Mixtures

Designed by: Margaret Knight          School:   Gibbes Middle School

Grade Level:  6     Subject(s): Science

Core Curriculum Objective(s): Characteristics of Matter and Energy/ Matter has characteristic properties that are related to its structure. Students will investigate and understand how to classify materials as elements, compounds or mixtures.  (6ME-1) 

Overview:   Students will classify mixtures by their properties as heterogeneous mixtures, solutions, suspensions, or colloids.

Focus/Essential Question(s):  How can you determine if an unknown mixture is a heterogeneous mixture, a suspension, a solution, or a colloid?

Time Frame: (2) 50 minute class periods

Bibliography:  Teachers Leading Teachers,  Physical Science activities for teachers in grades 4-9. Developed by the 1995 cohort of lead teachers. University of South Carolina. 

Materials: flashlight, copper sulfate, vinegar, 1/2 tsp. measuring spoons, alcohol, alum, sand, sugar, Epsom salt, corn starch, gelatin, clear plastic cups or small jars, ammonia, boric acid, distilled water, blue food coloring, powdered milk, salt, chalk dust, Kool Aid, iron fillings, goggles, rubber gloves, aprons

Culminating Assessment: Students will create a data sheet using the computer and answer two summary questions about the lab.

Instructional Activities: The teacher will prepare ahead the red cabbage juice indicator. The cabbage should be boiled until soft. The juice is then drained and placed into a container. The teacher may want the students to first discover that there are differing colors produced from the chemical reaction and make inferences from their observations. The teacher may opt to explain how the color of a material is caused by the chemical structure interacting with the light waves which are either absorbed or reflected. The red cabbage juice will turn green in the presence of a base. The base causes a change in the chemical structure of the cabbage juice so it transmits more green light waves. More red light waves are transmitted in the presence of an acid. 

1) Students will work in pairs. 

2) Fill a plastic cup 2/3 full of distilled water. 

3) Measure out 1/4 teaspoon of any one of the test materials and add it to the distilled water in the cup. 

4) Stir the material in the distilled water for two to three minutes. Observe. 

5) Cover the cup with a lid or piece of cardboard and set the cup in a place where it can remain undisturbed for several hours. 

6) Repeat steps 1-5 for the testing of ___ more items. (Your teacher will select the number of items to be tested.) 

7) With your partner, use the computer to create a data chart which includes all materials being tested, whether the material settles out or scatters light, observations, and identification of the mixture. 

8)*Next class period* After several hours have passed, examine the materials in the cups of distilled water. In the chart record your observations as to the presence of visible particles in the bottom of the cup. 

9) Shine a beam of light through the material in the cup. Examine and record on the chart if the beam of light is clearly visible in the liquid. 

10) Classify the liquid in the cup as a heterogenous mixture, a suspension, a colloid, or a solution. Record this on the chart. 

11) Explain why you classified each test item as you did.

Answer the following questions: 

1. Explain in your own words how you could determine if an unknown mixture were a heterogenous mixture, a suspension, a solution, or a colloid.

2. Why do so many products have the word "Shake Well" on the label?

Rubric for grading data sheet and questions: 

1. The data table carries the appropriate data - 20 pts 

2. An appropriate title for the data table is provided - 20 pts 

3. The information in the data table columns is appropriately organized and labeled. - 20 pts

4. The data table has been properly constructed using Microsoft Works  or other appropriate computer program. - 20 pts

5. The answers to the two questions support the concepts with  accurate details and exhibit proper use of vocabulary, language mechanics, and complete sentences. - 20 pts 

Total_____________ 100 pts