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Lesson 5 - Other Examples of Combustion

Students learn to distinguish organic from inorganic materials and practice explanations of combustion for other organic materials. They also take the unit posttest.

Guiding Question

What is the difference between materials that burn and materials that don’t burn?

Activities in this Lesson

Note: Activity 5.2 is optional depending on your knowledge of your students and learning goals. If your students can already explain what happens to matter and energy when methane burns at an atomic-molecular scale, you may want to skip these portions of activities. See the Systems and Scale Unit Read Me file for more information to consider when making this choice.

  • (Optional) Activity 5.1: Molecular Models for Methane Burning (40 min)
  • (Optional) Activity 5.2: Explaining Methane Burning (40 min)
  • Activity 5.3: Preparing for Future Units: Organic vs. Inorganic (40 min)
  • Activity 5.4: Explaining Other Examples of Combustion (50 min)
  • Activity 5.5: Systems and Scale Unit Posttest (40 min)

Unit Map

Unit Map for Lesson 5

Target Performances

Lesson 5 – Other Examples of Combustion (students as explainers)

(Optional) Activity 5.1: Molecular Models for Methane Burning (40 min)

Students use molecular models to explain how carbon, oxygen, and hydrogen atoms are rearranged into new molecules during the oxidation of methane (the chemical change that happens when methane burns).

(Optional) Activity 5.2: Explaining Methane Burning (40 min)

Students explain how matter moves and changes and how energy changes when methane burns (connecting macroscopic observations with atomic-molecular models and using the principles of conservation of matter and energy).

Activity 5.3: Preparing for Future Units: Organic vs. Inorganic (40 min)

Students distinguish between organic and inorganic materials on the basis of both their functions (organic materials include foods, fuels, and the bodies of living things) and the chemical structure of their molecules (organic materials contain high-energy C-C and C-H bonds).

Activity 5.4: Explaining Other Examples of Combustion (50 min)

Students explain how matter moves and changes and how energy changes when other organic fuels burn, including (a) wood burning in a fireplace, (b) propane burning in a gas grill, and (c) octane burning in an internal combustion engine.

Activity 5.5: Systems and Scale Unit Posttest (40 min)

Students show their end-of-unit proficiencies for the overall unit goal: Questioning, investigating, and explaining how matter and energy changed during combustion of organic materials.

 

NGSS Performance Expectations

Middle School

  • Structures and Properties of Matter. MS-PS1-1. Develop models to describe the atomic composition of simple molecules and extended structures.
  • Chemical Reactions. MS-PS1-2. Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
  • Chemical Reactions. MS-PS1-5. Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.

High School

  • Chemical Reactions. HS-PS1-4. Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
  • Chemical Reactions. HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
Three-dimensional Learning Progression

In this final lesson of the unit, students have completed the inquiry and application sequences for the combustion of ethanol. The activities in the previous lessons were designed to walk students through a cognitive apprenticeship model of Establishing the Problem, Modeling, Coaching, and Fading. The results of the unit posttest will help you determine if your students are ready to move on to the final stage: Fading. After the Fading stage, students will be expected to carry forward concepts from this unit into future units. If the results from your posttest imply that a majority of your students are still struggling with certain concepts, it might be valuable to return to some of the main concepts they are struggling with before moving on to the next Carbon TIME unit.

Key Ideas and Practices for Each Activity

Activities 5.1 and 5.2 are the Coaching phase of the Application Activity Sequence, which provides students with important less-scaffolded practice with combustion. Students should take more responsibility for their work than in lesson 4, which included the Modeling phase. Students answer the Three Questions for burning methane using the Explanations Tool, coordinating accounts at the macroscopic and atomic-molecular scales. Macroscopic scale accounts (represented here by the Zooming into a Flame) include these components:

  • the structure of the system (the flame in this case) and the movement of materials through the system;
  • the location where chemical change takes place;
  • the materials involved in the chemical change: the reactants going in and the products coming out.

Atomic-molecular scale accounts include three different ways of representing chemical change:

  • molecular models, with twist ties to represent units of energy, that students use to physically rearrange the atoms of the reactants into the atoms of the products;
  • a chemical equation that shows how atoms are rearranged into new molecules in a compact way (but does not account for energy);
  • the Explanations Tool, which provides a way for students to account for changes in matter and energy in writing but answering the Three Questions.

Activity 5.3 provides students with additional important Foundational Knowledge and Practice (in the Application Activity Sequence) about the fundamental difference between organic and inorganic materials. These two types of material are different in terms of:

  • Origins: All the living organisms on Earth (foods and fossil fuels) have organic materials and originated in living organisms;
  • Chemical energy: Organic materials have more chemical energy;
  • Molecular structure: Organic materials have C-C and C-H bonds.

Activity 5.4 is the Fading phase of the Application Activity Sequence for combustion. It serves as formative assessment for you—you will be able to see how well they understood the ethanol example—and gives students additional practice explaining examples with less support than they had for ethanol and methane.

Activity 5.5 includes summative assessment for the unit. You can track students’ progress by having them take the Unit posttest (identical to the unit pretest) and comparing the results of the two assessments.

Key carbon-transforming processes: combustion

Content Boundaries and Extensions

This lesson of the unit represents the fading portion of the Explanations Phase. This means that students are expected to develop explanations for carbon-transforming processes they studied in this unit in new and novel contexts. The table below shows specific talk and writing goals for the Explanations phase of the unit.

Talk and Writing Goals for the Explanations Phase

Teacher Talk Strategies That Support This Goal

Curriculum Components That Support This Goal

Examine student ideas and correct them when there are problems. It’s ok to give the answers away during this phase! Help students practice using precise language to describe matter and energy.

Let’s think about what you just said: air molecules. What are air molecules?

Are you talking about matter or energy?

Remember: atoms can’t be created. So that matter must have come from somewhere. Where did it come from?

Let’s look at the molecule poster again… is carbon an atom or a molecule?

Molecule Poster

Three Questions Poster

 

Focus on making sure that explanations include multiple scales.

The investigation gave us evidence for what was happening to matter and energy at a macroscopic sale. But what is happening at an atomic-molecular scale?

What is happening to molecules and atoms?

How does energy interact with atoms and molecules during chemical change?

Why doesn’t the macroscopic investigation tell us the whole story?

Let’s revisit our scale poster… what is happening to matter at the molecular scale?

Molecular Models

Molecular Modeling Worksheets

Explanations Tool

PPT Animation of chemical change

Powers of Ten Poster

Encourage students to recall the investigation.

When did this chemical change happen during our investigation?

How do we know that? What is our evidence?

What were the macroscopic indicators that this chemical change took place?

Evidence-Based Arguments Tool

Investigation Video

Elicit a range of student explanations. Press for details. Encourage students to examine, compare, and contrast their explanations with others’.

Who can add to that explanation?

What do you mean by _____? Say more.

So I think you said _____. Is that right?

Who has a different explanation?

How are those explanations similar/different?

Who can rephrase ________’s explanation?

Explanations Tool