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Content Benchmark P.12.A.3
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Students know identifiable properties can be used to separate mixtures. E/S

All of our daily activities involve recognizing, evaluating and using physical properties. From selecting the clothes we wear to the food we eat, we are using, evaluating and sorting based on physical properties. If it is warm outside, we select lighter colored, and lighter weight clothing rather than dark, heavy, wool type materials. We intuitively evaluate the insulating properties of the clothes as well as the interaction of the clothing fibers with the energy of the sun. Similarly, we select our foods the same way evaluating color, texture, smell and freshness. We are not apt to select foods to eat that are beginning to rot. We bring our childhood experiences of knowing that some materials are repelled by magnets while some are attracted and others do nothing at all. We also learn early that metal containers become hot when warm liquids are poured into them while as other materials to a lesser degree. We know that metals tend to be shiny and warm up in the sun while non-metallic materials do not have the shiny quality. Physical properties are part of our everyday experience.

Physical properties are characteristics of a material that can be measured. They are properties that do not change the chemical nature of matter. Some physical properties vary with the amount of the material such as volume, size, and mass. These physical properties are called extensive physical properties. Some properties do not change with the amount of the material and allow the material to be categorized and identified. These properties are called intensive physical properties and can include such characteristics color, odor, density, boiling point, melting point.

For more information about properties, please see,

and to learn more about the distinction between extensive and intensive properties, go to

Physical properties are important to understand when trying to separate mixtures. There are two types of mixtures that scientists considered: homogeneous and heterogeneous. This content standard focuses on heterogeneous mixtures and the uses of physical properties to separate them. Heterogeneous mixtures are composed of different substances (compounds or elements) that remain separate and distinct. A very common example used in physical science classrooms is a mixture of sulfur and iron filings. Using the magnetic property of iron, a simple magnet will pull the iron filings away from the sulfur and the mixture has been separated.

For more information about heterogeneous mixtures please see, and

Examples of Separation Techniques

An excellent presentation which covers the most widely used separation techniques and their practical uses can be found at the following website.

Figure 1. Examples of separation of solid-solid mixtures.

For example, these M&M’s can be separated based on their color differences.

Figure 2. Color differences in candy can be used as an analogy for separating solid-solid mixtures.

Figure 3.This columns contain oil and water and can be separated based on the density differences between the two different liquids.

Figure 4. Filtration is another method to separate a solid from a liquid

One interesting heterogeneous mixture is iron fortified cereal. The iron can be removed by mixing the cereal with water and then using a magnet to extract the iron.

Figure 5. Lab setup to separate solids from liquids using magnetism

Liquids can be separated from one another using a method known as distillation which is based upon the differences in the boiling points of the substances.

For more information on distillation please see,

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Content Benchmark P.12.A.3

Students know identifiable properties can be used to separate mixtures. E/S

Common misconceptions associated with this benchmark:

1. Students incorrectly think that “pure” substances mean without “harmful” components and many don’t recognize that pure substances mean unmixed substances.

It is important to separate experiential misconceptions from instructional misconceptions. Misunderstandings about the word “pure” can lead to much confusion. Inquiry activities designed to examine and provide evidence for conceptual understandings would lead to the dissolution of many of the above student notions. The students understand “pure” in terms of clean or without contamination. When defining an element, it is important to emphasize that an element is composed of one type of atom with its own set of properties. Additionally, some things look like “pure” substances to students but rather are often mixtures with multiple sets of properties. Assessing students prior to instruction will help guide the instructional activities.

To learn more about common misconceptions about science, go to

2. Students incorrectly believe that particles possess the same properties as the materials they compose.

Molecules, atoms, and subatomic particles make up all materials. Many students think that these particles have the same identifiable properties on the microscopic scale that do on larger, macroscopic scale. For example, students incorrectly think that atoms of copper are "orange and shiny", gas molecules are transparent, and solid molecules are hard.
To learn more about student misconceptions in chemistry go to

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Content Benchmark P.12.A.3

Students know identifiable properties can be used to separate mixtures.

Sample Test Questions

1st Item Specification: Distinguish between mixtures and compounds.

