Question

If samples are dried in the oven and their mass is determined before reaching room temperature, will values be high, low or correct? Why?

Answer 1

Ans: The masses of the samples will be slightly higher than normal-if you're using a highly sensitive balance. As hot air rises from the sample, it creates updrafts which swirl around in the analytical balance creating pressure. This pressure is forced down upon the scale, which being a highly sensitive device, reads a slightly higher than normal mass.

2. The opposive will true if the sample is effloroscent. As materials cool they tend to absorb moisture so may weigh more at room temperature than at higher temperatures when the moisture is more completely removed.