Temperature - Sub Topics

  • What is Temperature?
  • Temperature Measurement Units
  • What is a Thermometer?
  • How to Read a Thermometer?
  • Solved Questions on Temperature
  • In this chapter, we shall explore the world of temperature, look into how we measure it and find out how it affects our lives every day. Temperature is a concept that helps us figure out how hot or cold something is. We see temperature changes in the different seasons.

    What is Temperature?

    Temperature is a measure of how hot or cold something is. It is represented by the letter 'T'.

    Temperature helps us determine if something is hot or cold. When we touch something warm, we say it is hot and when it feels cool, we call it cold. That is why in the winter, we like to have hot coffee and in the summer, we enjoy cold drinks.

    Things that feel very warm are called hot objects and they have higher temperatures. Examples of hot objects include fire, tea, coffee, etc.


    Things that feel cool are called cold objects and they have lower temperatures. Examples of cold objects include ice cream, cold/iced coffee, cold drinks, etc.


    Temperature Measurement Units

    The Units of temperature are:

    1. Celsius (°C) 
    2. Fahrenheit (°F)
    3. Kelvin (K)

    The symbol (°) is known as the degree symbol which is frequently used in temperature measurement to indicate degrees on different temperature scales in Celsius (°C) and Fahrenheit (°F).

    Example: The temperature in Rome is recorded as 26°C. If the temperature in Rome is 17°C lower than that in Dubai, what is the temperature in Dubai?


    a) 33°C
    b) 43°C
    c) 53°C
    d) 63°C

    Answer: b) 43°C

    Explanation: The temperature in Rome is recorded as 26°C.
    If the temperature of Rome is 17°C lower than the temperature of Dubai, then the temperature of Dubai is 17°C higher than the temperature of Rome.
    Temperature in Dubai = 26 + 17 
                                    = 43°C

    Temperature Measuring Devices

    A thermometer is an instrument used to measure temperatures. It consists of a narrow and sealed glass tube containing a liquid (mercury).

    Modern thermometers use digital technology for temperature measurement.


    The labelled diagram of the thermometer is shown below:


    How to Read a Thermometer?

    It typically consists of a narrow, sealed glass tube containing a liquid (such as mercury) that expands or contracts with temperature changes, allowing the temperature to be read on a scale. The increase and decrease in the level of liquid mercury (indicated by the red markings) indicate changes in temperature.

    → The temperature at which water freezes is indicated by the thermometer and is expressed as 0 degrees Celsius (0°C).


    → The temperature at which water boils is indicated by the thermometer and is expressed as 100 degrees Celsius (100°C).


    Example: Fill in the blank:

    Water boils at ________ °C and freezes at ________ °C.

    a) 0°C, 100°C 
    b) 0°C, 90°C 
    c) 100°C, 0°C 
    d) 100°C, 1°C 

    Answer: c) 100°C, 0°C 

    Explanation: Water boils at 100°C and freezes at 0°C.

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