D. extraction, evaporation, filtration QUESTION: What sequence of laboratory procedures can be used to separate salt from a sand-and-salt mixture? A. extraction, filtration, evaporation B. filtration, extraction, evaporation C. evaporation, filtration, extraction D. extraction, evaporation, filtration In filtration, a mixture of a solid and liquid is run through a filter paper, which will trap the solid, and let the liquid pass through. Evaporation involves heating the mixture, which turns the liquid turn into a gas which leaves behind the solid. Extraction is a technique that takes advantage of differences in solubility. Salt will dissolve in water, sand will not. First step: extract salt with water SCRIPT: What sequence of laboratory procedures can be used to separate salt from a sand-and-salt mixture? A. extraction, filtration, evaporation B. filtration, extraction, evaporation C. evaporation, filtration, extraction PAUSE CLICK In filtration, a mixture of a solid and liquid is run through a filter paper, which will trap the solid, and let the liquid pass through. Filtration will not work as a first step in this case since we have a mixture of two solids… sand and salt. CROSS OUT filtration in choice B. Evaporation involves heating the mixture, which turns the liquid turn into a gas which leaves behind the solid. Evaporation will not work as a first step in this case either since we do not have a liquid. CROSS OUT evaporation in choice C. The correct answer must be choice A. Extraction, followed by filtration, then evaporation. Extraction is a technique that takes advantage of differences in solubility. Salt will dissolve in water, sand will not. So the first thing we need to do is add water to our sand-and-salt mixture. This will extract the salt from the sand-and-salt mixture. CLICK CONTINUED ON NEXT SLIDE

Filtration set up Filter Funnel Filter paper (white), traps solid (“residue”) Then we do a filtration. Here’s a typical laboratory set up for filtration. CLICK CLICK A funnel is mounted on a ring stand. A piece of filter paper is folded to fit into the funnel. We pour our mixture into the funnel. The sand will be trapped in the paper. CLICK CLICK The water, which contains the dissolved salt, passes through the paper and is collected in a beaker. The salt-and-water mixture is called the filtrate. CONTINUED ON NEXT SLIDE Beaker, collects liquid which passed through the funnel (the “filtrate”)

Evaporation Evaporating dish Burner flame Finally, we put the salt-and-water mixture in an evaporating dish CLICK CLICK The mixture is then heated. Water turns into a gas and the salt is left behind in the evaporating dish. CONTINUED ON NEXT PAGE Burner flame

D. extraction, evaporation, filtration QUESTION: What sequence of laboratory procedures can be used to separate salt from a sand-and-salt mixture? A. extraction, filtration, evaporation B. filtration, extraction, evaporation C. evaporation, filtration, extraction D. extraction, evaporation, filtration Note that if we were do to evaporation after extraction, as in choice D, our residue will just get back the original sand and salt mixture. So the correct answer is A. First we extract, or selectively dissolve, the salt from the mixture using water. HIGHLIGHT extraction in choice A Then we filter the entire mixture HIGHLIGHT filtration in choice A to separate the sand from the salt-water mixture, which becomes our filtrate. Then we heat our filtrate in an evaporating dish HIGHLIGHT evaporation in choice A to remove the water and recover the salt. CLICK PAUSE END RECORDING

Video ID: 1-3-2 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08