CHAPTER 25 – MEASUREMENTS Measuring temperature


Temperature is the measure of the hotness or coldness of an object or body. The practical unit of temperature is degrees Celsius (°C). A thermometer is the instrument used to measure temperature. There are many types of thermometers, but the most common are alcohol in glass and digital.


: Fig. 25.23 An alcohol thermometer


: Fig. 25.24 A digital thermometer Eureka


Handheld digital thermometers were used to check if someone had a fever before entering a building or event during the COVID-19 pandemic. While these instruments allow body temperature to be measured at a safe distance of one metre, they are not as accurate as other types of thermometers, as they measure external body temperature only.


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TEST TUBE


10. List three possible uses of a thermometer in everyday life. 11. What temperature in degrees Celsius is being measured on the thermometer shown in Fig. 25.25?


: Fig. 25.25 Error in measurement


In measurement, an error is a mistake that is introduced into a reading or an investigation.


Three types of error can happen when taking measurements:


• A blunder is a mistake caused by carelessness, e.g. spilling a liquid before measuring it.


• A systematic error is due to a problem with the measuring instrument or environment, e.g. a metre stick that is worn down at the end.


• A random error is a mistake made by the person taking the measurement, e.g. reading a scale incorrectly.


) Fig. 25.26 Ensure measuring instruments are in good condition


Elements of Science 247


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