Chapter 10 - Transfer of Thermal Energy Flashcards
Thermal energy ALWAYS transfer from ___ to ____
New flow of thermal energy occurs only when ____
A region of higher temperature to a region of lower temperature.
When there is a temperature difference
Heat can be transfer in 3 ways, what are they?
Conduction
Convention
Radiation
Define conduction
Conduction is the transfer of thermal energy through a medium WITHOUT any flow of the medium
Different materials transfer heat at _______ rate
DIFFERNT
Normally, metals are _____ conductor of heat
GOOD
Normally, non metals are _____ conductor of heat
POOR
Heat transfer: What is the difference between metals and non-metals
Metals have free electrons which can move randomly among the atoms of metal
How heat is transfer in NON-METAL?
The heat energy from the heat supply flow to the particles of the non metal at one end, causing the particles at that end vibrate vigorously about their fixed positions
The vibrating particles collide with the neighboring particles, making the vibration more vigorously. During the proceed, the kinetic energy of the vibrating particles at the hot end is transferred to the neighboring particles. This results the neighboring region to be come hotter
(Thermal energy has been transfer without the transfer of the particles.
Eventually, the particles at the cooler end also vibrates vigorously and that results in the cooler end become hotter.
How heat is transferred in METAL
The heat energy from the heat supply flow to the particles of the metal at one end, causing the particles at that end vibrate vigorously about their fixed positions
The vibrating particles collide with the neighboring particles, making the vibration more vigorously. During the proceed, the kinetic energy of the vibrating particles at the hot end is transferred to the neighboring particles. This results the neighboring region to be come hotter
(Thermal energy has been transfer without the transfer of the particles.
Eventually, the particles at the cooler end also vibrates vigorously and that results in the cooler end become hotter.
In addition, free electron diffusion take places in metals, which is able to transfer heat much faster than the vibration of particles. The free electrons are heated up one end. They absorb thermal energy and thus gain kinetic energy.
The free electrons move at a greater speeds and move to the cooler region. As these electrons move, they collide with the atoms in the cooler region, making them vibrate more vigorously. During the process, thermal energy and some of the kinetic energy is transferred from the electrons to the atoms, making the cooler end hotter.
Why in the transfer of heat in liquid and gas are not as efficient as in solid?
The particles in liquid and gas are further apart as compare to the particles in solid. Hence, the collision between particles will be less frequent. Thus, the kinetic energy transferred from the particles at the hotter end to the particles at the cooler end is much slower.
Definition of convection
Convection of thermal energy by means of convection currents in a fluid (Liquid or Gas), due to a difference in density
How does the heat transfer in the kettle works to boil the water?
The heat transfer in the kettle with water mainly by convection. The heating coils, which is at the bottom of the kettle, gain thermal energy when the power supply is turn on. The thermal energy is then transferred to the water molecules that come in contact with the heating coils by conduction. The water molecules at the bottom are thus heated up. This causes the water molecules to gain thermal energy and expand. Density = Mass/Volume, thus the water molecules have a lower density than the water molecules on top of them. The hotter water molecules will then rise up vertically and the cooler water molecule at the top will sink and rush in to replace the hotter molecules. The motion of the water molecules result in a convection current and the water is continuously heated to a higher temperature and eventually reach 100 degree celsius and boiling will take place.
Why convection does not occur in solids?
Convection involves the BULK movement of the fluid that carries thermal energy. However, for solid, the thermal energy is transferred from one particle to the other through vibrations, with any bulk movement of the particles
Define Radiation
Radiation is the transfer of thermal energy in a form of electromagnetic waves such as infrared radiation, WITHOUT an aid of medium
All objects emit ________, this emission cause the _______ of the objects to fall
Infrared radiation, Temperature
