A Soluble Separation Solution
AbstractHave you ever mixed together salt and sand? It is fun to see how all of those tiny grains of salt and sand mix together! But what if you had to separate them out again? Do you have nightmares of tiny tweezers, a magnifying glass, and hours spent picking grains of salt and sand apart? Do not be afraid, there is another way! In this chemistry science project you will use the differences in solubility between salt and sand to find out the simple "solution" to this problem.
Sara Agee, Ph.D., Science Buddies
Teisha Rowland, Ph.D., Science Buddies
Make a mixture of sand and salt and use the difference in their solubility to separate them.
Chemistry is the study of matter and how matter behaves and interacts with other kinds of matter. The way that matter behaves is called a property of matter. Everything around us is made of matter, and you can explore the properties of matter using some common chemicals around your home.
One important property of matter is called solubility. We think about solubility when we dissolve something in water. If a chemical is soluble in water, then the chemical will dissolve, or disappear, when you add it to water. If it is not soluble, or insoluble, then it will not dissolve and you will still see it floating around in the water or at the bottom of the container.
When you dissolve a soluble chemical in water you are making a solution, and solutions are very important for chemistry. In a solution, the chemical you add is called the solute and the liquid that the chemical dissolves in is called the solvent. Even though when a solvent dissolves a solute it becomes invisible, the solute is still there. If you were to evaporate all of the liquid away from the solution, you would be left with your dry chemical again. In fact, this is how salt is processed in giant salt flats where seawater is slowly evaporated, leaving behind huge amounts of sea salt.
All of the different kinds of matter can be sorted into categories based upon whether they are soluble or not in different solvents. Because of this, the properties and solubility of different chemicals can be used to separate mixtures of chemicals. A chemical mixture is a blend of two or more different kinds of chemicals where the individual chemicals do not react with each other, but remain separate. You can see an example of this when you look closely at a dry mixture of salt and sand.
In this chemistry science project, you will use the different properties of the chemicals in salt and sand to separate a mixture of the two. By doing this, you will learn about the solubility of soluble and insoluble chemicals.
Terms and Concepts
Materials and Equipment
- Optional: Strainer
- Salt (60 mL)
- Sand (60 mL)
- Magnifying glass
- Glass canning jars with lids (2). Note: The jars need to hold at least 8 oz. and withstand being safely heated to 325° F.
- Graduated cylinder (100 mL volume) or measuring cup. A graduated cylinder is available online at Amazon.com.
- Teakettle or pot
- Spoons (2)
- Coffee filter
- Oven mitts
- Lab notebook
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- Before you begin, examine your salt and sand closely and make some initial observations. You can place some salt and sand on a napkin or piece of paper and, using your magnifying glass, make some observations and draw what you see. What do you notice? In your lab notebook, make a data table like Table 1 and record your observations in it, in the "Observations before mixing" row.
- Note: If your sand has a lot of debris in it, use a strainer to purify it and make your observations again.
|Observations before mixing|
|Observations of the mixture|
|Observations after adding water|
|Observations after separation|
|Observations after drying|
- In one of your glass canning jars, add 60 milliliters (mL) (or 1/4 cup) of salt, and 60 mL of coarse sand.
- Put the lid on your jar and shake until the salt and sand are completely mixed together.
- Using your magnifying glass, look closely at the mixture. What do you notice? Can you still see the individual grains of salt and sand? Record your observations in the data table in your lab notebook, in the "Observations of the mixture" row.
- Put the teakettle or pot on the stove, and heat up some boiling water. Have an adult help you do this.
- Have an adult help you carefully pour 120 mL (or 1/2 cup) of boiling water into your jar. Be careful as the glass will get very hot! Carefully stir the jar with a spoon.
- Using your magnifying glass, look closely at your solution. What do you notice? Can you still see the individual grains of salt and sand? Record your observations in your data table, in the "Observations after adding water" row.
- Place the coffee filter in the funnel and place the funnel in the top of your second glass canning jar to make your separation apparatus, as shown in Figure 1.
- Slowly pour the solution over your filter, being careful not to pour too much at once. As the solution seeps through the filter, let it collect in your jar.
- Now looking at the coffee filter, what do you see? Record your observations in your data table, in the "Observations after separation" row. Carefully scrape off any particles on the filter with a spoon and place them into the first glass jar.
- Place both glass jars onto a cookie sheet, and have an adult help you bake the jars on the cookie sheet in the oven at 325° Fahrenheit (F) until all of the water has evaporated from both of the jars. This may take over an hour.
- Turn off the oven and let it cool down for at least 1 hour.
- Safety Note: If glass undergoes a rapid temperature change, it may break or shatter. For this reason, it is important that you let the oven cool down for at least an hour before taking out the jars.
- After the oven has cooled down, have an adult help you carefully remove the jars, using oven mitts, and allow them to cool to room temperature before handling. They will probably still be very hot!
- After the jars are cool, use your magnifying glass to make observations of the two jars. What do you notice? Can you still see the individual grains of salt and sand? Are they mixed together or separated? Record your observations in your data table, in the "Observations after drying" row.
- Now carefully use the graduated cylinder or measuring cup to measure the amount of salt and sand you ended up with. Do these amounts match the amounts you started with? (Hint: See step 2.) Why do you think this happened?
- Tip: If you use the graduated cylinder to do this, you may want to use the funnel (without the filter) to help pour the salt and sand grains into the graduated cylinder.
Ask an Expert
- Many different chemicals have different solubilities. By adding different amounts of salt, sugar, or baking soda to water you can see how soluble each chemical is. Just add each chemical a teaspoon at a time to a glass of water until you notice that it no longer dissolves when you stir it around. Be sure to use the same amount of water for each experiment! The chemical that dissolves the most into the same amount of water is the most soluble, and the chemical that dissolves that least is the least soluble. Try it!
- How might temperature affect the solubility of a chemical? Try dissolving the same amount of sugar in hot water, room temperature water, and ice-cold water. What happens? Can you think of other variables that might affect solubility?
- Salt, sugar, and other substances can be soluble in one liquid (or solvent) but insoluble in a different liquid. Try dissolving salt in different liquids to find out what it is soluble in, and what it is insoluble in. For example, you could try dissolving salt in water, vegetable oil, or another liquid. (Be sure to use the same amount of salt and liquid each time.) Is salt soluble in some of these liquids, but insoluble in others? You could try other substances too, like sugar, and compare their solubility in the different liquids.
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