HEAT - TEMPERATURE AND SCALES
Real time Applications:
* In medical field thermometers are used by the doctors to know the temperature of a patient.
* In industries with the help of heat energy many metals are going to convert into thin sheets and wires.
* In mechanics heat plays a wide role in running a motar vehicle.
* In factories the temperature of a resultant mixture can be found by using calorimetry principles.
* Calorimetry is used to determine the calorie content of a food.
* In chemical laboratories heat change is a fundamental to understand chemical reactivity and physical property of a given material.
Important Formulae
1. \(\frac{{C - 0}}{{100}} = \frac{{F - 32}}{{180}} = \frac{{R - 0}}{{80}} = \frac{{K - 273}}{{100}}\)
2. Q = ms\(\Delta t\)
3. Q = m.C.
4. Q=mL
5.Principle of calorimetry:
Heat energy given out by hot body = Heat energy absorbed by cold body.
Heat and Temperature
1. Heat is a form of energy which causes in us the sensation of hotness (or) coldness.
2. Temperature is the degree of hotness (or) coldness of an object.
3. Following points sum up the flow of heat energy from one body to another body.
i) Heat energy always flows from a body at higher temperature to a body at lower temperature till equilibrium is reached.
ii) At equilibrium temperature, the heat energy does not flow.
iii) The rate at which the heat energy flows from a hot body to a cold body depends upon the difference in temperatures of both the bodies.
iv) The amount of heat energy flowing into the cold body is always equal to the amount of heat energy supplied by the hot body.
i.e Heat energy lost (given out) = Heat energy gained OR absorbed.
Effects of heat energy :
i) Heat energy brings about change in temperature.
ii) Heat energy brings about change in dimensions.
iii) Heat energy brings about change in the states of matter.
iv) Heat energy bring about chemical changes in matter.
Units of heat :-
system Unit Symbol
C.G.S calorie Cal
S.I joule J
1 Calorie = 4.18 J Kilo calorie = 4180 J
Units of temperature :
Generally temperature is measured in degree Celsius ( 0C).
In S.I system temperature is measured in kelvin (K).