thermal processes Flashcards
what is thermal equilibrium?
describes a state in which two or more objects have the same temperature and that there is no net transfer of energy between them.
how is heat transferred?
transferred from a region of higher temperature to region of lower region temperature until boh regions have same temperature.
how is energy transferred (hotter - colder)
The hot ___ and surrounding air form a system.
Hot __ was at a higher temperature than the surrounding air.
Hence, the difference in temperature caused energy to be transferred from hot ___ to surrounding air
The temperature of the ___ decreased until it was at the same temperature as surrounding air. Energy in internal store of __ decreases.
Temperature of tea decreased until it reached thermal equilibrium.
how does energy transfer from (colder to hotter)
iced__ and the surrounding air formed a system.
Iced ___ was at lower temperature than the surrounding air.
Hence, the difference caused energy to be transferred from surrounding air to ice ___
The temperature of coffee increased until it was the same temperature as surrounding air. Thus, energy in internal store of coffee increased.
The temperature of coffee increased until it as the same temperature. It has reached thermal equilibrium.
what is the definition of conduction?
conduction is a process of energy transfer where energy is transferred through vibration and collisions from one particle to another.
how does conduction take place in solids? (non-metal)
energy is transferred to the ___ by heating. The particles nearest to the heat source will vibrate more vigorously about fixed positions.
Thus, through collisions, energy is being transferred from the more energetic particles to less energetic particles to the right.
Hence, as more energy is being transferred from left to right, the particles here begin to vibrate more vigorously. Temperature at the end of the rod increases.
how does conduction take place in solids? (metals)
Energy is transferred to rod by heating. Particles nearest to heat source will vibrate more vigorously about fixed position.
The free electrons at this heated end gains energy from interacting with particles.
The small size and high speed of electrons allow them to move easily and quickly to the cooler end and transfer energy to particles there.
The free electrons moving here are collectively slower after colliding and transferring their energy to particles at this cooler end.
Particles vibrate more vigorously. The temperature of this end of rod increases.
what is convection?
convection is a process of energy transfer by means of convection currents of a fluid, due to difference in density.
what is the process of convection? (boiling pot)
the liquid at the bottom of the pot expands due to heating via conduction through bottom of the pot.
The warmer and less dense liquid starts rising towards the top.
At the same time, the surrounding denser liquid sinks to take the place of the rising liquid.
The process repeats and causes convection currents. The circulating convection currents carry warmer liquid away from heat source and cooler liquid towards it. This allows the pot to gain internal energy.
what is radiation?
the process of energy transfer by electromagnetic waves. It does not require a medium
what can affect radiation? (surface temperature)
higher temperature of surface, higher emission/ absorb energy at higher rate of radiation
what affects radiation? (surface area)
bigger the surface, higher the emitted energy via radiation
what affects radiation (surface colour and texture)
shiny and smooth, light coloured surface is a poor absorber and emitter of radiation.
dull and rough, dark-coloured surface is good absorber and emitter of radiation.
applications in daily life - conduction (windows)
double/triple glazed windows
Air is a poor thermal conductor. A thin layer of air is trapped between two glass panes reduces energy transfer. Energy transfer through window is further reduced with three glass panes/ two layer of trapped air.
application in daily life - convection (electric kettles)
heating element placed at the bottom of the kettle. When the kettle switched on, water around the heating element heats up and expands. Heated water rises while cooler part sinks to replace the heated water. The convection current set up, allows water in kettle to be heated more quickly and evenly.