Depth of Knowledge Level 1

  1. Which of the following is considered to be a pure substance?
    1. Granite.
    2. Sodium chloride.
    3. Muddy water.
    4. Milk of Magnesia.
  1. Physical properties of a mixture
    1. vary with the amount of substance.
    2. depend on the volume of the substance.
    3. depend on the organization of the substance.
    4. vary depending upon its components.
  1. Examples of physical properties that depend on the quantity of a substance include
    1. boiling point, color.
    2. color, density.
    3. melting point, solubility.
    4. volume, mass.
  1. Mixtures
    1. can have the same composition throughout.
    2. have physical properties dependent on its components.
    3. have the same physical properties as compounds.
    4. cannot be separated into their components.
  1. Compounds
    1. are the same as mixtures.
    2. can be separated by their physical properties.
    3. contain only one type of element.
    4. are different kinds of atoms chemically combined with each other.

Depth of Knowledge Level 2

  1. White gold is used in jewelry and contains two elements, gold and palladium. A jeweler has two different samples that are both identical in appearance and have a uniform composition throughout. What can be said about the samples?
    1. They are homogeneous mixtures and be classified as metallic alloys.
    2. The materials are heterogeneous mixtures and can be classified by their components.
    3. The samples have variable compositions and are classified as metallic solutions.
    4. The samples are heterogeneous mixtures that can be separated using magnetic properties.
  1. A student is given an unknown substance and asked to perform paper chromatography to determine whether it is a mixture or a pure substance. She placed several drops of the substance on the paper. Her results are below.


She concludes that

  1. she has a mixture because multiple bands of color are evident.
  2. she has one substance only because the top of the paper is blue.
  3. the experiment is inconclusive because the bands are different.
  4. chromatography is not a good method of separating substances.
  1. When a pure solid substance was heated, it changed into another solid and a gas, each of which was a pure substance. Based on these observations, the original solid
    1. was not a single element.
    2. was a compound.
    3. is a compound and the products are elements.
    4. was a mixture of two other substances.
  1. A brass alloy contains 66 % copper and 34 % zinc. It is best described as
    1. a pure substance because it contains blended elements.
    2. a compound because it contains two different types of atoms.
    3. a solution because it has the same composition throughout.
    4. separable because copper and zinc have different conductivities.

2nd Item Specification: Distinguish between heterogeneous and homogeneous mixtures.

Depth of Knowledge Level 1

  1. Which of the following is an example of a heterogeneous substance?
    1. Bottled water
    2. Table salt
    3. Pieces of copper
    4. Candle
  1. Which of the following is an example of a heterogeneous substance?
    1. Calcium carbonate
    2. Sodium sulfate
    3. Aspirin
    4. Salad dressing
  1. Which of the following is an example of a homogeneous substance?
    1. Teflon
    2. M&M candy
    3. Vitamin water
    4. Red Kool–Aid beverage
  1. Which of the following is an example of a homogeneous substance?
    1. Granite
    2. Table salt
    3. M&M candy
    4. Muddy water
  1. Which of the following is an example of a homogeneous substance?
    1. Glass
    2. Dirt
    3. Flowers
    4. Ice cream sundae
  1. Which of the following is an example of a homogeneous substance?
    1. Green tea
    2. Sandwich
    3. Chocolate Chip Cookie
    4. Pine cone

Depth of Knowledge Level 2

  1. Which of the following contains a homogeneous mixture?

  1. Sample A
  2. Sample B
  3. Sample C
  4. Sample D
  1. Which of the following diagrams shows a heterogeneous mixture?

( From

  1. Diagram a, b and c
  2. Diagram a and c
  3. Diagram b, c and d
  4. Diagram a and b
  1. Which of the following shows the correct example of a heterogeneous material?
    1. Mixture → same composition throughout → solution.
    2. Mixture → magnet → two separate substances.
    3. Mixture→ filtration → one substance.
    4. Air → wind → one solution of gases.
  1. Which flow chart correctly describes a homogeneous material?
    1. Unknown → density → 3 layers.
    2. Unknown → filtration → two substances.
    3. Unknown → magnet → two substances.
    4. Unknown → boiling → one temperature.

3rd Item Specification: Design separation processes based on properties (e.g., magnetism, solubility, density, boiling point, and properties that lend themselves to mechanical sorting).

