When hot tea or milk is taken in a saucer, its surface area is increased. Since, evaporation is a surface phenomenon. The rate of evaporation becomes faster with the increase in surface area. Tea or milk cools down faster in a saucer making it easier for a sip. On the other hand, when hot tea or milk is taken in a cup, surface area is comparatively small due to the narrow shape of the cup. Small surface area slows down the process of evaporation. Hence, tea or milk takes long time to cool in a cup which makes it difficult to take a sip.