The larger the volumetric flask, the easierit is for students to observe the difference in volume. (However, you can use whatever glassware is available.)Using volumetric flasks makes this a very quantitative demonstration.

This demonstration is best performed using 3 volumetric flasks, which provide a good opportunity to instructstudents in the purpose and use of volumetric flasks. The 2 different molecules pack closer together than in pure solution, resulting in a reduction of volume. Second, open spaces in the liquid are much less likely because the ethyl alcohol interferes with any temporary open structures that are similar tothose of solid water. First, between the water and ethyl alcohol is strong hydrogen bonding that draws the different molecules close together. When water and ethyl alcohol mix, several forces come into play.

The open structure of solidice is the reason ice floats in water.

Recent studies suggest that some regions of pure water may temporarily resemble the solid structure of ice, which has a very open structure to maximize hydrogen bonding. Bonding models for liquid water, although extensively studied, are still not fully understood. What caused the volume reduction, and what happened to the lost volume?īonding models for liquids are more difficult to predict due to their significant molecular motion andstrong intermolecular forces. No, if you mix 250 mL of water with 250 mL of ethyl alcohol, only about 480 mL of solution results. What happens when an equal volume of water and ethyl alcohol mix? Is the mass additive? Is the volume additive? The Law of Conservation of Mass dictates that the mass is conserved, but is there a Law of Conservation of Volume?

Demo on effects of solvents