Lesson Plan

Elements, Compounds, and Mixtures

  • Grade Levels
    8th Grade
  • Related Academic Standards
  • Assessment Anchors
  • Eligible Content
  • Big Ideas
    • A technological world requires that humans develop capabilities to solve technological challenges and improve products for the way we live.
    • Each area of technology has a set of characteristics that separates it from others; however, many areas overlap in order to meet human needs and wants.
    • Technological design is a creative process that anyone can do which may result in new inventions and innovations.
    • Technological literacy is the ability to use, assess and manage technology around us.
    • Technology is created, used and modified by humans.
  • Concepts
    • A technological design & problem solving process changes ideas into a final product or system.
    • Bio-related technologies are the processes of using biological mater to make or modify products.
    • Bio-related technologies are the processes of using biological organisms to make or modify products.
    • Communication is the process of composing, sending, and receiving messages through technology.
    • Communication is the process of composing, sending, and receiving messages using technological devices.
    • Construction is the process of turning materials into useful structures.
    • Construction is the process of turning raw materials into useful structures.
    • Decisions about the use of products and systems can result in expected and unexpected consequences.
    • Energy and power technologies are the processes of converting energy sources into useful power.
    • Energy and power technologies use processes to convert energy into power.
    • In a technological world, inventions and innovations must be carefully assessed by individuals and society as a whole.
    • Innovation is the process of improving an existing product, process, or system.
    • Innovation is the process of modifying an existing product, process, or system to improve it.
    • Invention is a process of creating new products, processes, or systems.
    • Invention is a process of turning ideas and imagination into new products, processes, or systems.
    • Inventions and innovations must be carefully assessed by individuals and society.
    • Manufacturing is the process of turning materials into useful products.
    • Manufacturing is the process of turning raw materials into useful products.
    • People select, create, and use science and technology and are limited by constraints (e.g. social and physical).
    • People select, create, and use technology.
    • Safety is a preeminent concern for all technological development and use.
    • Safety is one of the most important concerns for all technological development and use.
    • Science and technology are interconnected.
    • Technological design & problem solving follows many steps.
    • Technological design & problem solving includes clearly communicated solutions.
    • Technological design & problem solving includes frequent checking.
    • Technological design & problem solving requires hands-on applications.
    • Technological literacy is a lifetime endeavor.
    • Technological literacy is necessary for a productive 21st century skilled workforce.
    • Technological literacy is necessary for a productive workforce.
    • Technological literacy is necessary for all citizens.
    • Technological literacy is required for all citizens in a democratic society for shared decision-making.
    • Technological literacy is the ability to understand, use, assess, design, and create technology.
    • Technological literacy is the ability to understand, use, assess, design, and produce technology (i.e. Invention & Innovation).
    • Technological literacy requires lifelong learning.
    • Technology and society impact each other.
    • Technology and society mutually impact each other.
    • The abilities required in a technological world include diagnosing, troubleshooting, analyzing and maintaining systems.
    • The abilities required in a technological world include understanding, fixing, and maintaining systems.
    • The goal of technology is to meet human needs and wants.
    • Transportation is the process of safely and efficiently moving people and products.
    • Understanding technological systems help us plan and control technological developments.
    • While science is the study of the natural world, technology is the study of the human designed world.
  • Competencies
    • Create a new product, process, or system.
    • Describe and demonstrate how to use technological design & problem solving.
    • Describe how science and technology work together.
    • Design and develop the ability to create and send messages using technological devices.
    • Design and develop the ability to safely and effectively use tools and materials to build structures.
    • Design and develop the ability to safely and effectively use tools and materials to convert energy into power.
    • Design and develop the ability to safely and effectively use tools and materials to create bio-related products and systems using technology.
    • Design and develop the ability to safely and effectively use tools and materials to create vehicles that transport people and products.
    • Design and develop the ability to safely and effectively use tools and materials to manufacture products.
    • Design and produce solutions to technological problems.

