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• The hotness or coldness can be identified by touching the object. E.g. If we touch the cup containing tea then it appears hot, but if we touch an ice piece then it appears cold.
• The measure of hotness or coldness of an object is called its temperature.
• Temperature is measured by a device called thermometer.
• Clinical thermometer – Measures temperature of the body.
• Structure of clinical thermometer
  • It is a long narrow tube with same thickness throughout the length.
  • One side of this tube there is a bulb which contain mercury
  • For reading the temperature there is a scale printed on thermometer
  • The clinical thermometer has reading from 35 °C to 42 °C.
  • There is very fine tube which originate from the bulb, it is called capillary tube.
  • With rise in temperature, mercury expand in this tube. The capillary tube is bent near the bulb. It prevents mercury from flowing back into the bulb immediately.
  • To get more correct reading there are some divisions between two consecutive numbers. If there are 10 divisions then each division signifies 1/10 = 0.1 °C temperature and if there are five divisions then each division suggests ⅕ = 0.2 °C temperature.
• Structure of laboratory thermometer
  • Measuring the temperature of other objects we use laboratory thermometer
  • There is a bulb at a side of the thermometer.
  • A narrow tube having same thickness throughout originates from the bulb and extend towards the highest reading.
  • A tube formed by this bore is the capillary tube.
  • Generally the laboratory thermometer have scale between -10 °C to 110 °C. There are 10 divisions between each consecutive numbers that means each division indicates 1 °C.
  • There is no bend in laboratory thermometer
• Heat transfer takes place from conduction, convection and radiation.
• Conduction of heat – heat is transferred from hot region to cold region
• Convection of heat – heat transfer by actual motion of the medium is called Convection. In case of forced heat transfer, convection is called forced convection. If the convection takes place naturally then the convection is called natural or free convection.
• Radiation – Heat transfer takes place with out material medium
• Watch complete video on conduction convection and radiation here