Thermal Energy Flashcards
What is thermal energy
Thermal conduction is diffusion of thermal energy across different materials.
What happens when heat is gain in thermal conduction?
When gain material heat (temperature increase) the kinetic energy of particles within material increase. This because vibration of particles increases
What happen when heat is lose in thermal conduction?
When loses material heat ( temperature decrease ) the kinetic energy of particles said material decrease. This because the vibration of the particles decrease.
What happen if the thermal conduction has a large temperature?
A large temperature difference means increase in the rate of thermal conductivity.
What does thermal conduction depend on ?
The rate of thermal energy transfer by conduction is dependent on the temperature difference of part of the object.
What varies in thermal conduction ?
The rate of Thermal conduction varies for each materials.
What happens if thermal energy is better at transferring?
The better material are transferring thermal energy, the greater the thermal conductivity.
What is Conduction of metals ?
Metal have significant higher thermal conductivity than metals.this because there is a second process transferring the energy to the metals. This energy transfer free electrons. Metals contains lattice metals ions surrounded by a sea of free electrons. The same metal allow electrical conductions. When the meat is heat the electrons rapidly gain energy and can pass along metal carry thermal energy. This process is far quicker than lattice vibration method above and metal make a good conductor
What is Convecti of current ?
When a substance increase in temperature it expands and when it cools down it contrast. During expands the particles move further apart and the density decreases. During contrast the particles move closer together and the density increase. This behavior can transfer heat energy by producing convection current and there are flow of particles within the substance.
What can convection current in air be produced by :
When the air is heated the particles move further apart from each other and expands.
Because the warmer air less dense the cooler, surrrounding air float upward carry heat energy with it.
The air becomes less denser
The air spread out and rise, loses energy and cools.
As the air cools the particles move closer together so there air becomes dense.
The air sunk back downward and cycle continues
What is Infrared Radiation?
An object is constantly emitting and absorbing IR radiation from the surface.
Warm up : when warm up an object it absorbing IR radiation at a grater rate than it emitting. A cool drink place in direct sunlight warm up rapidly.
Cooling down: all object will cool down when emitting more IR radiation than absorbing it. Freshly cooked food place in a room would gradually cool down to room temperature.
Constant temperature: if the rate of absorption and the rate of emission is the same the object will not gain or lost energy. It will stay in a steady temperature. A object in room temperature stay in room temperature. The same temperature as each other
What are some properties of surface?
Absorption and emission happens on the surface of an object. The surface is very important.
The surface area of an object: A large surface area will allow energy to escape or to absorb rapidly.
The colour of the surface: the darker surface are much more better absorbing and emission of IR radiation than white surface. If you step outside wearing black clothes on we will feel the effect immediately. Your clothes start to feel heated.
Vacuum flask
Vacuum flask is prevent as much thermal energy transfer as possible. To do this reduce conduction, convection, radiation and evaporation possible.
The main chamber is glass ( a poor conductor) with a vacuum is between two layers. A vacuum contains no particles cannot be no convection or conduction transfer to thermal energy. Thermal energy can be transfer around the glass layer by conduction but this process is a slow process.
The inside of the glass is coated in silver to reduce radiation. The surface are poor emitter and absorb of radiation. So there is very little transfer of energy in them.
A hallow plastic cap is used for evaporation.
What Solar heat water ?
Many house heat water using solar energy. Cool water is neither pumped or driven by convection current though pipes on the roof. The pipes are painted black to absorb energy from the sunlight and the energy is transfer to the water passing through them.
What is Greenhouse gas and global warning ?
The earth absorb energy radiation by sun this energy warm up. The sun arrive as visible light and short wavelength infrared radiation which passes through the atmosphere. The surface of the earth remits longer wavelength infrared radiation. The some of this reflected back on the to the surface of the earth by greenhouse effect such as carbon dioxide and methane. The greenhouse effect tends to maintain balance.the earth has remained constant temperatures for several thousand years.
However human activity such as burning fossil fuel increases crop production, deforestation, livestock increasing the amount of greenhouse gases on the atmosphere. This cause more heat energy to be trapped and results in all over increase in the atmospheric and ocean temperatures.
