)(ice floats on water)
Compare celsius scale to kelvin scale
Celsius:
- Uses ICE POINT and STEAM POINT of water as fixed points
- Ice point (0˚C) = temp pure ice melts
- Steam point (100˚C) = temp pure water boils
(all @ S.T.P)
Kelvin:
- Uses ABSOLUTE ZERO and TRIPLE POINT OF WATER as fixed points
- Absolute zero (0K) = theatrical value of the lowest temp any substance can reach
- Triple point of water (273.16K) = temp where water exists in all 3 phases
Why does the Kelvin scale use triple point of water?
It is precisely reproducible
State relation of celsius and Kelvin scales of temp
T(K) = T(˚C) + 273
0˚C = 273K (ice point)
State relation between the temp diff. of 1˚C and 1K
1K change in temp is EQUAL to 1˚C change
(doesn’t mean the values are the same, but the amount of change they go through is equivalent)
What do we assume when calibrating a liquid in a glass thermometer?
Length of liquid in tube changes linearly with the temp between the fixed points
Formula for calibration
T = (length of T - length of lower limit/ length of upper limit - length of lower limit) x (upper limit - lower limit) + lower limit
Suggest what is implied when two objects are in thermal equilibrium (the same temp)
There is no net transfer of thermal energy
Describe how conduction transfers TE
Through collisions between neighbouring particles
- particles bump into each other and pass the energy
Describe how convection transfers TE
Through movement of a fluid due to density differences
- fluid = gas or liquid
- first particle takes the energy and moves with the energy
Describe how radiation transfers TE
Through electromagnetic waves
- doesn’t need a medium
- can take place in a vacuum
State the 7 electromagnetic waves
1) Gamma
2) X-ray
3) UV
4) Visible light
5) Microwave
6) Infrared
7) Radio waves