Key ConceptsLiquids have characteristic properties based upon the molecules they space made of.The nature of liquids depend on the attractions the molecule of the liquid have actually for each other and for various other substances.Liquids can dissolve details other liquids, relying on the attractions between the molecules of both liquids. Polar liquids, like water, dissolve various other liquids which are polar or rather polar.Polar liquids, choose water, do not dissolve nonpolar liquids choose oil.
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Students will ar isopropyl alcohol, mineral oil, and corn syrup in water to watch if any of this liquids dissolve in water. Students will extend their expertise and definition of “dissolving” and also see the certain, yet not all, liquids have the right to dissolve in water.
Students will identify and control variables to aid design a solubility check for different liquids in water. Student will have the ability to explain, ~ above the molecule level, why specific liquids, however not all, will dissolve in water. Castle will also be maybe to define that the solubility of a fluid is a characteristic home of the liquid.
Download the student activity sheet, and distribute one per student once specified in the activity. The activity sheet will certainly serve as the “Evaluate” ingredient of every 5-E great plan.
Be certain you and also the student wear effectively fitting goggles. Isopropil alcohol is flammable. Store it far from flames or spark sources. Read and follow every warnings top top the label. Isopropil alcohol and also mineral oil have to be disposed of according to local regulations.
Materials because that the DemonstrationsClear plastic cupWaterFood coloring Straw or popsicle stickIsopropyl alcohol (70% or higher)2 identical 100-mL i graduated cylinders
Materials because that Each GroupWaterMineral oil isopropyl alcohol (70% or higher)Corn syrup3 clear plastic cups5 little cupsPermanent marker or masking tape and a pen because that labeling cups3 straws or popsicle pole (for stirring)Laminated index card or card spanned with wax file Blue water Yellow isopropil alcohol (70% or higher) 2 droppersToothpick or popsicle stick
Do a demonstration to introduce the idea that solids aren’t the only substances that have the right to dissolve-liquids can likewise dissolve in liquids.
Ask college student to make a prediction:Solids, prefer salt or sugar, have the right to dissolve in water. Do you think that liquids deserve to dissolve in water?
Question come Investigate
Does liquid food color dissolve in water?
Materials because that the DemonstrationClear plastic cupWaterFood coloringStraw or popsicle stick
Note: A comparable demonstration was conducted ago in chapter 1 as proof that molecules are in motion. Here, the demonstration is supplied to show the attraction in between water molecules and also the fluid coloring molecule that allows the color to dissolve in the water.
ProcedureHold increase a clear plastic cup or other clear container the room-temperature water. Include 1 or 2 drops of food color and permit the coloring come drift and also spread in the water a bit.Explore
Have students conduct an task to see just how well isopropyl alcohol, mineral oil, and also corn syrup dissolve in water.
Question come Investigate
Do isopropil alcohol, mineral oil, and also corn syrup dissolve in water?
Teacher ready for every GroupLabel 3 little cups Alcohol, Oil, and Syrup for each group. Pour around 1 tablespoon of isopropyl alcohol, mineral oil, and also corn syrup into their labeling cups.
Materials for Each GroupWaterIsopropyl alcohol (70% or higher) in small labeled cupMineral oil in tiny labeled cupCorn syrup in tiny labeled cup3 clean plastic cupsPermanent mite or masking tape and also a pen because that labeling cups3 straws or popsicle sticks for stirring
ProcedureLabel 3 clean plastic cups Alcohol, Oil, and also Syrup.Pour water into all three labeled cups till each is around half-full. While looking at the water from the side, slowly pour the alcohol right into its labeling cup.Without stirring, watch to watch if the alcohol dissolves in the water ~ above its own. Record your monitorings in the chart.After waiting around 10 seconds, line to view if the alcohol dissolves. Document your observations. Repeat actions 2–5 because that oil and also corn syrup.
Expected ResultsThe alcohol looks sort of gray and swirly together it goes into the water. The alcohol often tends to remain on the surface of the water due to the fact that it is less dense than water. It does not seem come dissolve automatically but dissolves when stirred. The oil remains on the surface of the water due to the fact that it is less dense than water yet it go not appear to mix much at all v the water. As soon as stirred, the oil breaks apart a bit and also then develops a class again top top the surface ar of the water. The oil does no dissolve. The corn syrup sinks in the water because it is more dense than water. It seems to remain there without lot initial dissolving. After ~ stirring, the corn syrup dissolves right into the water and the equipment turns clear.
