HEAT AND TEMPERATURE

Summary of heat and temperature

Solved exercise of heat and temperature

HEAT AS FORM OF ENERGY

Summary

Heat: The sum of kinetic energy of all the molecules in a matter. As heat is a form of energy, the unit of energy itself is the unit of heat. So, S.I. unit of heat is joule (J).

Sources of Heat

1.Sun is the primary source of heat energy.

 2. Heat is obtained by burning fuel.

Example : wood, kerosene, L.P.G., Coal and petrol are some commonly used fuel.

3. Electricity produces heat.

TEMPERATURE

Measuring temperature

The measure of degree of hotness of a body is called temperature. Temperature is defined as the average kinetic energy of the molecules.

Average kinetic energy= Sum of kinetic energy of all the molecules

kinetic energy

Differences between Heat and temperature

Heat Temperature
1. Heat is a form of energy.1. Temperature is the measure of degree of hotness.
2. S.I. Unit of heat J (joule)2. S.I. Unit of temperature is K (kelvin).
3. The sum of kinetic energy of all the molecules in a matter.3. The average kinetic energy of the molecules.

Measurement of Temperature

Temperature is measured by a device called thermometer. Thermometer is an instrument that measures the temperature of a system quantitatively. The most commonly known thermometers are laboratory thermometer and clinical thermometer.

1.Laboratory Thermometer

Laboratory thermometer

Laboratory thermometers are devices used to measure temperature. There are many types of lab thermometers such as differential, mechanical, logging, etc. It consists of thick walled glass capillary. One end of it has a thin walled glass bulb filled with mercury or red colored alcohol. The air inside the capillary is removed and the other end is closed. The capillary is fitted inside a glass tube.

Clinical thermometer

Clinical thermometer

Showing the temperature of 37.7 °C (99.9 °F). A medical thermometer (also called clinical thermometer) is used for measuring human or animal body temperature. The normal temperature of human body is about 98.60F (370 C). Our body temperature cannot fall below 950 F or rise.

Differences between laboratory thermometer and clinical thermometer

Laboratory thermometerClinical thermometer
Used to measure the temperature in the laboratory.1. Used to measure the temperature of human body and animal body
Range of temperature is from – 300 C to 1100 C.2. Range of temperature is from 950 F to 1080 F. (35o C to 42.2o C)
Constriction is absent. 3. Constriction is present.

Now a days many other advanced types of thermometers are used. For example, digital thermometer, constant volume gas thermometer, platinum resistance thermometer, thermo electric thermometer etc.

Exercises

Fill in the blanks with suitable words

1.The primary source of heat is  Sun

2. In hot water the movement of molecules is Faster

3. Temperature is measured by Thermometer.

4. The S.I unit of heat is Joule (J).

5. The S.I unit of temperature is Kelvin (k)

II. Answer the following questions

1.Write the differences between heat and temperature.

Heat Temperature
1. Heat is a form of energy.Temperature is the measure of degree of hotness.
2. S.I. Unit of heat J (joule)S.I. Unit of temperature is K (kelvin).
3. The sum of kinetic energy of all the molecules in a matter.The average kinetic energy of the molecules.

2.Draw a neat labeled diagram of a laboratory thermometer.

3. Draw a neat labeled diagram of a clinical thermometer.

4.Write the differences between a laboratory thermometer and clinical thermometer.

Laboratory thermometerClinical thermometer
Used to measure the temperature in the laboratory.Used to measure the temperature of human body and animal body
Range of temperature is from – 300 C to 1100 C. Range of temperature is from 950 F to 1080 F. (35o C to 42.2o C)
Constriction is absent.Constriction is present.

3.Heat transfers from a hot body to a cold body. Give an illustration.

It is possible of course to make a cool object in a warm place cooler this is what a refrigerator does but this involves the input of some external energy.  As such the flow of heat is not spontaneous.

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