Chemistry/Science help needed here!?

Question

So I just did an experiment at school today. I took 10 mL of water and 10 mL of alcohol and put them both in a test tube. I noticed that when they both combined it was only 18.5 mL and not 20. interesting, yea?and I noticed that the test tube got a little warmer when I touched it and little tiny "liquid" bubbles were in the test tube now.can anyone give me a detailed explanation as to why liquid bubbles form anyway? this experiment/solution was not boiling water so that can't be the solution.so why then just by simply adding some water and some alcohol in a test tube, some liquid tiny particle bubbles form? please and thanks in advance.I'm really curious.

thanks all of you! and greatly appreciate it Aldo. Thanks SO much! I understand it all very good now (:

Answer 1

I am glad that you are very observant. That is what experiments are for - intrigues you to ask more questions.

Anyway, one property of some liquids, which is not apparent, and sounds contrary to common sense is that their volumes are NOT ALWAYS additive. it may be less, equal or more than the individual volumes. It all depends on the chemistry and nature of interactions of the liquids being mixed.

In case of alcohol and water, the is so much hydrogen bonding and other interactions that the volumes are not additive. I think, so far, there is not a formula yet to actually predict the behaviour of mixing to liquids. Data and additional info on the actual behaviour just has to come from empirical data.
Sure, we can make conjectures, but in this field, empirical data is it at this time.

The fact that you see bubbles is very simple. Your body and hand temperature is about 98.6 F. This is enough energy to make little "cells" where some alcohol can evaporate. Note that your test tube is open to atmosphere. And note also that water will boil when the vapor above it is equal to the outside pressure.

Or, putting it differently. When you place a drop of alcohol on top of a glass, the alcohol will eventually be gone and yet the room temperature is about 25 C and the boiling point of alcohol is about 78 C! At any temperature, all liquids will have some vapor pressure and when the pressure equals the outside pressure it is only then that the liquid will boil. At all temperatures, it is slowly evaporating like what happened in your experiment. Now, if you tightly close ( no longer open to atmosphere) the test tube, you will be hard pressed to find any bubbles just by touching the tube.

Answer 2

The mass for chemical reactions is conserved. (the total mass of products equals the total mass
of reactants.).

but the volume of mixing two (or more) substances together is not conserved.

In the case of ethanol (alcohol) and water, the final volume is less than the sum of the components' volume. Liquid water has a more open structure that is broken up by the addition of ethanol so the mixture "collapses".

Answer 3

alcohol and the oygen and hydrogen atoms of the water can create a reaction in the liquid.

and the reason you got 18.6 mL instead of 20 mL was because some of the liquid was lost in transaction. Some of it still stayed in the other tubes.