Mixtures and Solutions Stations Lesson Plan by Clara Welch Based on FOSS & Kitchen Chemistry by John Bath, Ph. D. and Sally Mayberry, Ed. D. Overview: This lesson is a group of activities that may be used as demonstrations of as individual lessons. It covers all of the 5 th grad standards for mixtures and solutions. Suggested grade level(s): Grades 4-6 Concepts covered: Suspension, Saturation, Concentrations, Properties of Matter: Separating Mixtures, Bleaching colors, Chemical reactions, Invisible Space. Standards: Physical Science IV Length of lesson: 10 min. Demonstration or 50 min. lesson Materials required: Materials listed for each activity below. Cost varies. STATION 1 Making a Suspension Background: A mixture occurs when two solids are placed together, such as salt and pepper. A mixture can also be a solid and a liquid (such as sugar and water), or two liquids (such as water and vinegar). Sugar dissolves in water forming a special mixture called a solution. A mixture is called a solution when the solid dissolves in the liquid. The liquid is called the solvent and the solid is called solute. A suspension occurs when the particles of a substance are dispensed throughout a liquid but not dissolved in it. An emulsion is a type of suspension that occurs when one liquid is suspended in another. How can you make a suspension? 4 Clear Plastic jars with lids ¼ cup of vinegar 1 teaspoon of paprika ¼ cup water ¼ cup salad oil 1. Mix oil and water in a jar and label the jar. 2. Mix oil and vinegar in a jar and label the jar 3. Mix oil, vinegar, and water in a jar and label the jar 4. Mix oil, vinegar, paprika and water in a jar and label the jar 5. Let students shake and observe each of the four jars. Page 1 of 7
Oil and water will mix only when shaken. As soon as you stop shaking the jar, the oil will float to the top of the water, forming a second layer. Oil and vinegar will also only mix when shaken. As soon as you stop shaking the jar, the oil will float to the top of the vinegar, forming a second layer. Water and vinegar will mix to form a solution, but the oil will not mix. As soon as you stop shaking the jar, the oil will float on top of the water and vinegar mixture, forming a second layer. Paprika, oil, water, and vinegar result in an emulsion. The paprika breaks down oil particles and keeps the oil in suspension. The oil particles are so small they stay suspended in the vinegar. This is not a solution because the oil and water will still separate. Critical Thinking Questions: What did you observe in each of the four jars? What is a mixture? Which jars contain mixtures? Why? What is a solution? Which jars contain solutions? Does the oil mix with any of the other liquids? Look carefully at the jar with paprika. What do you observe that might help you explain how the oil mixes with the water and vinegar? STATION 2 Removing Color with Bleach How can you use chemicals to make color disappear? 2 Clear plastic cups Water Food coloring Bleach Marbles Sand Note: This is a good as a teacher demonstration only since bleach can discolor clothing. 1. Pour water in the clear plastic cup until it is about one-half full. 2. Add two or three drops of food coloring. 3. Mix the water and food coloring. 4. Add bleach with an eyedropper until the color disappears. Page 2 of 7
The color will disappear from the water. Bleach releases chlorine. The chlorine combines with hydrogen in the water, releasing oxygen. The oxygen combines with the color to from a colorless compound. Critical Thinking Question: Are there any colors that the bleach will not remove? Will bleach remove color from things other than colored water? Variation: Prepare two clear plastics cups. Place water and a few drops of food coloring in the first cup. In the second cup, place enough bleach to cover the bottom, but not enough to be noticeable. You can tell students that the colored water changes to clear water simply by being poured into the second cup. Then bleach will remove the color from the water when it is poured into the empty cup. STATION 3 Invisible Space How can you show that water is full of holes? 1 cup of water 1 cup of rubbing alcohol 4 cup container 1. Measure exactly one cup water and exactly one cup of rubbing alcohol. You must measure very carefully and show students the accurate measurements. 2. Pour all of the water into a four cup container. 3. Have students guess what will happen when you add one cup of alcohol to one cup of water. 4. Pour all of the rubbing alcohol into the water. 5. Measure the total volume of the water and the alcohol. You will find that you have less than 2 cups of liquid. In this case 1 + 1 does not equal 2. Critical Thinking Question: Why doesn t one plus one equal two? Does any water or alcohol evaporate? How do you know? What would happen if you poured one cup of water into one cup of water? Try it. What would happen if you poured one cup of alcohol into one cup of alcohol? Try it. Where does the alcohol go when poured into 1 cup of water? Extension: Page 3 of 7
