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Terms in this set (17)
Form of energy
Hotness or coldness of an object
Particle theory in relation to heat
States that matter is made up of very tiny particles and depending on how far apart these particles are the substance cab be a solid, liquid or gas. When things are heated up, the particles begin to vibrate against each other causing friction which leads to forms of heat energy
Specific heat capacity
The heat required to raise unit mass of a substance by unit temperature interval under specified conditions,usually measured in joules,per Kelvin or per kilogram
Heat is measured in joules
Because it is a form of energy
Conduction, convection, radiation
There are three forms of heat energy
How heat energy is transferred through solids. Solids can conduct heat better than others. E.g. a metal rod is in contact with a hot flame quickly becomes hot. Heat energy is rendered among the metal rod. As the rod is heated,the particles move faster, and bump into neighboring particles, making them move faster too.
How heat energy is transferred through liquids and gases. Convection currents can also occur in air. E.g. when air is heated it's particles move faster and it expands. The air becomes less dense and floats upwards. Hot air floats up, cools down and cold air comes down. Uses of connection currents include a furnace, convection oven, heaters, hot air balloons, etc. Thr core of the earth is very hot.
How heat energy is transferred without the use of particles. E.g . There are no particles between the sun and the earth and yet the heat energy still comes to earth because of radiation. It is the tender of heat via electromagnetic waves through a vacuum (without the need of matter). The sun sends out waves of energy in all directions. It isn't just the sun that uses radiation, things like a fire or stove can as well.
How does convection work
Convection happens in fluids (liquids and gases). The heat energy moves through thr material as the particles in the material move through the material. Hot liquids and gases rise because when they are heated they expand and become less dense. The less dense warm liquid or gas then floats up through the more dense cold liquids and gases. Cold liquids and gases sink because when coooled they contract and become more dense. The more dense cold liquids and gases sink down through thr less dense warm liquids and gases. These changes in density cause the convection currents in the liquid or gas.
good conductors/poor insulators
some types of material allow heat to travel through them easier and quicker than others. It is because they have free electrons that can move around easily. We call these heat conductors. E.g. metals and Glass at hot temperatures. A material cannot be a good insulator and a good conductor, only one or the other .
Good insulators/poor conductors
Materials which have electrons with very little freedom to move around are called insulators. E.g. plastics, glass at room temperature, air, diamond, paper, dry wood, stone. Water is special, it is a better heat conductor than wood, stone or plastic but not as goof as metals. Water has a hidden feature where it can cool by evaporation or boiling and is used to put out fires.
Absorption, transmittion and reflection
A light wave could be absorbed by an object, in which case it's energy is converted to heat. The light wave could be reflected, or transmitted. Reflection and transmission of light waves occur because the frequencies of the light waves do not match the natural frequencies of vibration of the objects.
How microwaves work
Microwave ovens take advantage of the behaviour of eater molecules when subjected to electromagnetic eaves found in the microwave band. The microwave sends out self contained radiation which 'excites' the water molecules and makes them vibrate faster. This in turn creates friction and the friction changes into heat energy.
Good absorbers and emitters- colour wise
The colour black is a good absorber and emitter of radiation, where as the colour white is a poor absorber and emitter of radiation.
In what state each form of heat transfer happens
Conduction is when heat glows through a heated sokI'd. Convection is when heated particles transfer heat to another subjstanfe such as cpoking, including the use of liquids or gases. Radiation is when heat is transferred rhriugh electromagnetic waves, such as from the sun. Radiation can transfer through empty space, while thr other two methods require some form of matter contact for the transfer.
Control of heat e.g. thermos flask
Spent hinge like a thermos flask or a cat engine can control the transfer of heat by using a vacuum, which simply means the absencse of air. A thermos is a bottle with a double walled container inside of it. The air between the two walls is sucked out during construction, creating a vacuum. Instead of containing down kind of heating element to keep hot things hot and cold things cold, a thermos is designed by not allowing heat to escape. Heat can be transferred through the air. To keep heat from escaping, you need insulation. The best insulator possible is a vacuum, because there is no air. If there is no sir to transfer heat, then the heat is retained where it is.
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