Thermal Physics Flashcards
Why does melting take less time(or energy) than boiling?
When a solid melts, the molecules are still bonded to most of their immediate neighbours and when a liquid boils, each molecule breaks free of all it’s neighbours. Boiling involves breaking more bonds.
The point where the state of a substance is changing, the temperature doesn’t change because…?
The energy goes into breaking bonds.
Temperature is a measure of?
Average Kinetic energy.
What is internal energy?
The internal energy of a system is the sum of the random distribution of kinetic and potential energies of its atoms or molecules.
First Law of Thermodynamics.
Increase in internal energy = energy supplied by heating + energy supplied by doing work. (U = q + w)
Explain thermal energy?
Energy flowing from a region of higher temperature to a region of lower temperature.
What is thermal equilibrium?
When two objects in contact with each other, are at the same temperature, there will be no net transfer of thermal energy between them.
What is absolute zero?
The temperature at which all substances have the minimum internal energy. It is not possible to remove any more energy from the substance.
What is said about the thermal dynamic scale?
An absolute scale as it’s not defined in terms of a property of any particular substance. It is based on the idea that the average kinetic energy of the particles of a substance increases with temperature.
Problems with Celsius scale.
It depends on melting and boiling point of pure water.
The average kinetic energy is the same for all substances at any particular thermodynamic temperature as….?
It does not depend on the material itself.
Triple point of water.
0.01 C.
Properties that can be used as the basis of thermometers?
- Resistance of an electric resistor or thermistor.
- Voltage produced by a thermocouple.
- The color of an electrically heated wire.
- The volume of a fixed mass of gas.
How does a thermocouple work?
It has two different metal wires(x & y) x has metal y connected at it’s two ends, forming 2 junctions. Difference in temperature between them produces an e.m.f between them, which can be measured using a voltmeter.
Equation for specific heat capacity.
c = E/mΔT(tetha)
