All three techniques can be used to separate a liquid from a solid. QUESTION: Which technique is best used to separate pure water from saltwater? A. filtration, B. evaporation, C. distillation All three techniques can be used to separate a liquid from a solid. Filtration works if the solid is not dissolved in the liquid. The mixture can be 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. Distillation involves evaporation, followed by condensation of the gas back to a liquid. SCRIPT: Which technique is best used to separate pure water from saltwater? A. filtration, B. evaporation, C. distillation PAUSE CLICK All three techniques can be used to separate a liquid and a solid. Filtration only works if the solid is not dissolved in the liquid. The mixture can be run through a porous filter paper, which will trap the solid (the “residue”), and let the liquid pass through (the “filtrate”). Filtration will not work in this case because the salt is dissolved in water. Evaporation involves heating the mixture makes the liquid turn to a gas which leaves behind the solid. This will work but you won’t be able to recover the water. Distillation involves evaporation, followed by condensation of the gas back to a liquid. This is the best technique to use. CONTINUED ON NEXT SLIDE

Filtration set up Filter Funnel Filter paper (white), traps solid (“residue”) 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. The mixture to be separated is poured into the funnel. The paper traps the solid, which is called the residue. CLICK CLICK The liquid, called the filtrate, passes through the paper and is collected in a beaker. This is essentially the same technique used in a coffee maker. CONTINUED ON NEXT SLIDE Beaker, collects liquid which passed through the funnel (the “filtrate”)

Evaporation Evaporating dish Burner flame Here’s a typical laboratory set up for separating a mixture by evaporation. CLICK CLICK The mixture is placed in a porcelain evaporating dish. The mixture is then heated. The liquid turns into a gas and the solid is left behind in the evaporating dish. Burner flame

Distillation set up Here’s a a typical laboratory set up for distillation. A mixture is placed in a flask. HIGHLIGHT flask As the mixture is heated, the liquid turns into a gas, which rises and is guided into a condenser. HIGHLIGHT condenser. The condenser is just a tube that is jacketed with an larger tube. Water flows through the outer tube to keep the inner tube cool. As the gas comes in contact with the cool tube, it condenses back to a liquid. The liquid is collected as it exits the condenser. The distilled liquid is also called the distillate. CALLOUT “distillate” CLICK PAUSE END RECORDING

Video ID: 1-3-1 © 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