The solute food coloring is dissolved in the solvent water when the molecules of the solute are so thoroughly intermixed within the molecules of the solvent that they do not settle out or separate. This demonstration showed that food coloring can dissolve in water. Describe an experiment you could do to compare how isopropyl alcohol, mineral oil, and corn syrup dissolve in water.
Students should agree that they will need three cups filled with the same amount of water. Give each student an activity sheet.
Explore Have students conduct an activity to see how well isopropyl alcohol, mineral oil, and corn syrup dissolve in water.
Question to Investigate Do isopropyl alcohol, mineral oil, and corn syrup dissolve in water? Pour about 1 tablespoon of isopropyl alcohol, mineral oil, and corn syrup into their labeled cups. Pour water into all three labeled cups until each is about half-full.
While looking at the water from the side, slowly pour the alcohol into its labeled cup. Without stirring, watch to see if the alcohol dissolves in the water on its own. Record your observations in the chart. After waiting about 10 seconds, stir to see if the alcohol dissolves. Record your observations. Repeat Steps 2—5 for oil and corn syrup. Expected Results The alcohol looks kind of gray and swirly as it goes into the water. The alcohol tends to stay on the surface of the water because it is less dense than water.
It does not seem to dissolve immediately but dissolves when stirred. The oil stays on the surface of the water because it is less dense than water but it does not appear to mix much at all with the water. When stirred, the oil breaks apart a bit and then forms a layer again on the surface of the water.
The oil does not dissolve. The corn syrup sinks in the water because it is more dense than water. It seems to stay there without much initial dissolving. After stirring, the corn syrup dissolves into the water and the solution turns clear. Discuss student observations. Ask students: Can a liquid dissolve another liquid? Students should realize that some liquids, but not all, can dissolve in water. Based on your observations of the way isopropyl alcohol, mineral oil, and corn syrup dissolve in water, would you say that solubility is a characteristic property of a liquid?
Solubility is a characteristic property because each liquid interacted with the water differently. Explain Discuss how the molecular structure of isopropyl alcohol, mineral oil, and glucose in corn syrup determines whether or not each liquid will dissolve in water. Point out the bond between oxygen and hydrogen in one area of the alcohol molecule. Ask students: What do you already know about the O—H bond? It is polar. The oxygen has a slight negative charge, and the hydrogen has a slight positive charge.
Shishin , A. Voskov , I. Russian Journal of Physical Chemistry A , 84 10 , Iliuta , Peter Rasmussen. Extended UNIQUAC model for correlation and prediction of vapor—liquid—liquid—solid equilibria in aqueous salt systems containing non-electrolytes. Part B. Alcohol ethanol, propanols, butanols —water—salt systems. Chemical Engineering Science , 59 17 , Liebigs Annalen , 6 , Cowie , Mahmood A. Mohsin , Iain J. Alcohol-water cosolvent systems for poly methyl methacrylate.
Polymer , 28 9 , Mikhailov , E. The structure and thermodynamics of aqueous solutions of alcohols in the range of high alcohol concentrations.
Journal of Structural Chemistry , 16 3 , Frenkel , X. Hong , R. Wilhoit , K. 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? If so, how does it look different?
Can you explain your results? What color is the mixture? Extra: Can you separate other liquid mixtures using salt? What about ethanol and water or acetone and water?
Try different liquid mixtures to find out! Extra: Are there any other salts—for example potassium chloride, a salt substitute, or Epsom salt—that you could use to separate liquids? Repeat the test, but this time use a different salt than table salt. Do you still see the same results? If not—how are your results different? Extra: How much salt do you need to separate the rubbing alcohol and the water? Find out by varying the amounts of salt that you add to the rubbing alcohol and water mixture.
Build a Cooler. Why are organic compounds important? How are compounds in organic chemistry named? What is the general formula of a carboxylic acid? What is a carboxyl group? What is an alkane?
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