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www.GOALias.blogspot.comIn addition to the precautions needed while reading a clinicalthermometer, the laboratory thermometer• should be kept upright not tilted. (Fig. 4.5)• bulb should be surrounded from all sides by the substance of which thetemperature is to be measured. The bulb should not touch the surface of thecontainer.Fig. 4.5 Measuring temperature of water withan laboratory thermometerNote the reading. This is the temperatureof water at that time.Compare the temperature of waterrecorded by each student in the class.Are there any variations in thereadings? Discuss the possible reasons.Let us try to answer this question.Activity 4.5Take some hot water in a beaker or amug. Dip the thermometer in water.Wait till the mercury thread becomessteady and note the temperature. Nowtake out the thermometer from water.Observe carefully what happens now.Do you notice that as soon as you takethe thermometer out of water, the levelof mercury begins to fall. This meansthat the temperature must be read whilethe thermometer is in water.You may recall that while taking yourown temperature, you have to take thethermometer out of your mouth to notethe reading. Can you then use thelaboratory thermometer to measure yourBoojho now understand whyclinical thermometer cannot beused to measure hightemperatures. But still wonderswhether a laboratory thermometercan be used to measure his bodytemperature.Boojho wonders why the levelof mercury should change atall when the bulb of thethermometer is brought in contactwith another object?HEAT3939