Heat
Science Class Seven
Summary & Important terms: heat
(1) Heat is a type of energy
(2) Heat is measured in temperature
(3) Thermometer is a device which is used to measure temperature
(4) The unit of temperature is Celsius, Fahrenheit, and Kelvin, etc.
(5) There are different types of thermometer. These are clinical thermometer, laboratory thermometer, digital thermometer, infrared thermometer.
(6) Different types of thermometer is used for different purposes.
(7) Mercury is used in clinical thermometer.
(8) Clinical thermometer is used to measure body temperature.
(9) Clinical thermometer is generally calibrated from 35oC to 108oC.
(10) Laboratory thermometer is generally calibrated from –10oC to 110oC.
(11) Heat travels from one place to other place by transfer.
(12) Heat is transferred by three processes. These processes are conduction, convection, and radiation.
(13) In solids, heat is transferred by the process of conduction.
(14) In liquids, heat is transferred by the process of convection.
(15) From sun to earth heat is transferred by the process of radiation.
(16) The process of radiation to transfer of heat does not require any medium.
(17) A hot body transmits heat by the process of radiation.
(18) Sea breeze: The colder breeze blows from sea surface to land surface in summer is called sea breeze. This happens because of uneven heating of land surface and water surface.
(19) Land breeze: The hotter breeze blows from sea surface to the land surface in winter is called land breeze. This happens usually in the winter season and in the night time.
(20) Objects having dark surface absorbs more heat than objects having light coloured surface.
(21) In summer people prefers to wear light coloured clothes. Because light coloured cloths reflects most of the heat falls upon them.
(22) In the winter season people prefers to wear dark coloured clothes. Because dark coloured cloths absorbs most of the heat and keep people who wear them warm.
(23) In winter season people wears woollen clothes. Woollen clothes are thick and more pores. Air bubbles get trapped in pores of woollen clothes and act as insulator. This keeps people warm who wear woollen clothes in winter.
Important Terms related to Chapter Heat Class seven Science
(1) Heat : Heat is a type of energy.
(2) Thermometer : Thermometer is a device which is used in measuring of temperature.
(3) Celsius scale : Celsius is a type of unit which is used in measuring of temperature. Celsius scale is also known as Centigrade scale.
Anders Celsius, a Swedish Astronomer suggested the "Centigrade" scale to measure the temperature in 1742. Later on in his honour the scale for measuring of temperature named as "Celsius".
(4) Fahrenheit : Fahrenheit is another scale used in measuring of temperature.
Daniel Gabriel Fahrenheit invented the first mercury based thermometer in the year of 1714, in which he used mercury to measure the temperature. Daniel Gabriel Fahrenheit was a Dutch scientist. In the honour of his name, the unit of temperature coined as "Fahrenheit".
(5) Kelvin : Kelvin is another scale which is also used in measuring of temperature. It has been coined on the name of Lord Kelvin whose original name was William Thomson, who was a British mathematician.
(6) Conductor : Objects that allow heat and electricity to pass through them are called conductors. Example: Iron, copper, gold, silver, aluminium, etc. All metals are good conductor of heat and electricity. This is the cause that cooking utensils and electric wires are made of metal.
(7) Insulator : Objects that do not allow heat and electricity to pass through them are called insulators. Insulators are known as bad conductors also. Example: rubber, plastic, wood, etc. All non-metals are bad conductors of heat and electricity. This is the cause that handles of cooking utensils are made of wood or plastic, and covering of electric wires are made of rubber or plastic. Electric switches are also made of plastic.
(8) Conduction : Conduction is a process of transfer of heat. In solids heat is transferred by the process of conduction.
(9) Convection : Convection is a process of transfer of heat. In liquids heat is transferred by the process of convection.
(10) Radiation : A process of transfer of heat by which heat reaches to earth is called radiation. The process of radiation does not require any medium. All hot bodies transmit heat by the process of radiation.
(11) Land Breeze: The air blows from land surface towards sea surface is called land breeze. This happens because of uneven heating of land surface and sea surface.
(12) Sea Breeze: The air blows from sea surface to land surface is called sea breeze. This happens because of uneven heating of land and sea surface. In summer land absorbs heat faster than sea surface (large water surface). Because of this air just above the land surface gets heat and rises up creating a gap. To fulfil this gap colder air above the sea surface rushes towards land surface leaving a gap over the sea surface. The hotter air from land surface rushes to take the gap above the sea surface. This cycle continues and a colder breeze from sea surface to land surface starts blowing.
Conversion of Kelvin to Celsius and Celsius to Kelvin
Formula to convert Kelvin to Celsius
Kelvin is denoted by letter "K" and Celsius is denoted by the letter "C".
Celsius (C) = Kelvin (K) – 273
Or, C = K – 273
Question (1) Convert 100 K into Celsius
We know that,
Celsius (C) = Kelvin (K) – 273
Thus, C = 100 K – 273
⇒ C = –173o
Thus, 100 K = –173oC Answer
Question (2) Convert 500 K into Celsius
We know that,
Celsius (C) = Kelvin (K) – 273
Thus, C = 500 K – 273
⇒ C = –227o
Thus, 500 K = –227oC Answer
Formula to convert Celsius to Kelvin
Kelvin (K) = Celsius (C) + 273
Or, K = C + 273
Question (1) Convert 100oC to Kelvin (K)
We know that, Kelvin (K) = Celsius (C) + 273
Thus, K = 100oC + 273
⇒ K = 373
Thus, 100oC = 373 K Answer
Question (2) Convert 50o to Kelvin
We know that, Kelvin (K) = Celsius (C) + 273
Thus, K = 50oC + 273
⇒ K = 323
Thus, 50oC = 323 K Answer
Comparison of Celsius and Fahrenheit
Celsius is denoted by the letter "C" and Fahrenheit is denoted by the letter "F"
100oC = 212oF
The conversion from degree Celsius to Fahrenheit is slightly tricky. So you will learn it in upper classes.
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