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Activity 3 Solutions, Suspensions, and Colloids

Activity 3 Solutions, Suspensions, and Colloids

CS_Ch6_MovieSpEffects 2/24/05 10:24 PM Page 338

Movie Special Effects

Activity 3 , Suspensions, and

GOALS What Do You Think? In this activity you will: One way to get different types of materials is to just mix them • Explore different ways that together. Lots of different things can happen when materials materials can be mixed are mixed. Each kind of has its own characteristics. together to make new materials. • Is it easier to separate from coffee or milk from • Test some materials to a bowl of cereal? determine what kinds of they are. Record your ideas about this question in your Active log. Be prepared to discuss your responses • Determine why certain kinds of with your small group and the class. mixtures are manufactured for commercial use in particular Safety goggles and a lab apron situations. Investigate are required for this activity. 1. Half-fill six large test tubes with . Number the Wipe up spills test tubes. immediately. Report any broken or a) In your Active Chemistry log, prepare a table for cracked your observations. You may wish to use a table glassware to similar to the one on the following page. your teacher.

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Activity 3 Solutions, Suspensions, and Colloids

No. Materials mixed Observations Observations Kind Filter with water before mixing after mixing #1 water only #2 0.5 g #3 drops of milk #4

3. Stopper each test tube. Place your finger over the stopper and shake each for several minutes to make a mixture. Observe each mixture. 4. Consider the following characteristics of the mixtures: • What is the appearance of each mixture after the vigorous mixing? Which ones have visible suspended in them? Which ones look totally uniform (homogeneous) throughout? water • Which mixtures separate (are heterogeneous) after sitting a few moments after vigorous mixing? Which remain mixed? • Shine a laser pointer through each mixture. In which mixtures is the laser beam clearly visible? Never look 2. Add the following materials to the In which mixtures does it pass directly at a test tubes: through with little effect? laser beam. #1—nothing • For each mixture place a small #2—0.5 g sugar beaker below a funnel to catch the #3—a few drops of milk filtrate, as shown in the diagram on the next page. Pour the contents of #4—0.5 g CuSO4 (copper sulfate) #5—2 mL olive each test tube into a funnel with filter paper. Which mixtures pass #6—0.5 g through? Which leave part behind a) Describe each material before on the filter paper? mixing.

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Movie Special Effects

a) Record all your observations in the table in your log. b) Using your data and the descriptions of the kinds of mixtures in the ChemTalk reading section, classify each of the funnel mixtures as a , , or . 5. Discard materials and return all equipment as directed by your teacher. Clean up your station and wash your hands.

CLASSIFYING MIXTURES In this activity you mixed together water and several different materials to produce different kinds of mixtures. In some cases the Chem Words materials you used were pure substances. A pure substance pure substance: a contains only one kind of throughout. For example, sugar is a substance that contains only one kind of particle. pure substance.A mixture contains at least two pure substances.You solution: a homogeneous may think of water as a pure substance, however most water found in mixture of two or nature has different materials mixed with it and is in fact a mixture. more substances. solute: the substance Mostly all materials that you find in nature, as well as most human- that dissolves in a made materials are mixtures of one or more pure substances.You to form a solution. made one kind of mixture, called a solution, when you added sugar solvent: the substance in to water. In a solution, the particles that dissolve are so tiny they can’t which a solute dissolves to form a solution. be seen with the naked eye.The mixture is said to be homogeneous. The dissolved particles (called the solute) remain mixed forever with the solvent.The water, since it is doing the dissolving in this case, is the solvent. If a solution is filtered, everything passes through. Light passing through a solution has no special effect. When you added milk to water, the water appeared cloudy. However, the tiny drops of milk remained suspended in the water and did not