Objectives

In this lesson, students will learn that all matter can be classified as either a pure substance or a mixture. They will also learn that both mixtures and pure substances can be broken down into subcategories and that there are techniques chemists use to determine in which category a sample of matter belongs. Students will:

  • classify a sample of matter in terms of pure substances and mixtures.

  • distinguish between homogenous and heterogeneous mixtures.

  • distinguish between solutions, colloids, and suspensions.

  • recognize the difference between an element and a compound.

Essential Questions

Vocabulary

  • Element: Pure substance consisting of one type of atom.

  • Compound: Pure substance consisting of two or more different atoms.

  • Mixture: Two or more different substances not chemically combined.

  • Colloid: A heterogeneous mixture that exhibits the Tyndall effect.

  • Suspension: A heterogeneous mixture that has particles large enough to settle out.

  • Solution: A homogenous mixture in which the particles are very small.

  • Tyndall effect: The scattering of light in a colloid.

  • Homogeneous mixture: A mixture with a uniform composition.

  • Heterogeneous mixture: A mixture with a nonuniform composition.

  • Element symbol: An abbreviation for an element’s name found on the periodic table.

  • Compound formula: Represents the combination of two or more elements in fixed proportions. Subscripts designate the number of atoms of each element.

Duration

90 minutes/2 class periods

Prerequisite Skills

Prerequisite Skills haven't been entered into the lesson plan.

Materials

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Related Materials & Resources

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Formative Assessment

  • View

    Students can be assessed on this lesson in the following ways:

    • After explaining the difference between elements and compounds, have students classify a list of pure substances. This will provide an opportunity to reteach the differences and similarities between elements and compounds.

    • Both students and teacher can monitor understanding of the lesson with the Mixtures vs. Pure Substances lab activity. Students will be able to revisit an earlier activity and apply their acquired knowledge. This activity allows for revision and reflection.

Suggested Instructional Supports

  • View
    Scaffolding, Explicit Instruction
    W:

    The main focus of this lesson is to be able to categorize all matter. Students learn the difference between a pure substance and a mixture. They will then be able to categorize a mixture as either a colloid suspension or solution. They are evaluated formatively based on their responses during guided instruction. They are formally evaluated on the worksheet.

    H:

    The lesson begins with several pictures of everyday objects that students are asked to categorize. They revisit their answers at the end of the lesson to see which answers were correct and which need to be revised.

    E:

    The more you can relate categorizing to real-life, everyday objects, the more students will see the chemistry connection and the importance of categorizing matter.

    R:

    Responses to student questions need to be more than simply yes/no answers. Students will apply lesson material upon completion of the worksheet. They also revisit the pictures at the beginning of the lesson.

    E:

    The worksheet at the end of the lesson provides an opportunity for students to show what they have learned. They are given time to reflect and revise their initial responses to five photos.

    T:

    At the beginning of the lesson, when students are asked to categorize everyday objects, they could work in small teams. Additionally, molecular-level representations are provided as extensions, which may support visual learners.

    O:

    This lesson is organized so that in the beginning students are asked to perform a task using their prior knowledge. The lesson moves to teacher-guided instruction, with demonstrations included. The lesson then asks students to revisit the determinations they made in the beginning, this time with more knowledge. Finally, students complete a summary worksheet.

Instructional Procedures

  • View
    l2-01safetynote.PNG

    Show the pictures of common mixtures and pure substances such as:


    l2-02mixtures.PNG

    Ask students to classify each photo as either a pure substance or a mixture. Write their answers down under each photo. Tell them that you will revisit these pictures at the end of the lesson and see if their answers change.

    Tell students, “In the last lesson you learned that all matter can be described using physical properties. We will now look at specific categories in which all matter can be classified. There are two major categories that encompass all matter: pure substances and mixtures.” Put the following definitions on the board:

    • Mixture: Two or more different substances that are not chemically combined and can be physically separated.

    • Pure substance: A substance that cannot be physically separated.

      Say, “Can anyone think of an example of a mixture?” If students give a pure substance as their answer, explain that it would not be a mixture because one cannot separate it using physical means. Tell them there are two types of mixtures:

    • Homogeneous mixture: A mixture with a uniform composition.

