Heat
Heat
Heat is the opposite of cold. In thermodynamics heat
means energy which is moved between two things when one of them is hotter than
the other.
Adding heat to something increases its temperature, but heat is not the
same as temperature.The temperature of an object is a measure of
the average speed of the moving particles in it.
The energy of the particles is called the internal
energy When an object is heated, its internal energy can increase to make
the object hotter. The first law of thermodynamics says that the
increase in internal energy is equal to the heat added minus
the work done on the surroundings.
Thermal energy is the type of energy that a thing has
because of its temperature. In thermodynamics, thermal energy is
the internal energy present in a system in a state
of thermodynamic equilibrium because of its temperature.That
is, heat is defined as a spontaneous flow of energy (energy
in transit) from one object to another, caused by a difference in temperature
between two objects; so objects do not possess heat.
Properties
of Heat:
Heat is a form of energy and not a physical substance.Heat has
no mass
Heat can move from one place to another in different ways:
· Conduction
· Convection
· Radiation
The measure of how much heat is needed to cause some change in
temperature for a material is the specific heat capacity of the
material. If the particles in the material are hard to move, then more energy
is needed to make them move quickly, so a lot of heat will cause a small change
in temperature. A different particle that is easier to move will need less heat
for the same change in temperature.
Specific heat capacities can be looked up in a table,
like this one.
Unless some work is done, heat moves only from hot things to
cold things.
Measuring
Heat
Heat can be measured. That is, the amount of heat given out or taken in can be
given a value. One of the units of measurement for heat is the joule.Heat is usually measured with a calorimeter, where the energy in a material
is allowed to flow into nearby water, which has a known specific heat capacity.
The temperature of the water is then measured before and after, and heat can be
found using a formula.
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