What "Eggs-actly" Is Going On Here?

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Objective

SWBAT diagram and analyze how matter has density.

Big Idea

What is density? How does it relate to me? Students investigate the concept of density through several hands-on interactions.

Engage - Draw What You Saw

10 minutes

Engage - Draw What You Saw

This bell ringer will get students thinking about density and how it affects their lives.  Students will get supplies, draw what they saw, and analyze the changes that occurred, and draw on the worksheet  Give students the supplies: beaker with water, spoon, small paper cup filled with table salt, hard boiled egg (shhh....don't tell them it's hard boiled), and a paper towel.  Provide the data sheet so that they can draw what they saw.  This bell ringer is an engaging, hands-on activity to start the class.

During the bell ringer, pose these questions:

  1. The position of the egg changed at some point. Describe the changes that occurred after adding the salt. Student responses: The egg rose when the salt was added. The egg started to float and not sink.
  2. Why do you think the changes occurred? Discuss all possible answers with the class. Student responses: The salt made the water more dense than the egg. The changes occurred because the salt changed the density of the water.

Now, relate the bell ringer to their lives.  Read this story to the class and engage in a discussion.

Story: Your family is undecided about where to spend summer vacation. Usually your family takes a vote, with each member casting one vote. The choice is between a cabin at a mountain lake or a trip to the seashore. Your younger brother likes to swim, although he does not swim very well. He will however cast the deciding vote. Apply what you've learned today with the egg and help your brother make a wise choice!

I circulate the classroom as students are discussing possible answers to the story. After one (1) minute, I ask students to share their ideas. Student responses should include: I should take my brother on vacation to the seashore because it is saltwater at the seashore and he will float, like the egg.

*Reference The 5E Instructional Model from NASA which describes a teaching sequence for lessons and/or units. The 5E's represent 5 stages of a sequence for teaching and learning: Engage, Explore, Explain, Extend (Elaborate), Evaluate.

KWL

5 minutes

KWL

This is the part of the lesson that helps students activate background knowledge, make connections, and provides me with feedback. I ask the students "What do you know about density?" and "What do you want to know about density?" They process their thoughts, write answers on the worksheet, and then share out with the whole class. It is important to share thoughts with the class so that students can hear other student's thinking.

Then I go on to explain why I want to know about density. I tell them my story.

My story: I like to go to Colorado to visit my brother. He lives in the mountains at an elevation of above 5,000 feet. When I go there, I have to understand about density. As you increase altitude, the density of the air becomes thinner, and this thinner or less dense air then exerts less pressure. So the higher, the altitude the less dense the air pressure. The pressure decreases, until in space - there is no air, no density, no pressure. This increased altitude affects cooking in the kitchen, from boiling an egg to baking cookies, to roasting a turkey. So I have to understand about density at different elevations in order to adjust my cooking in the kitchen!

NGSS: MS-PS1-4. Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed. **This lesson is working towards this standard!  Students must first understand that all matter has physical and chemical properties and that adding or removing thermal energy can change matter. Students will discover that density is one of many physical properties of matter. 

Explore - Popcorn Hop

20 minutes

Explore

As students further explore the concept of density, they (SP#1) ask questions and write an hypothesis, and use background knowledge about carbonation to relate that to the investigation. Students create a chemical reaction (SP#2) or model, similar to one occurring in soda and use the model to make popcorn kernels hop. As students explore, they (SP#3) carry out the investigation, (SP#4) interpret data to recognize patterns in the data, (SP#6) construct explanations as they (SP#8) evaluate and communicate information

I ask students to discuss with their peers and develop an hypothesis for the question "What makes the popcorn hop?"

One student hypothesis:

I think that chemical reactions will make popcorn hop because of the carbonation in the liquid.

Students go through the guided inquiry (as I've selected the overarching question), wait, and watch the popcorn kernels hop.

Explain

5 minutes

Explain

At this point in the lesson, I ask students to use their new knowledge, expand on the concepts learned in the lesson, and make connections to related concepts of matter and physical properties. I encourage students to apply an understanding of the world around them, discuss with their peers, and explain their answers to the questions. These questions will deepen their thinking about the concept of density.

I circulate the classroom and provide opportunity for students to discuss the questions with their peers. I want students to (CCC#4) use models to represent systems and their interactions and to represent a system (density) under study. Models can be used for understanding and predicting the behavior of systems. As students discuss questions and write answers, they MS-PS1-2 analyze and interpret data on the properties of substance before and after the substance interacts to determine if a chemical reaction has occurred (vinegar & baking soda).

Student responses:

1. What do you observe happening? I notice that the kernels start to rise and on the kernels there are bubbles. They are also bouncing.

2. Explain what you see in terms of a chemical reaction. I see that the vinegar and baking soda reacted and then formed bubbles and fizzing.

3. What are some signs of a chemical reaction. Some signs of a chemical reaction are fizzing, bubbles, sound, color change.

Evaluate

5 minutes

Evaluate

I ask students to complete the KWL by writing a conclusion to the question "What did you learn about the concept - Density?" I build rigor into the writing by asking students to use a sentence frame as they reflect on the learning. The sentence frame I learned that . . .because . . . adds depth to the writing for all students, especially ELL and Special Education students.

Students learned that:

. . . vinegar & baking soda react to make the popcorn kernels float because it makes bubbles and the bubbles make the popcorn kernels less dense and float.

As a culminating part of the learning, students share out their thoughts and reflections with the class. I ask students to share their conclusion so that students can hear other student thoughts and answers. To draw all students into the conversation, I use popsicle sticks. This strategy, built into the culture of my classroom, is random, engages all students, and provides equity.