This could provide a stimulus for further investigations looking at how to separate other mixtures of solids, either of different particle sizes or by solubility. Similarly, it may be difficult to source the equipment needed to evaporate water to recover the dissolved salt. Head stands and tea lights can work well as possible alternatives.
When carrying out this activity be aware that some insoluble solids are able to form suspensions. This is where the particles appear to have dissolved, when in fact they have been spread out throughout the liquid. A good indicator that a suspension has formed is that the liquid will go cloudy or the particles can be heard scraping as the mixture is stirred.
The layout of this activity is very prescriptive as the procedure is set out on a step by step basis. This collection of over practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures.
Connect your curriculum teaching on chemical changes to engaging sustainability contexts. This topic web suggests classroom activities linked to plastic degradation and clean cooking. Use this practical to investigate how solutions of the halogens inhibit the growth of bacteria and which is most effective. Site powered by Webvision Cloud. Skip to main content Skip to navigation. Four out of five 2 comments. Procedure Pour the sand—salt mixture into the beaker so that it just covers the base.
Add about 50 cm 3 of water, or add water until the beaker is about one-fifth full. As the water evaporates, the salt will remain behind. You can speed up the process by raising the temperature or by blowing dry air over the surface of the liquid. A variation of this method is to pour the salt water onto a piece of dark construction paper or a coffee filter.
This makes recovering the salt crystals easier than scraping them out of the pan. Another way to separate salt from water is to use reverse osmosis. In this process, water is forced through a permeable filter, causing the concentration of salt to increase as the water is pushed out.
While this method is effective, reverse osmosis pumps are relatively expensive. However, they can be used to purify water at home or when camping.
Electrodialysis can be used to purify water. Here, a negatively-charged anode and a positively-charged cathode are placed in water and separated by a porous membrane. When an electric current is applied, the anode and cathode attract the positive sodium ions and negative chlorine ions, leaving behind the purified water. Note: this process does not necessarily make the water safe to drink, since uncharged contaminants may remain.
A chemical method of separating salt and water involves adding decanoic acid to salt water. The solution is heated. Upon cooling, salt precipitates out of the solution, falling to the bottom of the container.
What happens to the salt? Does it dissolve in the water? Put on the lid and shake the cup for about 20 to 30 seconds.
What does the mixture look like? Repeat the previous two steps using cup 2 with rubbing alcohol. What happens to the salt this time? Does the mixture look different from the water—salt mixture? Take the cap off the permanent marker and swirl its tip in the water in cup 3 for about 10 seconds. Put the lid on the cup and shake it for five seconds.
Does the ink dissolve in the water? What does the solution look like after shaking? Repeat the previous step with cup 4 rubbing alcohol. Does the resulting mixture look different? If so, what is different? Can you explain the differences? Next, pour the alcohol from cup 4 into the water in cup 3. Put the lid back on and swirl the mixture for five seconds.
Does the rubbing alcohol mix with the water? What happens to the color of the mixture? Do you see separate layers forming? Now, add one teaspoon of salt to the mixture in cup 3. Put the lid on the cup and shake it for 20 to 30 seconds. What happens when you add the salt to the mixture?
Does the mixture look different before and after shaking? Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter.
Updated January 25, Separating Sand and Salt Students are often asked to separate salt and sand to learn about mixtures and to explore the differences between forms of matter that can be used to separate mixture components. Three methods used to separate salt and sand are physical separation picking out pieces or using density to shake sand to the top , dissolving the salt in water, or melting the salt.
Probably the easiest method to separate the two substances is to dissolve salt in water, pour the liquid away from the sand, and then evaporate the water to recover the salt. Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. How to Separate Salt and Sand — 3 Methods. Properties of Ionic and Covalent Compounds. Chemistry Scavenger Hunt Clues and Answers.
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