Depth of Knowledge Level 1

  1. Filtration can be used to separate
    1. solids from solids.
    2. liquids from solids.
    3. liquids from liquids.
    4. liquids from gases.
  1. One common method used to separate dyes is
    1. filtration.
    2. distillation.
    3. chromatography.
    4. conductivity.
  1. Melting points can separate materials because
    1. substances melt at different temperatures.
    2. molecules vibrate rapidly when heated.
    3. heat causes molecules to disintegrate.
    4. many substances fuse at the melting point.
  1. Distillation is a good separation technique for
    1. solids.
    2. liquids.
    3. solid alloys.
    4. gases.
  1. Solubility is a good separation technique for
    1. pure metals.
    2. noble gases.
    3. different salts.
    4. metallic alloys.
  1. Magnetism is most beneficial for separating
    1. gases and non-metallic liquids.
    2. magnetic solids and solids such as sulfur.
    3. non-metallic solids and solids such as sulfur.
    4. non-magnetic solids from non-magnetic liquids.

Depth of Knowledge Level 2

  1. The following graph was made of two liquid being distilled. What observation can be made regarding point B?

What observation can be made regarding point B?

  1. The first liquid component is boiling.
  2. The second component has already boiled.
  3. The mixture is homogeneous.
  4. Energy is being removed from the liquid.
  1. A student has three unknown solid metals. Which series of tests would be the MOST appropriate to use to distinguish among the metals?
    1. Boiling point, density and color.
    2. Color, density and mass.
    3. Density, mass and volume.
    4. Conductivity, density and color.
  1. A student has a mixture of sand, water, salt and iron pieces. Which procedure would separate the mixture?
    1. Evaporate the water, use a magnet to remove the iron.
    2. Filter the water to separate the sand, use a magnet to remove the iron.
    3. Filter the sand and iron from the water, use a magnet to remove the iron from the sand, evaporate the water to separate the salt.
    4. Filter the sand and iron from the water; evaporate the water to separate the salt.
  1. Which of the following observations could be used to separate two metals?
    1. Bubbles form when the substance is dropped into water.
    2. The color of both metals is grey.
    3. One metal is attracted to a magnet.
    4. The volumes of the metals are different.

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Content Benchmark P.12.A.3

Students know identifiable properties can be used to separate mixtures.

Answers to Sample Test Questions

  1. B, DOK Level 1
  2. D, DOK Level 1
  3. D, DOK Level 1
  4. B, DOK Level 1
  5. D, DOK Level 1
  6. A, DOK Level 2
  7. A, DOK Level 2
  8. B, DOK Level 2
  9. C, DOK Level 2
  10. D, DOK Level 1
  11. D, DOK Level 1
  12. B, DOK Level 1
  13. B, DOK Level 1
  14. A, DOK Level 1
  15. A, DOK Level 1
  16. D, DOK Level 2
  17. A, DOK Level 2
  18. B, DOK Level 2
  19. D, DOK Level 2
  20. B, DOK Level 1
  21. C, DOK Level 1
  22. A, DOK Level 1
  23. B, DOK Level 1
  24. C, DOK Level 1
  25. B, DOK Level 1
  26. A, DOK Level 2
  27. D, DOK Level 2
  28. C, DOK Level 2
  29. C, DOK Level 2

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Content Benchmark P.12.A.3

Students know identifiable properties can be used to separate mixtures. E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. Mixtures and Solutions Information Clearinghouse
The Science, Technology, and Children Web site has a section that covers mixtures and solutions. This site is a clearinghouse that lists many educational and professional organizations that discuss mixtures in detail. This site is an excellent resource for student research into mixtures.

To access the mixtures and solutions site, to

2. Mixture Basics
Rader’s site has two sections that discuss mixtures. This site includes general information with a True-False quiz that students can use to check their knowledge.

To access the mixture site, go to

3. Physical Properties Lesson
The American Chemical Society has developed a lesson that allows students to explore the physical properties of matter. This lesson can be downloaded at
/ACS/ACSContent/education/wande/ resourcechem/matter/Matter_Act_2.pdf

4. Chemistry Activities Listing
Lapeer County, Michigan has an excellent site serving as a Science Resource Center. Their chemistry activities listing includes demonstrations, labs, and teaching tips. This site has been acknowledged by the National Science Teachers Association as SciLinks site.

You can check out the site at

5. Chemistry Activities and PowerPoint Presentations
Mr. Allan, a science teacher at El Diamante High School in Visalia, California, has created a site that with a large variety of activities, PowerPoint presentation, and other resources. The site is located at

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