Cellular Respiration - Follow-up

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Objective

Students will be able to understand the main idea of cellular respiration.

Big Idea

Cellular Respiration makes energy from food.

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Purpose of Lesson:

The purpose of this lesson is to help the students get deeply into the equation so that they can get beyond the symbols and reach understanding.

 

Major Strategies to Watch for:

1) Candy manipulatives-  In this activity students use candy to make and rearrange molecules through a chemical reaction.

2) Shared Reading- A multi-day activity to give kids the skills to read complex texts on their own.

Ready...Set...Engage!

3 minutes

Learning Goal:  Understand the main idea of cellular respiration.

Opening Question: What are cells making in cellular respiration?  What type of cells would need that?

This question address one of the most common misconceptions that students hold onto about cellular respiration.  Students want to believe that ONLY animals do cellular respiration.  It is very difficult for them to understand that photosynthesis is the first step for plants but that they ALSO need to produce energy. 

Students record their opening question on their learning goal sheet and are ready to start class 3 min after the bell has rung.  I reward students who get started early with ROCK STAR SCIENTIST tickets.  

Follow the links to learn more about the beginning of class strategies and ROCK STAR scientist tickets.   

Hook

10 minutes

The purpose of this section is to get students interested in the class and ready to learn about cellular respiration. 

I start this section by explaining to students that we are studying a chemical reaction. Basically a chemical reaction is where you take some ingredients and you chemically change them into something else. I write the chemical reaction we are going to do on the board and ask kids what they notice about it.

This is a great time to get out the anchor chart on reading chemical equations and have students use the chart to try to decipher the equation. It doesn't matter if they aren't able to do it....it is just another piece of practice for them. 

I have students open their lab notebooks and write down what a chemical reaction is and the equation for this reaction. Then I tell them that I'm going to do a chemical reaction and have them draw a picture and write down what they noticed.

While the students write down the definition of reaction, I get my supplies ready for a simple reaction. For this demonstration I use baking soda and vinegar. Most of the kids have seen this reaction before, which makes it perfect for actually talking about!

I put the baking soda in a flask and hold the vinegar in a beaker. The students draw a picture of the REACTANTS and label them. Then, when the students are watching, I combine the ingredients into the flask.  

When the reaction is over the I talk about the reactants and products and the students draw pictures in their lab notebooks. At the end of the demonstration, I reiterate that chemical reactions CHANGE substances into new substances.

Focus

10 minutes

Today we are ready to do Day 2 of the shared reading on reading chemical equations. I'm choosing this strategy because my students struggled with understanding the chemical equation in the previous unit and I want to give them a strong foundation for this unit.  

Shared reading is a great reading strategy to use when your goal is not only to help students with specific content, but also help them read a specific genre type. In this situation, we are "reading" chemical formulas. The big idea of shared reading is to gradually dig deeper and deeper into a complex text over a number of days, all the time exposing your own thinking to the students. A sample plan for shared reading might look like this.

Day 1- Preview the text and notice text features

Day 2- Comprehend the text using questioning, determining importance, visualization, or clarifying

Day 3- Extend the text using summation, inference, or synthesis

For this lesson, my job is simply to expose them to the text and my thinking, while allowing them to do some thinking. 

For Day 2 of shared reading, I am choosing to focus on visualization because I think that this strategy will go nicely with the demonstrations we are doing today and help the student visualize the reaction.

Before we get started on the visualization, I have the students write the equation down again in their lab notebooks and I pull the equation up on the screen.

Once the students are ready, I remind them of what we have learned about chemical reactions, reactants and products. We look at the anchor chart we made yesterday and remember some of the key features.  Then I tell the kids that one strategy scientists use when they can't see something is to imagine what it would look like. I stress with the kids that this isn't REALLY what it looks like but simply a visualization. Then I ask them to close their eyes and I visualize the reaction in my mind.  

A screencast of what this might sound like is below.

Unable to display content. Adobe Flash is required.

Once I have finished my visualization, I then ask the kids to do their own imagining of what this might look like and draw it in their notebooks under the equation. Finally, I ask the students to share how visualization changed their understanding of the reading.

Collaborative

20 minutes

The purpose of this section is to have the students collaboratively make the molecules involved in the chemical reaction using candy. This is a fun, if messy activity! 

The first thing to do is to pick out the candy you need. I like to use:

-Jelly Beans for hydrogen

-Gumdrops for oxygen

-Gummy bears for carbon

I put a variety of different  candies in a cup at the desk. The students have to figure out how many they need for each molecule and how many molecules of each they will have and what process they will follow. I have students do this in groups of four to speed the process up.

Then each group gets four pieces of paper that are labelled with the reactants and products for the equation. (Sugar, oxygen, water,carbon dioxide) The students should lay out the paper in order showing the equation. Then they will use the candy to make the molecules for the REACTANTS only.  During this time I walk around using praise-prompt -leave to help students build their molecules.

Once all the reactants are made I stop the kids and ask some questions.

1.  How did you know how many pieces of candy to use for each molecule?

2.  How did you know how many molecules to make?

At this point I take away all of the extra candy on the table. I want them to make the products using the atoms they made the reactants with. This reinforces the idea that chemical reactions rearrange atoms into new substances.

Then I tell the students that they need to make the products. This part generally goes very quickly as students have figured out how to physically make the candy molecules. When they have correctly put the molecules together I give them an "ATP post it" to represent the energy produced. If the students aren't able to put the molecules together correctly, they don't get any of the ATP. When the students are done I ask them these questions.

3.  Where did you get the material to make the products?

4.  What would happen if you didn't have enough sugar or enough oxygen?

Below are shots of the reactants and products of this activity!

Reactants

Products

Closure

2 minutes

Closing Statement:  "Today we looked at how chemical reactions change ingredients into products and we made our own cellular respiration equations out of candy.  Tomorrow we will be starting our lab on cellular respiration."

Closing Question: "How did this activity show us that the chemical reaction rearranges the atoms to make new products?"


Closure depends greatly on timing and is not as easy to plan in advance as opening.  You can find more information about how I manage closure here.