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Activity 3 Solutions, Suspensions, and Colloids

settle out over time.You could see the laser beam as it passed through the mixture, and when you filtered the mixture, it all passed through the filter paper.This kind of mixture is a colloid. In colloids, Chem Words the dispersed particles are larger than those in solution and may colloid: a mixture containing particles larger be visible on close inspection with a microscope.The particles will than the solute but small also stay suspended indefinitely.All parts of the colloid will pass enough to remain through a filter.When light passes through a colloid it is scattered suspended in the continuous of and you can see where the light beam passes through.This is known another component. This as the . is also called a colloidal . When you added soil to water, you created a suspension. Tyndall Effect: the Suspensions have the largest of all the dispersed particles.The of a light beam as it passes through particles are visible to the eye and will settle out in time.The a colloid. suspended particles can be separated by .The mixture is said suspension: to be heberageous.A light beam shining through a suspension may be heterogeneous mixture scattered, but the suspension is definitely not transparent. that contains fine or particles in a fluid that will settle out spontaneously. By shaking the container they will again be dispersed throughout the fluid.

Checking Up 1. In your own words describe how you would distinguish among a solution, a colloid, and a suspension. 2. What is the Tyndall Effect?

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Movie Special Effects

Reflecting on the Activity and the Challenge In this activity you made mixtures with to give an eerie setting. Many movies solid or liquid solutes and water as the have used the Tyndall Effect to show the solvent. The same basic principles apply path of laser beams or flashlights. One regardless of the states of easy way to produce this effect is to use involved. For example, it is possible to a spray bottle of water to mist the air in have solid solutions. alloys such a darkened room (problem with as brass or bronze are such solutions. allergies/asthma). When a flashlight or , , and clouds are mixtures laser pointer is directed through the that show the Tyndall Effect. A common mist, it shows up nicely, thanks to the stage effect is to produce smoke or fog Tyndall Effect.

1. Classify each of the following as a 3. On some days it is possible to see suspension, colloid, or solution. rays of light from the Sun distinctly Explain your reasoning. (Hint: In coming through breaks in clouds. some cases more than one answer What in the atmosphere might may be possible.) account for this difference? a) A mixture is poured through a 4. The term homogeneous means filter, and the entire mixture passes uniform or the same throughout. through. Heterogeneous means that different parts of the mixture are clearly b) A mixture is left to stand for a visible. Classify each of the mixtures while and small particles settle in this activity as homogeneous or out. heterogeneous. c) When viewed under a microscope, 5. Look in your kitchen at home and small particles are visible in the choose five products. Make your best mixture. guess as to the type of mixture they d) A beam of light passed through represent. Elaborate on the evidence the mixture is scattered. that you used to classify the products into the respective category. Explain e) The mixture is and what would happen to each product transparent. that you have chosen if it were in a 2. Suggest a method by which you different kind of mixture. For could separate the various materials example, milk would settle if it was a in each of the following mixtures: suspension instead of a colloid. a) solutions b) colloids c) suspensions

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Activity 3 Solutions, Suspensions, and Colloids

Preparing for the Chapter Challenge Consider how you could use the In a paragraph or two describe the properties of a solution, colloid, or chemistry required to understand the suspension to produce a special effect differences between the different types for a movie scene. In a few sentences of mixtures and how they produce the establish the setting for the scene, and special effect. describe the mood you want to create.

Inquiring Further

Cooking and mixtures as ? How could emulsions be used in a movie special effect? is a practical application of mixtures. in cooking utensils are also examples of mixtures. Investigate the One such application is the recipe for kinds of materials used in making metal making . Mayonnaise is cooking utensils. Why are some mixtures classified as a colloid. A liquid—liquid more suitable for cooking than others? colloid is also called an . If you have access to the following materials, try making mayonnaise at home. A Recipe for Mayonnaise Combine in a blender: 2 tablespoons beaten egg

Do this only 1 large egg with the 1 approval of a 4 teaspoon dry responsible adult. 1 teaspoon lemon juice Blend the mixture for 20 seconds. While the blender is still running, add 3/4 cup of vegetable oil slowly in the thinnest stream you can manage. Serve immediately or keep for 1 to 2 days in the refrigerator. Investigate the properties of the ingredients of mayonnaise that allow them to form this colloidal emulsion. What other substances are classified

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