4. Heat and temperature
Heat is a form of energy that produces the sensation of warmth and flows from hot body to cold body. It is produced due to the vibration of molecules. When molecules vibrate faster more heat is produced.
Matter is made up of molecules, these molecules contains energy. When substances are heated, molecules vibrate that increases the kinetic energy of the molecules. In other words when heat is supplied to an object, it increases the amplitude and frequency of vibration of molecules. These vibrating molecules contain kinetic energy called heat energy. Molecules are vibrating rapidly if the body is at high temperature.
The SI unit of heat energy is Joule (J). In CGS system, it is measured in calorie. One calorie is the quantity of heat required to raise the temperature of 1g of water through 1°C.
Heat also can be defined as the sum of the kinetic energy that the molecules of an object possess is called the heat energy of the object. Quantity of heat energy present in an object depends upon mass and average kinetic energy of the molecules. Quantity of heat is directly proportional to the:
i. Average kinetic of molecules of the body.
ii. Mass of a body i.e the total number of molecules that a body contains.
Heat energy has great many applications. It is used for cooking food, propelling and running vehicles, proper amount of heat from sun provides suitable place for living being on earth etc.
Effects of heat:
i. Increase in volume: When an object is heated, its size and volume increases.
ii. Chant in state: On heating, a solid converts into liquid, while liquid converts into vapour.
iii. Rise in temperature: When a body is heated its temperature increases.
iv. Physical change: When a body is heated, physical properties like colour changes.
Temperature:
The temperature of a body is defined as the degree of hotness or coldness of a body or it can be defined as the average kinetic energy of molecules of the substance.
When two bodies at different temperature are placed in contact the heat flows from the body at higher temperature to the body at lower temperature. Temperature determines the direction of flow of heat energy from one body to another when these are in contact with each other. Thermometer is used to measure the temperature of an object.
Heat is a form of energy that produces the sensation of warmth and flows from hot body to cold body. It is produced due to the vibration of molecules. When molecules vibrate faster more heat is produced.
Matter is made up of molecules, these molecules contains energy. When substances are heated, molecules vibrate that increases the kinetic energy of the molecules. In other words when heat is supplied to an object, it increases the amplitude and frequency of vibration of molecules. These vibrating molecules contain kinetic energy called heat energy. Molecules are vibrating rapidly if the body is at high temperature.
The SI unit of heat energy is Joule (J). In CGS system, it is measured in calorie. One calorie is the quantity of heat required to raise the temperature of 1g of water through 1°C.
Heat also can be defined as the sum of the kinetic energy that the molecules of an object possess is called the heat energy of the object. Quantity of heat energy present in an object depends upon mass and average kinetic energy of the molecules. Quantity of heat is directly proportional to the:
i. Average kinetic of molecules of the body.
ii. Mass of a body i.e the total number of molecules that a body contains.
Heat energy has great many applications. It is used for cooking food, propelling and running vehicles, proper amount of heat from sun provides suitable place for living being on earth etc.
Effects of heat:
i. Increase in volume: When an object is heated, its size and volume increases.
ii. Chant in state: On heating, a solid converts into liquid, while liquid converts into vapour.
iii. Rise in temperature: When a body is heated its temperature increases.
iv. Physical change: When a body is heated, physical properties like colour changes.
Temperature:
The temperature of a body is defined as the degree of hotness or coldness of a body or it can be defined as the average kinetic energy of molecules of the substance.
When two bodies at different temperature are placed in contact the heat flows from the body at higher temperature to the body at lower temperature. Temperature determines the direction of flow of heat energy from one body to another when these are in contact with each other. Thermometer is used to measure the temperature of an object.
Thermometer:
The instrument that is used to measure the temperature is called thermometer and the branch of science related to measurement of temperature of a body is called thermometery. There are different types of thermometer, they are liquid thermometer, gas thermometer, resistance thermometer, radiation thermometer, vapour thermometer etc.
Liquid thermometer are based on the principle of change in volume of a liquid with change in temperature. Mercury and alcohol thermometers are based on this principle.
Differences between heat and temperature:
|
S.no |
Heat |
Temperature |
|
1 |
Heat is a form of energy which gives us the sensation of warmth. |
It is the degree of hotness or coldness of a body. |
|
2 |
It is measured in calorie or joule. |
It is measured in °C, K etc. |
|
3 |
Heat flows from a body at higher temperature to a body at lower temperature. |
The temperature of two bodies gives the direction of flow of heat. |
|
4 |
It is the total KE of all the molecules of a substance. |
It is the average KE of the molecules. |
|
5. |
It is measured by Calorimeter. |
It is measured by the thermometer. |
|
6. |
It is cause of temperature. |
It is effect of heat. |
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