Discuss student observations.
Have students describe what the alcohol, oil, and corn syrup looked favor in the water and whether or no they dissolved.
Ask students:Can a fluid dissolve an additional liquid? Students must realize that part liquids, but not all, deserve to dissolve in water. Based upon your monitorings of the method isopropyl alcohol, mineral oil, and corn syrup dissolve in water, would you say that solubility is a characteristic building of a liquid? Why?Yes. Solubility is a characteristic property due to the fact that each liquid connected with the water differently.Extend
Look more closely at the method water and alcohol mix.
Water and also alcohol do some pretty amazing things as soon as they mix. Call students that you fancy water blue and isopropyl alcohol yellow so that they have the right to see the mixing better.
Question to Investigate
What happens together drops that water and also alcohol combine?
Teacher readyEither laminate one index card for each team or sheathe an index card through a piece of wax paper and secure the wax record with tape.Place around cup water in 1 cupAdd 2 drops of blue food coloring to the water. Place ¼ cup isopropyl alcohol in one more cup. Add 2 fall of yellow shade food coloring come the alcohol.Label 2 little cups water and also alcohol because that each group. You may reuse the tiny cup labeling alcohol indigenous the activity in this lesson. Place around 1 tespoon of each colored liquid into its pair that labeled cups for each group.
Materials because that Each GroupWater (colored blue)Isopropyl alcohol (70% or higher and colored yellow)Laminated index map or card spanned with wax paper2 droppersToothpick or popsicle pole
ProcedureUse a dropper come place about 5 fall of blue water with each other to do 1 big drop on her index card.Use one more dropper to make a similar huge drop of yellow alcohol near to, but not touching, the blue drop.
Use a toothpick to drag the blue water toward the yellow alcohol till they touch. As soon as the autumn touch, elevator the toothpick away and do no stir.
The alcohol and water will type of “shake” or “jiggle” ideal at the area whereby they room mixing.
Discuss college student observations.
Ask students:What perform you observe once the fall of alcohol and drop of water combine? students will notice that the alcohol and also water seem to shake in ~ the area where they room mixing. As the liquids mix, the yellow and blue colors incorporate to make green.
Tell students that the mix of alcohol and also water is not fully understood top top the molecular level. One factor for the shaky appearance might be that alcohol is less dense than water so as it mixes v water, the density of the all at once liquid changes. Alcohol (which alone floats ~ above water) sinks together it mixes. Maybe lots of small “sinkings” do the mixing look shaky. It could be the the transforming density causes light to refract in different ways to reason the shaky look. Perhaps the alcohol interferes with water’s surface ar tension and also causes a shaky watch on the surface. It is likewise true that when water and alcohol room mixed, the equipment gets warmer. Possibly the heat increases molecular movement at the surface, which in which method contributes come the shaky look.
Do a show to show that once water and alcohol combine, the volume that the resulting solution is much less than expected.
Tell students the the characteristic means water and alcohol communicate with each other causes an additional interesting phenomenon.
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Materials because that the DemonstrationIsopropyl alcohol (90% or higher)Water2 the same 100-mL i graduated cylinders
ProcedureMeasure 50 mL of isopropyl alcohol and also pour it right into a 100-mL graduated cylinder.
Measure 50 mL of water and add it come the alcohol in the 100-mL i graduated cylinder.
The full volume that the liquid will certainly be around 97 or 98 mL. This is surprising because 50 mL that water + 50 mL that water amounts to 100 mL.
Explain come students that when the water and alcohol molecule interact, they rearrange and actually take it up less room than if you add up your individual volumes.
Note: friend may have actually heard the explanation the the water molecules room in the spaces in between the alcohol molecules or the alcohol molecules room in the spaces between the water molecules. This is also passive one explanation. It’s not prefer marbles falling in the spaces in between golf balls. There is an energetic rearranging of molecules that room attracted to one one more that results in the final volume. In fact, adding any 2 liquids that have the right to dissolve in one one more will an outcome in a volume that’s various from the sum of the different liquid volumes. Alcohol and also water are regularly used as an example of this phenomenon since they are straightforward to get and show a particularly large difference.