Remind students that materials are made of small particles we cannot see. Remind them that we have seen evidence in earlier experiments that these particles move. These particles have empty spaces among them. Water is full of tiny, invisible holes. Particles of water are always moving and there are spaced in between them. Rubbing alcohol particles fit in between the water particles. You can show this with marbles and sand. One cup of marble (very large particles) and one cup of sand (very small particles) will not equal two cups of matter when they are poured into the same container STATION 4 Concentration Introduction: When a soft drink solution tastes sweet and looks dark, it is a concentrated solution. When it tastes weak and looks light, it is a dilute solution. Concentration refers to the amount of material dissolved in a measure of liquid. The more material dissolved in a given amount of liquid, the more concentrated the solution. How much soft-dink powder mixed with 1 liter of water makes a good-tasting drink? 4 clear pitchers 1 liter beaker 1 measuring scoop Soft-drink powder 1 container of drinking water. Sampling cups 1. Place one liter of drinking water in each clear pitcher and label them 1, 2, 3, & 4. 2. Add one scoop of powder to pitcher #1, 2 to #2, etc. 3. Stir until powder is dissolved as much as possible. 4. Observe color and clarity of each solution. 5. Taste from each sample and record observations. The lighter color solution is weaker and should taste Critical Thinking Question: Which solution did you like the most? The least? What would happen if you decreased the amount of water but used the same amounts of powder? What is your recommended recipe for the soft-drink? Comments: Take a poll of the class s drink concentration preference. Have the students graph the data. Page 4 of 7
STATION 5 Separating Mixtures Part 1 How can you separate a mixture of gravel and water? 5-ml spoon Measuring cup/syringe 50-ml 2 cups Wire screen Gravel 1. Prepare cups with one level spoon, (50-ml) of Gravel in a cup. 2. Observe the material. 3. Add 50-ml of water to the cup. 4. Stir with wooden stick and observe. Record observations 5. Place empty screen over a second cup. 6. Pour the mixture through the screen filter. 7. Record results in chart. The mixture separates. The water falls into the second cup and the gravel remains on the wire screen filter. Comments: See last page for recording charts and Critical Thinking Questions for Separating Mixtures 1, 2, & 3 STATION 6 Separating Mixtures Part 2 How can you separate a mixture of diatomaceous earth and water? 5-ml spoon Measuring cup/syringe 50-ml 2 cups Coffee filter Diatomaceous earth Stirrers Filter stand Page 5 of 7
1. Prepare cups with one level spoon, (50-ml) of earth in a cup. 2. Observe the material. 3. Add 50-ml of water to the cup. 4. Stir with wooden stick and observe. Record observations 5. Place coffee filter in the filter stands and place over a second cup. 6. Pour the mixture through the coffee filter. 7. Record results in chart. The mixture separates. The water falls into the second cup and the diatomaceous earth remains on the coffee filter. Comments: See last page for recording charts and Critical Thinking Questions for Separating Mixtures 1, 2, & 3 STATION 7 Separating Mixtures Part 3 How do you separate a mixture of salt and water? Hot plate Frying pan 5-ml spoon Measuring cup/syringe 50-ml 2 cups Salt Stirrers 1. Prepare cups with one level spoon, (50-ml) of salt in a cup. 2. Observe the material. 3. Add 50-ml of water to the cup. 4. Stir with wooden stick and observe. Record observations 5. Pour mixture in frying pan. Carefully place pan on heated hot plate. 6. Boil solution until all water has evaporated. 7. Record results in chart. The mixture separates. The water will evaporate leaving the salt in the pan. Comments: See last page for recording charts and Critical Thinking Questions for Separating Mixtures 1, 2, & 3 Page 6 of 7
Critical Thinking Questions: What is a mixture? Give some examples. What is a solution? Give some examples Is salt and water a mixture? A solution? Is it both a mixture and a solution? How do you know when a solid and a liquid form a solution? How can mixtures be separated? How are screen filter and paper filters alike? How are they different? Observations Color Texture Particle shape Gravel Earth Salt Particle size Other Results Gravel Earth Screen Filter Paper Salt Page 7 of 7