Skip to Content

Plants | Lesson 3 - Investigating Plants

Lesson 3: Investigating Plants

Students conduct an investigation about plants in the light and dark. The focus of this lesson is to make observations and prepare data to be used as evidence for their explanations in Lesson 5. Students will harvest their plants to either estimate their dry masses and/or prepare them to be dry-massed later.

Guiding Question

What happens when plants are left in the light and in the dark?

Activities in this Lesson

  • Activity 3.1: Predictions About Plant Investigations (50 min)
  • Activity 3.2: Observing Plants in the Light and Dark (60 min)
  • Activity 3.3: Evidence-Based Arguments About Plants in the Light and Dark (20 min)


Gel Protocol (2-turtle)

  • Activity 3.4GL: Observing Plants' Mass Changes, Part 1 (45 min)


Paper Towel Protocol (2-turtle)

  • Activity 3.4PT: Observing Plants' Mass Changes, Part 1 (45 min)

Objectives

  1. Detect changes in carbon dioxide concentration caused by plants in the light and in the dark.
  2. Construct arguments that use evidence about mass gain in plants and carbon dioxide concentration in the air to defend claims about movements of atoms and chemical changes during plant growth and functioning.
  3. Find patterns in data collected by multiple groups about changes in mass or gas exchange in plants.
  4. Draw and explain movements of materials during 1) time that plants are in light and 2) time that plants are in the dark, including molecules that enter the plant, air enriched in carbon dioxide, and water vapor leaving the plant.

NGSS Performance Expectations

Middle school

  • MS. Structure and Properties of Matter. MS-PS1-1. Develop models to describe the atomic composition of simple molecules and extended structures.
  • MS. 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.
  • MS. 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.
  • MS. Matter and Energy in Organisms and Ecosystems. MS-LS1-7. Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism.
  • MS. Matter and Energy in Organisms and Ecosystems. MS-LS2-3. Develop a model to describe the cycling of matter and flow of energy among living and non-living parts of an ecosystem.

High school

  • HS. 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.
  • HS. Chemical Reactions. HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
  • HS. Energy. HS-PS3-1. Create a computational model to calculate change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.
  • HS. Structure and Function. HS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
  • HS. Matter and Energy in Organisms and Ecosystems. HS-LS1-5. Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

Background Information

This lesson provides students with experiences to observe and to collect data which will support them in their next lesson when they construct their explanations about photosynthesis and cellular respiration. They will observe that plants “breathe” (i.e., exchange gases with air) differently in the light and in the dark.

This lesson includes a PEO (Predict-Explain-Observe) Inquiry Activity Sequence with the final E (Explain) occurring in the next lesson. We will consistently focus on the idea that understanding carbon-transforming processes involves answering the Three Questions:

  • The Matter Movement Question: Where are molecules moving? (How do molecules move to the location of the chemical change? How do molecules move away from the location of chemical change?)
  • The Matter Change Question: How are atoms in molecules being rearranged into different molecules? (What molecules are carbon atoms in before and after the chemical change? What other molecules are involved?)
  • The Energy Change Question: What is happening to energy? (What forms of energy are involved? What energy transformations take place during the chemical change?)

The investigations in all units will make use of two essential tools:

  • Digital balances. Students can detect movement of atoms (the Matter Movement Question) by measuring differences in mass. This Activity will ask students to harvest their plants to prepare for future dry-massing.
  • Bromothymol blue (BTB). This is a liquid indicator that changes from blue to yellow in response to high levels of CO2. Thus changes in BTB can partially answer the Matter Change Question by detecting whether there is a chemical change that has CO2 as a reactant or product.

Activity 3.1 is the Predictions Phase of the instructional model (beginning the climb up the triangle). During this phase, students record their predictions and express ideas about what happens to plants when they are in the light and the dark as well as where a plant’s mass comes from as it grows. They use the Predictions Tool to do this.

Activity 3.2 is the Observations Phase of the instructional model (going up the triangle). During this phase, the students conduct the investigation for plants in the light and in the dark, record data, and try to identify patterns in their data and observations. The important practices students focus on in this activity are 1) making measurements and observations, 2) recording their data and evidence, and 3) reaching consensus about patterns in results. They use the Observations Worksheet and Class Results Poster to do this.

Activity 3.3 the Evidence-Based Arguments Phase of the instructional model (going up the triangle). During this phase, the students review the data and observations from their investigation of plants in the light and in the dark and develop arguments for what happened during the investigation. In this phase, they also identify unanswered questions: at this point they have collected data and observations about macroscopic scale changes (BTB color changes), but they do not have an argument for what is happening at the atomic-molecular scale. They use the Evidence-Based Arguments Tool to record their arguments at this phase.

