Heat

We often do it by touching the objects. But is our sense of touch reliable? 

Activity 

Take three small tubs/containers. Label them as A, B and C. Put cold water in mug A and hot water in mug B. Mix some cold and hot water in mug C. Now dip your left hand in mug A and the right hand in mug B. After keeping the hands in the two mugs for 2–3 minutes, put both the hands simultaneously in mug C (Fig). Do both the hands get the same feeling?  

 Left hand tells that the water in mug C is hot and the right hand tells that the same water is cold. This shows that we cannot always rely on our sense of touch to decide whether an object is hot or cold. Sometimes it may deceive us.  Then, how do we find out how hot an object really is? 

A reliable measure of the hotness of an object is its temperature. 

Or 

Temperature is a measure of the degree of hotness of an object. 

Thermometer is a device used for measuring temperature.