Why is it necessary to wait until the next mixture returns to room temperature before weighing it?

Question

had you weighed the mixture while it was still warm,would its observed mass be too high or too low?explain....

Answer 1

You have to wait for it to be room temperature because temperature greatly affects a matter's mass, density and volume relatively.

If it's warm, usually, the density and the mass all get lower. When it's cold, it gets denser and heavier.

The molecules of warm or heated objects get excited, and therefore spread out more. This makes the matter less dense. When it is colder, the molecules compress more, making the matter dense.

Answer 2

The warmer the mixture, the more it will weigh so the observed mass would be too high.  To get a correct analysis you must always re-weigh at the same temperture that it was originally weighed because good "scientific method" means that all variables (except the one you are testing) are controlled.

Answer 3

The mass of the sample will remain constant however the volume will depend upon its temperature because most materials expand with an increase in temperature.  Unless weighed in a vacuum, air surrounding the sample will affects its measured weight (slightly) because of buoyancy.  If all measurements are take at room temperature the affects of buoyancy will cancel (or can be accounted for in very accurate measurements).  If the sample is greater than room temperature it may also create an updraft of warmed air that might affect a very accurate measurement of weight on sensitive laboratory balances, etc.