New answers tagged

6

So it finally turned out to be an artefact, sorry. The probe was protected by a small metallic tube. Somehow water condensed inside. Since this water is isolated from the main liquid, it performed its own phase-transition releasing its latent heat right next to the sensor. The effect was not appreciated when freezing the probe alone. I don't know why, maybe ...


1

A nicely done experiment! Consider hand-warmers containing sodium acetate trihydrate, $\ce{NaCH3COO.3H2O}$. When heated above the melting point and then cooled, the compound does not quickly solidify, but can be greatly supercooled. Given an impetus to begin crystallization, such as the shock-wave produced by a "clicker" (or nucleation by a speck ...


2

But my source of confusion is that ambient pressure is not the only pressure pressing down on the liquid. Pressure does not press down. When something is under pressure, it exerts it in all directions. Maybe it would help imagining this problem in the absence of gravity (you would have to put the sample in a stretchy balloon to get some pressure while being ...


3

If you heat the commercial concentrated ammonia solution ($25$% $\ce{NH3}$) at usual pressure, it will boil at $32$°C and the vapor contains $3$% $\ce{H2O}$ (and of course $97$% $\ce{NH3}$). So the liquid looses much ammonia and nearly no water. Its total volume decreases a bit but the concentration of ammonia decreases more, so that it is necessary to heat ...


3

Certainly! The properties of individual atoms differ from the bulk material. Alkali metals (all metals, really) no longer have metallic behavior such as electrical conductivity when highly dispersed. As you surmise, these effects are studied at quite low pressure (you can observe individual atoms in the container!) and at temperatures approaching 0K. For ...


Top 50 recent answers are included