    • Heterogeneous mixture: A mixture with a nonuniform composition.

      Give examples of homogeneous mixtures, including: cola, coffee, and iced tea. Ask, “What do cola, coffee, and iced tea have in common? Focus on the way they look, rather than their function or ingredients.” Guide them to notice that all three homogenous mixtures look uniform throughout. They cannot see any particles floating or sinking. Say, “Notice that they all look alike. Just by looking at them, you may not even know they are made from more than one substance.” Follow that with, “If cola, coffee and iced tea are all examples of homogenous mixtures, what would a heterogeneous mixture look like?” Students may offer that heterogeneous mixtures will look like they are made of different substances. Say, “What about Jell-O? It looks uniform. Would it surprise you to know that Jell-O is not a homogeneous mixture? It is heterogeneous! We need to dive into more specific descriptions about mixtures. Heterogeneous and homogenous mixtures have subgroups. All homogenous mixtures are called solutions. Heterogeneous mixtures can be either colloids or suspensions.” The general rules are:

    • Heterogeneous mixtures (suspensions and colloids):

      • Suspensions do not look uniform throughout.

      • Suspensions have particles that are large enough to settle to the bottom and can therefore be filtered with a funnel and filter paper.

      • Colloids have medium-sized particles.

      • Colloids often look uniform throughout (like solutions).

      • Unlike solutions, colloids’ particles scatter light. This property is called the Tyndall effect.

    • Homogenous mixtures (solutions):

      • Solutions look uniform throughout.

      • Solutions have very small particles.

      • Solutions cannot be separated through basic filtration (funnel and filter paper).

      • Solutions’ particles are so small they do not scatter light.

      Demonstration

      Students may have a difficult time understanding the Tyndall effect. A demonstration works to alleviate this problem. Fill a flask with 1000 mL of water. Add 10 to 20 drops of milk. With the lights off, shine a laser (generic laser pointers work) through the flask. They will see the laser go through the colloid. This is proof that colloids scatter light. Do the same procedure with plain water. They will not see the laser light within the liquid.

      l2-03tyndall.PNG

      http://www.silvermedicine.org/dark_tyndal_with_h2o2.jpg

      Say, “Now that we have talked about mixtures, what about the other category of matter? Pure substances can also be further described as either compounds or elements.” Ask students to give you examples of elements. Refer them to the Periodic table. Define element on the board.

    • Element: Pure substance consisting of one type of atom.

    • Element symbol: An abbreviation for an element’s name, found on the Periodic table.

    Ask, “What do you have if you have more than one type of element?” Define compound on the board.

    • Compound: Pure substance consisting of two or more different atoms.

    • Compound formula: Represents the combination of two or more elements in fixed proportions. Subscripts designate the number of atoms of each element.

      Put the following list on the board and ask students to categorize each as either an element or a compound:

    • Calcium (element)

    • Calcium oxide (compound)

    • H2O (compound)

    • Na (element)

    • NaCl (compound)

    • Lithium nitride (compound)

    • Sodium (element)

      For students who might need additional practice, reinforce that compounds must have two or more different elements.

      Lab Activity

    Use the Mixtures vs. Pure Substances–Teacher sheet (S-8-5-2_Mixtures vs. Pure Substances Teacher.doc) to set up the Mixtures vs. Pure Substances lab and to correct and assess students’ work when they have finished the lab. Assign students to teams. Hand out Mixtures vs. Pure Substances–Student (S-8-5-2_Mixtures vs. Pure Substances Student.doc) to students. In their groups, they should complete the information table for the examples, giving a designation and reason for each.

    Extension:

    • For students performing above and beyond the standards, have them fill out a flowchart similar to the one shown at http://www.shschem.info/Classifying%20Matter.htm to help them organize information throughout the lesson.

    • Students requiring more practice with the standards may find it helpful to express the difference between a homogenous and heterogeneous mixture on a molecular level, as shown below. Students can use the pictures throughout the lesson as a reference or if needed, express answers and definitions in picture form, as shown below.

    l2-04colouredmixtures.PNG

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DRAFT 11/18/2010
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