Activity 3.4 will set up the Observations Phase of the instructional model for Lesson 5. During this activity, the students will harvest their radish plants. If you are following the 2-turtle Gel Protocol, students will collect wet mass in 3.4 and set up to collect dry mass later in Lesson 5. If you are following the 1-turtle Paper Towel Protocol, students will collect dry mass only in Activity 3.4.

A note on mass and weight: Grams and kilograms in the SI (metric) system are units of mass—the amount of matter in a system. On the other hand, pounds and ounces in the English system are units of weight—the force of gravity on a particular mass. As long as gravity doesn’t change, these units are interconvertible: The force of gravity on a 1 kg mass is about 2.205 pounds. Since most American students are more familiar with the English units of weight, we sometimes use “weigh” and “weight,” especially when encouraging students to express their own ideas. When referring to measurements in grams, we use “mass” as both a verb and a noun.

Key Carbon-Transforming Processes: Photosynthesis

Unit Map

Plants Lesson 3 Unit Map

Talk and Writing

At this stage in the unit, the students will complete the inquiry sequence for Plant Investigations—they will go up the triangle. This means they will go through the Predictions Phase, the Observations Phase, and the Evidence-Based Arguments Phase. The tables below show specific talk and writing goals for these phases of the unit.

Talk and Writing Goals for the Predictions Phase

Teacher Talk Strategies That Support This Goal

Curriculum Components That Support This Goal

Treat this as elicitation and brainstorming (like the Expressing Ideas Phase), but with more directed questioning.

Now that we have set up the investigation, we want to predict what we think will happen to matter and energy.

Three Questions Handout

Predictions Tool

Elicit a range of student ideas. Press for details. Encourage students to examine, compare, and contrast their ideas with the ideas of other students.

Who can add to that?

What do you mean by _____? Say more.

So I think you said _____. Is that right?

Who has a different idea?

How are those ideas similar/different?

Who can rephrase ________’s idea?

Investigation Video (selected sections)

Encourage students to provide evidence that supports their predictions.

How do you know that?

What have you seen in the world that makes you think that?

 

Have students document their ideas to revisit later.

Let’s record our ideas so we can come back to them and see how our ideas change.

Predictions Tool

 

Talk and Writing Goals for the Observations Phase

Teacher Talk Strategies That Support This Goal

Curriculum Components That Support This Goal

Help students discuss data and identify patterns.

What patterns do we see in our data?

How do you know that is a pattern?

What about ______ data. What does this mean? 

Class Results Poster

Class Results Spreadsheet

Encourage students to compare their own conclusions about the data and evidence with other groups and other classes.

What about this number? What does this tell us?

How is group A’s evidence different from Group B’s data?

How do our class’s data differ from another classes’ data?

Class Results Spreadsheet

Class Results Poster

Investigation Video (selected segments)

Make connections between the observations and the data/evidence.

It says here that our BTB turned colors. What does that mean?

You recorded that your plant gained mass. What does that mean?

 

Have students consider how their predictions and results compare.

Let’s revisit our predictions. Who can explain the difference between our class predictions and our results?

Who had predictions that were similar to our results? Has your explanation changed? How?

 

 

Talk and Writing Goals for the Evidence-Based Arguments Phase

Teacher Talk Strategies That Support This Goal

Curriculum Components That Support This Goal

Press for details. Encourage students to examine, compare, and contrast their ideas with the ideas of other students.

Who can add to that argument?

What do you mean by _____? Say more.

So I think you said _____. Is that right?

Who has a different argument?

How are those arguments similar/different?

Who can rephrase ________’s argument?

Investigation Video (second half)

Students provide evidence from the investigation (not just experiences in the world) to develop arguments.

Does your argument include evidence from the investigation?

What evidence is most important here?

What does this evidence tell us about what happened?
What evidence do we still need for a complete picture of what happened?

How do you know that?

Evidence-Based Arguments Tool

Class Results Poster

Class Results Spreadsheets

Investigation Video (second half)

Data from other classes

Focus on how matter and energy were transformed at different scales.

 

What does this evidence tell us about how matter is changing?

What does this evidence tell us about how energy is changing?

 

Three Questions Handout

Evidence-Based Arguments Tool

 

Revisit predictions and examine change in thinking.

Let’s revisit our Predictions and see how our thinking changed now that we know what happened.

Evidence-Based Arguments Tool

Predictions Tool

Encourage students to consider the questions they don’t have answers to.

This investigation told us many things about what happen to matter and energy during ____. But what questions do we still have?